statsei8 ss8 - 北京大学地球物理学系(geophysics ... · 16:00--18:00 arrival / registration...

The 8th International Workshop on Statistical Seismology

Program & Abstracts

Beijing, China

2013

S 8 S StatSei8

Beijing 2013

Contents

Program ............................................................................................................................................ 1

August 12th, 2013, Monday Morning ............................................................................................. 13

August 12th, 2013, Monday Afternoon ........................................................................................... 25

August 13th, 2013, Tuesday Morning ............................................................................................. 39

August 13th, 2013, Tuesday Afternoon .......................................................................................... 51

August 14th, 2013, Wednesday Morning ........................................................................................ 61

Poster Session ................................................................................................................................. 69

1

Program August 9th, 2013, Friday

16:00--18:00 Arrival / Registration for persons who participate Statsei8 Pre-workshop Tutorials

(Zhongguanyuan Global Village Lobby)

Pre-Workshop Tutorial: presented by the Community Online Resource of Statistical

Seismicity Analysis (CORSSA)"

August 10th, 2013, Saturday

Location: Room 2829(8th floor), Science Building #2, Peking University

07:00 – 09:00 Breakfast

(Second Floor of Zhongguanyuan Global Village)

09:50 – 10:00 Introduction

10:00 – 12:00 Lecture 1: A Prospect of Earthquake Prediction Research

by Prof. Yosihiko Ogata

12:15 Lunch

14:00 – 16:00 Lecture 2: Defining and Testing Hypotheses of Earthquake Nucleation and

Arrest

by Prof. David D. Jackson

2

August 11th, 2013, Sunday

16:00 – 18:00 Arrival / Registration for persons who participate Statsei8 workshop

(Zhongguanyuan Global Village Lobby)

18:00 Reception Dinner

(Second Floor of Zhongguanyuan Global Village)

August 12th, Monday

Morning

9:00 – 9:10 Opening address

Yuntai Chen (PKU)

9:10 – 9:30 Statistical seismology in old age – a grandfather’s view

David Vere-Jones (VUW)

9:30 – 9:45 Development of Statistical Seismology in China -- in memory of Prof Ma Li

Jianping Huang (IES, CEA)

Session 1 Physics related to earthquakes: Earthquake faults, triggered and induced

seismicity, repeating earthquakes

9:45 – 10:15 (I) Dynamics implication behind the Gutenberg-Richter law

Xiaofei Chen

10:15 – 10:35 Towards more realistic physics based seismicity models: role of afterslip and

secondary triggering

Camilla Cattania, Sebastian Hainzl, Frank Roth, Lifeng Wang

10:35 – 10:55 Coffee break

10:55 – 11:25 (I) Seismicity rate increase in the Tokyo Metropolitan area following the 2011 off

the Pacific coast of Tohoku Earthquake due to the Coulomb stress increase

Takeo Ishibe, Shin’ichi Sakai, Kunihiko Shimazaki, Kenji Satake, Hiroshi

Tsuruoka, Shigeki Nakagawa, and Naoshi Hirata

3

11:25 – 11:55 (I) M8 Kanto earthquakes likely triggered by large events off eastern Japan

between the Sanriku coast and the Boso Peninsula

M. Imoto and H. Fujiwara

11:55 – 12:15 Analysis of Induced seismicity after the 2011 Tohoku-Oki earthquake by

non-stationary ETAS models

Takao Kumazawa, Yosihiko Ogata

12:30 Lunch

Afternoon

Session 1 (Cont.) Physics related to earthquakes: Earthquake faults, triggered and

induced seismicity, repeating earthquakes

14:00 – 14:30 (I) Testing atmospheric and tidal earthquake triggering at Mt. Hochstaufen,

Germany

S. Hainzl, Y. Ben-Zion, C. Cattania, and J. Wassermann

14:30 – 14:50 Comprehensive understanding of reservior seismicity

Huai Zhang, Huihong Cheng, Yaolin Shi

14:50 – 15:10 Developing a statistical framework that governs finite earthquake source process

Seok Goo Song, Luis Angel Dalguer, and P. Martin Mai

15:10 – 15:30 Testing stress coupling in fault slip inversion

Lifeng Wang, Sebastian Hainzl, and Gert Zöller

15:30 – 15:50 Conditions and probability of through-going ruptures along a restraining

double-bend of the Altyn Tagh fault

Benchun Duan and Zaifeng Liu


16:10 – 16:30 How do aftershock parameters depend on local physical properties?

Olga Zakharova and Sebastian Hainzl

4

16:30 – 16:50 Spatio-temporal renewal model for repeating earthquakes and analysis of slip rate

on the upper surface of the subducting Pacific Plate

Shunichi Nomura, Naoki Uchida, and Yosihiko Ogata

16:50 – 17:20 (I) Kostrov method applied to repeating multiplets

Zhongliang Wu, Changsheng Jiang, Yutong Li, and Xiaojing Ma

17:20 –17:50 (I) Mechanism of spontaneous and triggered shallow creep events - Implications

for shallow fault zone properties

Meng Wei, Yoshihiro Kaneko, Yajing Liu, and Jeffrey J. McGuire

17:50 - 18:10 Statistical properties of low-frequency earthquakes triggered by large earthquakes

in southern Taiwan

Chi-Chia Tang, Zhigang Peng, Cheng-Horng Lin, Kevin Chao, and

Chau-Huei Chen

18:10 – 18:40 Discussion

18:40 Dinner

5

August 13th, Tuesday

Morning

Session 2: Development of models and methods

8:30 – 8:50 Estimating the statistical models of earthquake occurrences from the data of

incompletely detected earthquakes

Takahiro Omi, Yosihiko Ogata, Yoshito Hirata and Kazuyuki Aihara

8:50 – 9:10 Further Investigations into the ETAS Model

David Harte

9:10 – 9:30 On the stress release models with new tips from geophysics: Bayesian estimation,

forecasting and validation

Varini E, Rotondi R, Basili R, Barba S, Betrò B

9:30 – 10:00 (I) A Bayesian approach to estimate the periodic change in earthquake detection

capability and its applications to JMA catalogue

Takaki Iwata


Session 3: Earthquake predictability, precursors and tests

10:20 – 10:50 (I) Real-time foreshock discrimination

Yosihiko Ogata

10:50 – 11:10 The spatio-temporal evolution of seismic activity preceding and following the 5

September 2012 Nicoya Peninsula earthquake

Jacob Walter, Zhigang Peng, Xiaofeng Meng, Susan Y. Schwartz,

Andrew V. Newman, and Marino Protti

11:10 – 11:30 Test seismicity anomalies by using the ETAS model as null hypothesis

Jiancang Zhuang

11:30 – 11:50 Assessing the potential improvement in short-term earthquake forecasts from

incorporation of GPS data

Ting Wang, Jiancang Zhuang, Teruyuki Kato, and Mark Bebbington

6

11:50 – 12:20 (I) Temporal and spatial anomalies of seismo-ionospheric anomalies in the total

electron content associated with large earthquakes

J. Y. Liu, Y. C. Su, C. H. Chen, H. F. Tsai, and Y. I. Chen

12:30 Lunch

Afternoon

Session 3 (Cont.) Earthquake predictability, precursors and tests

14:00 – 14:20 Statistical analysis of microwave remote sensing data for earthquake related

thermal anomaly over the India-China border region

Suryanshu Choudhary and A.K. Gwal

14:20 – 14:50 (I) An ensemble seismic hazard model for Canterbury, New Zealand

Matt Gerstenberger

14:50 – 15:20 (I) Japanese earthquake predictability experiment with multiple runs before and

after the 2011 Tohoku-oki earthquake

Naoshi Hirata, Hiroshi Tsuruoka, Sayoko Yokoi

15:20 – 15:50 (I) A hybrid statistical/physical model for forecasting aftershock rates

Sandy Steacy, Matt Gerstenberger, Charles Williams, David Rhoades, and

Annemarie Christophersen

15:50 – 16:20 Coffee break and visiting posters

Session 4 Special session on the Lushan April 20, 2013, Lushan Ms 7.0 earthquake

16:20 – 16:40 Challenges of statistical seismology from the Lushan earthquake

Zhongliang Wu and Changsheng Jiang

16:40 – 17:00 Is the 2013 Lushan Ms 7.0 earthquake an aftershock of the 2008 Wenchuan Ms

8.0 earthquake on Longmenshan fault, Sichuan, China?

Ke Jia, Shiyong Zhou, Jiancang Zhuang, and Changsheng Jiang

17:00 – 17:20 Discussion of the predictability of Lushan M7.0 earthquake by Pattern

Informatics method

Yongxian Zhang and Xiaotao Zhang

7

17:20 – 17:40 Panel discussion

The April 20, 2013, Lushan Ms7.0/Mw6.8 earthquake and the seismicity gap in

the Southern Longmenshan fault zone

(Materials and scope please see Home Page)

Panelists: Shiyong Zhou, Zhang Yongxian, David D. Jackson, Zhongliang Wu


18:00 Dinner

8

August 14th, Wednesday

Morning

Session 5 Estimating maximum magnitude

9:00 – 9:30 (I) Magnitude Limits of Subduction Zone Earthquakes

Yufang Rong and David D. Jackson

9:30 – 10:00 (I) Common problems in estimation of seismic hazard source parameters and

their solution

Andrzej Kijko

10:00 – 10:40 Coffee breaks and visiting posters

10:40 – 11:10 (I) New Multiple Dimension Stress Release Statistic Model based on co-seismic

stress triggering

Shiyong Zhou and Mingming Jiang

11:10 – 11:40 (I) What can be learned from earthquake catalogs about the largest expected

magnitudes?

Gert Zöller, Matthias Holschneider, Sebastian Hainzl, Jiancang Zhuang


12:20 Lunch

Afternoon

Visiting Beijing National Earth Observatory (NEOBJI)

13:30 Departure

Collection: Zhongguanyuan Global Village Lobby

Take bus to the Beijing National Earth Observatory

14:30 - 15:30 Visit Jiufeng Seismic Station

16:00 - 17:30 Visit Beijing Seismic Station, Key Laboratory of Seismic Observation and

Geophysical Imaging (SOGI), and Technology Center of China Seismic Array

9

17:30 - 18:00 Supper: NEOBJI dining hall

18:00 Return to Zhongguanyuan Global Village

August 15th, Thursday

8:30-- 17:30 Geophysical Field Observation Trip

10

Poster Session

Moment Tensor Inversion Using Exact Calculated Green Function in Southeastern Iran

Mehdi Rastgoo, Habib Rahimi

Probability of occurrence from characteristic earthquakes in the Corinth Gulf, Greece, fault

system

Maura Murru, Giuseppe Falcone, Rodolfo Console, Vassilis Karakostas,

Eleftheria Papadimitriou, David Rhoades

Evaluation of statistical forecast models in the Corinth Gulf, Greece

Giuseppe Falcone, Maura Murru, Rodolfo Console, Eleftheria Papadimitriou,

Vassilis Karakostas, David Rhoades

Variation of b values with depth in Kanto region, Japan

Abhey R. Bansal, Tsuruoka Hiroshi,

On the macroseismic attenuation from the probabilistic perspective. Applications in European

countries

Rotondi R., Varini E., Brambilla C.

Three-dimensional earthquake forecasting model for the Kanto district

Sayoko Yokoi, Hiroshi Tsuruoka and Naoshi Hirata

Comparison of recent seismic hazard models based on the Gutenberg- Richter

magnitude-frequency relation

Zhang Xiaoliang, Wang Ji, Yang Caihong, Gao Zhanwu

Numerical simulations of postseismic processes of the 1992 M7.2 Landers earthquake with a

damage rheology model

Lifeng Wang, Vladimir Lyakhovsky, Yariv Hamiel, Yehuda Ben-Zion and

Matthias Holschneider

Evaluation of annual, global seismicity forecasts, including ensemble models

Matteo Taroni, Jeremy Zechar, Warner Marzocchi

Short-term foreshocks in Southern California and Italy as non-triggered events

Stefanie Seif, Arnaud Mignan and Stefan Wiemer

A statistical study on seismo-ionospheric anomalies of the total electron content associated with

worldwide large earthquakes during 1998–2012

Y. I. Chen, J. Y. Liu, C. H. Chen, H. F. Tsai

Assessment of completeness and homogeneity of aftershock catalogue of 2001 MW 7.7 Bhuj

earthquake

S.K. Aggarwal, B.K. Rastogi, P.K. Khan, A.R. Bansal and S. Kumar

Characteristics of seismicity clustering in Japan

11

Xiaowei Chen, Aitaro Kato

Statistical study of ULF seismo-magnetic phenomena at Kakioka Observatory

Peng Han, Katsumi Hattori, Maiko Hirokawa

How much information is in any 5-year CSEP test?

Matt Gerstenberger, Jeremy Zechar, David Rhoades

Sensitivity of aftershock rates for a Wellington fault earthquake to different parameters.

Annemarie Christophersen, David Rhoades and Sebastian Hainzl

Spatial variation of b-value and its tectonic implications

Yujie Zheng and Shiyong Zhou

Community Online Resource for Statistical Seismicity Analysis

J.D. Zechar, J.L. Hardebeck, A.J. Michael, M. Naylor, S. Steacy, S. Wiemer, and J.

Zhuang

12

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13

Abstracts

August 12th, 2013, Monday

Morning

9:00 - 9:10 Opening address

Yuntai Chen (PKU)

9:10 - 9:30 Statistical seismology in old age - a grandfather’s view

David Vere-Jones (VUW)

9:30 - 9:45 Development of Statistical Seismology in China -- in memory of Prof

Ma Li

Jianping Huang (IES, CEA)

Session 1 Physics related to earthquakes: Earthquake faults, triggered and


9:45 - 10:15 (I) Dynamics implication behind the Gutenberg-Richter law

Xiaofei Chen

10:15 - 10:35 Towards more realistic physics based seismicity models: role of

afterslip and secondary triggering

Camilla Cattania, Sebastian Hainzl, Frank Roth, Lifeng Wang

10:35 - 10:55 Coffee break

10:55 - 11:25 (I) Seismicity rate increase in the Tokyo Metropolitan area following

the 2011 off the Pacific coast of Tohoku earthquake due to the Coulomb

stress increase

Takeo Ishibe, Shin’ichi Sakai, Kunihiko Shimazaki, Kenji Satake,

Hiroshi Tsuruoka, Shigeki Nakagawa, and Naoshi Hirata

11:25 - 11:55 (I) M8 Kanto earthquakes likely triggered by large events off eastern

Japan between the Sanriku coast and the Boso Peninsula


14

11:55 - 12:15 Analysis of induced seismicity after the 2011 Tohoku-Oki earthquake

by non-stationary ETAS models


15

Statistical seismology in old Age - a grandfather’s view

David Vere-Jones

In this talk the speaker will outline the early history of the International Statistical

Seismology Workshops, referring in particular to the China-New Zealand link, and the

contributions of the late Professor Ma Li and her friend and colleague Professor Shi

Yaolin.

16

Development of statistical seismology in China -- in memory of Prof Ma

Li

Jianping Huang

17

Dynamics implication behind the Gutenberg-Richter law

Xiaofei Chen

18

Towards more realistic physics based seismicity models: role of afterslip

and secondary triggering

Camilla Cattania, Sebastian Hainzl, Frank Roth, Lifeng Wang A correlation between the static stress changes produced by an earthquake and the

location of its aftershocks has been observed in several studies, and the Coulomb stress

triggering hypothesis is the basis of physics based medium term earthquake forecasts. In

the original Coulomb stress triggering formulation, and in several currently used models,

only the few largest earthquake are included as stress sources, and the stress field is

assumed to remain constant with time after each mainshock: redistribution of stresses by

postseismic processes such as afterslip, viscoelastic relaxation and small aftershocks is

neglected. However, several lines of evidence suggest that both afterslip and aftershocks

play an important role in triggering subsequent earthquakes. The cumulative moment of

afterslip can be a significant fraction of the mainshock moment, producing stress changes

of comparable magnitude; moreover, the observed similarity between their temporal

evolution has led to the suggestion that aftershock triggering is governed by afterslip. The

stress changes induced by individual aftershocks are orders of magnitude smaller than

those due to the mainshocks, and hence aftershocks are often not included as stress

sources. However, stress changes from small events can be large in the near field, and the

cumulative contribution of small events can be significant: the clustering of aftershocks,

and the success of statistical models with cascade triggering (such as ETAS) suggest that

secondary triggering may be significant.

In this study, we test the effect of including afterslip and secondary triggering into

forecast models with seismicity evolution governed by the Rate-and-State constitutive

laws. We focus on two case studies: the Mw=6.0 Parkfield and the Mw=9.0 Tohoku

earthquakes. We compare a starting model, which only considers mainshock induced

stresses, with three models: one which also includes afterslip, one treating aftershocks as

stress sources, and one including both processes. Aftershocks are modeled as finite

sources when focal mechanisms are available, while a spherically symmetric stress field

is assumed when the focal mechanism is unknown. Preliminary results indicate that the

inclusion of afterslip and aftershocks improves model performance: for Parkfield, all

three models obtain higher LogLikelihood scores than the original model, with the one

including both processes performing best. In particular, we find that the inclusion of

afterslip gives a better description of the spatial distribution of aftershocks, especially in

regions which were unloaded coseismically and reloaded postseismically: these results

indicates that, given the complementary distribution of coseismic slip and afterslip, the

19

inclusion of both processes can be particularly important from an hazard point of view.

Overall, our results indicate that the redistribution of stresses by afterslip and by

aftershocks can play an important role in the evolution of aftershock sequences, and

modeling of these processes has the potential to improve medium term operational

forecasting models.

20

Seismicity rate increase in the Tokyo Metropolitan area following the

2011 off the Pacific coast of Tohoku earthquake due to the Coulomb

stress increase

Takeo Ishibe, Shin’ichi Sakai, Kunihiko Shimazaki, Kenji Satake, Hiroshi Tsuruoka, Shigeki

Nakagawa, and Naoshi Hirata

(Earthquake Research Institute, the University of Tokyo)

Seismicity rate increases in the Tokyo Metropolitan area following the 2011 off the

Pacific coast of Tohoku (Tohoku-oki) earthquake are basically well correlated with the

static changes in the Coulomb Failure Function (ΔCFF) imparted by the mainshock,

while some other possible factors (e.g., dynamic stress changes, excess of fluid

dehydration) may also contribute the rate changes.

In the Kanto region, where the Tokyo Metropolitan area is located, various types of

earthquakes occur due to the complex tectonics; the Philippine sea plate and Pacific plate

are subducting beneath the Kanto region from the south and east, respectively. To

consider the large variation in focal mechanism, the receiver faults for the ΔCFF were

assumed to be two nodal planes of small (M ≥ 2.0) earthquakes which occurred before

and after the Tohoku-oki earthquake.

Among 30,746 previous events provided by the National Research Institute for Earth

Science and Disaster Prevention (M ≥ 2.0, July 1979 - July 2003), we used as receiver

faults, about 16,000 events indicate significant increase in ΔCFF while about 8,000

events show significant decrease. Positive ΔCFF predicts seismicity rate increase in

southwestern Ibaraki and northern Chiba prefectures where intermediate-depth

earthquakes occur, and in shallow crust of the Izu and Hakone regions. In these regions,

seismicity rates significantly increased after the Tohoku-oki earthquake. The seismicity

has increased since March 2011 with respect to the Epidemic Type Aftershock Sequence

(ETAS) model (Ogata, 1988). The activated seismicity in the Izu and Hakone regions

rapidly decayed following the Omori-Utsu formula, while the increased rate of seismicity

in the southwestern Ibaraki and northern Chiba prefectures is still continuing.

We also calculated temporal changes in distributions of ΔCFF due to the Tohoku-oki

earthquake calculated for the nodal planes of focal mechanism solutions obtained from

the F-net and/or Metropolitan Seismic Observation network (MeSO-net), which had been

constructed in recent years. The ΔCFF values for the earthquakes after March 2011 show

21

more positive values than those before March 2011, supporting a triggering hypothesis

that the 2011 Tohoku-oki earthquake triggered the seismicity changes in the Kanto

region.

22

M8 Kanto earthquakes likely triggered by large events off eastern

Japan between the Sanriku coast and the Boso Peninsula


Only the 1923 and 1703 earthquakes in the Kanto region, central Japan, are widely

accepted as M8-class earthquakes that were caused by the relative motion between the

Philippine Sea Plate (PH) and the North American Plate (NA) along the Sagami trough.

These two events followed M8 earthquakes along the Japan Trench - where the Pacific

Plate (PA) is subducting beneath NA - in 1896 and 1677, respectively. Assuming a

Brownian passage time model based on historical earthquake data, we have simulated

earthquake sequences to determine whether these Kanto events were observed just by

chance following the Japan Trench megathrust earthquakes. It is not conclusive but

probable, at a significance level of 95%, that this historical evidence was not observed by

chance. Thus, we assume that a large earthquake along the Japan Trench can trigger an

M8 earthquake along the Sagami trough. This triggering could be interpreted as follows.

First, we assume that the stress regimes in the Kanto area and along the Japan Trench are

mainly governed by the relative motion between NA and PA. Beneath the Kanto area, the

relative motion between NA and PA is decomposed into two components along the

directions of relative motion between NA and PH, and PH and PA, respectively. If

motion between PH and PA could take place, the accumulated stress may be partially

released and at the same time the orientation of the resultant stress may be rotated toward

a direction compatible with the relative motion direction between NA and PH. Therefore,

an M8 Kanto earthquake becomes more probable by a relative movement between PH

and PA after the 2011 Tohoku earthquake (M9.0) along the Japan Trench.

23

Analysis of induced seismicity after the 2011 Tohoku-Oki earthquake by

non-stationary ETAS models


The epidemic-type aftershock sequence (ETAS) model is a stationary point process, and

provides a good fit to an ordinary seismic activity. Its poor fitting suggests that the

earthquake mechanisms are affected by changes in geophysical factors. Fault strength is

one of the fundamental factors in a seismogenic zone, and its temporal change can induce

nonstationary seismicity. Although changes in fault strength have been suggested to

explain various phenomena, such as the remote triggering of seismicity, there has been

almost no means of quantitatively monitoring this property in situ. For this purpose, we

extend the ETAS model for non-stationary cases. This allows the parameters to be

time-variant, which then describes anomalous features of the seismic activity. We prepare

Bayesian models, and apply them to the data from inland seismic swarm activities that

have been induced by the 2011 Tohoku-Oki earthquake of M9.0.

25

August 12th, 2013, Monday

Afternoon

Session 1 (Cont.) Physics related to earthquakes: Earthquake faults, triggered and


14:00 - 14:30 (I) Testing atmospheric and tidal earthquake triggering at Mt.

Hochstaufen, Germany

S. Hainzl, Y. Ben-Zion, C. Cattania, and J. Wassermann

14:30 - 14:50 Comprehensive understanding of reservior seismicity


14:50 - 15:10 Developing a statistical framework that governs finite earthquake source

process

Seok Goo Song, Luis Angel Dalguer, and P. Martin Mai

15:10 - 15:30 Testing stress coupling in fault slip inversion


15:30 - 15:50 Conditions and probability of through-going ruptures along a restraining

double-bend of the Altyn Tagh fault



16:10 - 16:30 How do aftershock parameters depend on local physical properties?

Olga Zakharova and Sebastian Hainzl

16:30 - 16:50 Spatio-temporal renewal model for repeating earthquakes and analysis of

slip rate on the upper surface of the subducting Pacific Plate

Shunichi Nomura, Naoki Uchida, and Yosihiko Ogata

16:50 - 17:20 (I) Kostrov method applied to repeating multiplets


17:20 -17:50 (I) Mechanism of spontaneous and triggered shallow creep events -

Implications for shallow fault zone properties

Meng Wei, Yoshihiro Kaneko, Yajing Liu, and Jeffrey J. McGuire

17:50 - 18:10 Statistical properties of low-frequency earthquakes triggered by large

earthquakes in southern Taiwan

26

Chi-Chia Tang, Zhigang Peng, Cheng-Horng Lin, Kevin Chao, and

Chau-Huei Chen


27

Testing atmospheric and tidal earthquake triggering at Mt.

Hochstaufen, Germany

S. Hainzl, Y. Ben-Zion, C. Cattania, J. Wassermann

Seismicity closely related to hydrological impacts has been observed in several locations

worldwide; particularly in intraplate areas where tectonic stressing rates are small.The

trigger mechanism is usually explained by a poroelastic response of the seismogenic crust

to surface water flux, leading to pore pressure changes at depth. To explain the

earthquake triggering in response of those small stress changes, however, the crust has to

be near a critical state in which other transient processes might be significant.One of the

prominent examples is the Mt. Hochstaufen in SW Germany, where seismicity is known

to vary seasonally. A previous analysis showed that the seismicity in 2002 was highly

correlated to model forecasts based on fluid diffusion and rate- and state-dependent

frictional nucleation. Here we revisit this case by accounting additionally for poroelastic

effects, as well as for thermoelastic and tidal stresses. We also test whether the model can

explain the observations of the subsequent eight years between 2003 and 2010.Our

analysis confirms that rainfall is the dominant driving force in this region. The model not

only fits the year 2002 activity very well, but provides with the same parameters a

reasonable fit to the subsequent period, with a probability gain of about 4 per event in

comparison to a time-independent Poisson model.

28

Comprehensive understanding of reservoir seismicity


Key Laboratory of Computational Geodynamics of Chinese Academy of Sciences,

University of Chinese Aademy of Sciences, Beijing 100049 China

Genesis of reservoir-induced earthquake (RIS) is an important problem and has drawn a

lot of attentions. A debate has lasted two years about if the Wenchuan earthquake is

related to impoundment of the Zipingpu Reservoir or not, since the reservoir is less than

10 km from the epicenter. In order to know the mechanism of RIS better, we firstly

calculate numerical solution of simple problems and compare them with analytical

solution as benchmark to guarantee sufficient accuracy of the numerical method in

calculation of Coulomb failure stress (ΔCFS). Secondly, we discussed the difference

between 2D and 3D. Then, by taking the consideration of the precise topography and

dynamic water level, a three-dimensional poroelastic finite element model was

constructed about Zipingpu reservoir. Finally, for comparison, we also applied the

poroelastic FEM to the ML5.7 earthquake in Aswan reservoir in 1981 and the Ms6.1

earthquake in Xinfengjiang reservoir in 1962, which is well accepted as the largest

reservoir-induced earthquake in China. Our primary results showed that: The values had

been exaggerated in 2D model. The results of 3D model is only 1/3 to1/4 of that of 2D

model. The magnitude of pore pressure is about several kPa or 0.1MPa. For Zipingpu

reservoir, the elastic effect of water weight makes the fault more stable, while the

diffusion effect makes the fault more dangerous. If permeability of faults is sufficient

high, the ΔCFS may be positive 1.0kPa. As for Xinfengjiang earthquake, the reservoir

impounding increases both the pore pressure and ΔCFS. The ΔCFS at the hypocenter was

0.7~3.0 kPa in different models. As for the Aswan reservoir, the pore pressure of the

hypocenter provided by the USGS is about 0.3 MPa during the meantime that the ML5.7

earthquake occurred and ΔCFS caused only by reservoir loads is negative and relatively

small compared with pore pressure. Comparing with the Ms6.1 earthquake triggered by

Xinfengjiang reservoir and Aswan ML5.7 earthquake, the occurrence of reservoir

triggered earthquakes is closely related to the background tectonic stress field and relative

rock strength.

29

Developing a statistical framework that governs finite earthquake

source process

Seok Goo Song (ETH Zurich, Switzerland), Luis Angel Dalguer (ETH Zurich, Switzerland), P.

Martin Mai (Kaust, Saudi Arabia)

Earthquake rupture is a complex mechanical process that can be formulated as a

dynamically running shear crack on a frictional interface embedded in an elastic

continuum. This type of dynamic description of the earthquake source process has been

well developed over the last couple of decades, and has greatly helped to understand the

physical nature of earthquakes. However, there is still a significant amount of uncertainty

in our understanding about earthquake sources that need to be explicitly considered

especially when generating future scenario events in simulation-based ground motion

prediction for seismic hazard and risk analysis. This requires the development of a

statistical framework for characterizing the finite-source rupture process and quantifying

its variability in a consistent way. To this end, we propose a stochastic model for finite

earthquake source process with a set of random variables (e.g., random fields) that

represent the spatial distribution of kinematic source parameters. Currently the random

field model is characterized in the framework of 1-point and 2-point statistics. The

stochastic model is also linked to the concept of pseudo-dynamic source modeling

(Guatteri et al. 2004) in the sense that it is formulated using kinematic parameters for

computational efficiency, but also constrained by both rupture dynamics and

observational data. Our previous studies show great potential in finite source

characterization and modeling with 1-point and 2-point statistics of source parameters

(Song & Somerville 2010; Song & Dalguer 2013). It may also help to scrutinize the

effects of earthquake source on near-source ground motion characteristics in a more

systematic and consistent way (Song et al. 2013). Statistical seismology turns out to be

very useful in understanding earthquake occurrence pattern in a statistical sense.

Developing a stochastic model that governs finite source process, we may be able to

improve simulation-based ground motion prediction methods, consequently

simulation-based seismic hazard and risk analysis, in a more consistent statistical

framework.

30

Testing stress coupling in fault slip inversion


The seismic cycle includes the interseismic, coseismic and postseismic phase. The large

earthquakes release the interseismically accumulated stress on the fault, and are followed

by stress relaxation processes in the postseismic phase. Based on the geodetic

measurements, the stress coupling in the seismic cycle can be investigated by interseismic

slip deficit, coseismic rupture and postseismic slip distributions. However, it is

well-known that the fault slip inversions based only on the measurements on the surface

are typically non-unique and subject to large uncertainties. In this study, we firstly

assume the existence of stress coupling in the seismic cycle, and then do the stress

constrained joint inversion in Bayesian approach (Wang et al., 2012) to invert either for

(1) interseismic slip deficit and coseismic slip or for (2) coseismic slip and postseismic

creep. Based on the modeling results, we evaluate if the assumed stress coupling is

reasonable and if the stress coupling is able to be reflected from the available geodetic

measurements. We take the earthquakes in the regions with well-instrumented network

(such as the 2004 M6.0 Parkfield earthquake, the 2010 M8.7 earthquake and the 2011

M9.1 Tohoku-Oki earthquake) as study cases.

31

Conditions and probability of through-going ruptures along a

restraining double-bend of the Altyn Tagh fault


(Department of Geology & Geophysics, Texas A&M University, College Station, TX 77845,

USA)

Fault segment boundaries, particularly large-scale complexity in fault system geometry

such as bends, stepovers, and branch junctions, often act as barriers to earthquake

ruptures and thus limit earthquake sizes for a given fault system. However, these segment

boundaries can be broken occasionally as evidenced by recent large earthquakes, which

makes estimation of the maximum magnitude of earthquakes on a given fault system

extremely challenging. Identifying physical conditions and understanding dynamic

processes for through-going ruptures across these structural complexities are critical for

seismic hazard analysis.

The Aksay bend along the active, left-lateral Altyn Tagh fault in Northwest China is a

200-km-long restraining double bend and stepover. The two fault strands are separated by

only 5 to 15 km along strike. In this study, we perform a multi-cycle dynamic analysis in

a 2D plane-strain framework. We use a finite element method to simulate co-seismic

dynamic rupture propagation on the 2D left-lateral strike-slip fault that is governed by a

slip-weakening friction law. We use a viscoelastic model with analytical solutions to

track fault stress evolution during inter-seismic processes. The viscous component in this

viscoelastic model allows heterogeneous fault stresses associated with structure

complexities that evolve spontaneously over multiple earthquake cycles to relax during

the interseismic process, due to off-fault deformation such as uplift/subsidence. Different

sizes of earthquakes, which correspond to different rupture lengths in the 2D model,

occur on the fault system over multiple cycles, including some through-going ruptures

that break through the double bend and stepover. Close examination of the initial stress

state suggests that these through-going ruptures occur when the initial shear stress along

most of the fault system approaches the initial yield strength (the product of the static

frictional coefficient and the initial normal stress), i.e., the entire fault system is critically

loaded (the critical status). Dynamic triggering on one strand at locations where the initial

shear stress is very close to the initial yield strength by a propagating rupture on the other

strand is a dominate feature in these through-going ruptures.

32

Many processes operating in nature but absent in the multi-cycle model may prevent the

fault system from reaching the critical status. We plan to perform dynamic rupture

simulations of individual earthquakes with stresses after the events of the above

multi-cycle simulation with a limited amount of interseismic loading/relaxation. We

expect to have a large number of earthquakes that occur before the system reaches the

critical status and nucleate (artificially) far away from the bend/stepover region, which

may allow us to perform a statistical analysis of probability of through-going ruptures

along the fault system that has not reached the critical status.

33

How do aftershock parameters depend on local physical properties?

Olga Zakharova, Sebastian Hainzl

Aftershock sequence triggering is one of the important aspects of the seismic hazard

assessment. Although many studies concerning the aftershock sequences have been

preformed in the field of seismic hazard, the relations of aftershock parameters with

respect to the tectonic regime are still not clear. In our research we focus on the local

physical properties of two aftershock sequences. In particular, we use the data sets of

Maule (subduction sone) and Parkfield (transform fault) sequences and investigate

dependencies between seismic coupling/seismic slip and aftershock parameters

(aftershock productivity parameters K and α; Omori decay c- and p-value; b-value). In

our study we use the modified Epidemic Type Aftershock Sequence model (ETAS),

which allows to treat the first and the second generations of aftershocks separately. We

find that K and α parameters seem to be correlated with a postseismic slip; and the

primary aftershock density depends on the value of the coseismic slip.

34

Spatio-temporal renewal model for repeating earthquakes and analysis

of slip rate on the upper surface of the subducting Pacific Plate

Shunichi Nomura, Naoki Uchida, Yosihiko Ogata

We propose a new spatio-temporal stochastic model based on a renewal process and

analyze repeating earthquakes on the upper surface of the subducting Pacific Plate to

estimate spatio-temporal transition of slip rate on the plate boundary.

A renewal process is a point process that assumes intervals of events are independently

and identically distributed. It is applied to long-term forecast of large earthquakes in

active faults or on plate boundaries. But when we apply it to small repeating earthquakes,

the assumption of stationarity in renewal processes often fails because their intervals are

influenced largely by the change in slip rate near their hypocenters. Thus, we consider a

non-stationary renewal process that the repeating intervals are inversely proportional to

their neighbourhood slip rate. We represent the transition of slip rate by continuous

spatiotemporal function to cover overall observed area. To avoid over-fitting of the

estimated function, we apply penalties for unsmooth change in this function. Optimal

weights in the penalties are selected by Akaike’s Bayesian Infromation Criteria (ABIC).

We use relation between magnitudes and slip size derived by Nadeau and Johnson (1998)

to estimate the absolute slip rate from repeating earthquakes.

We analyzed repeating earthquake catalogue on subduction zone of Pacific Plate and

estimate slip rate history of plate boundary. We see the characteristic changes in slip rate

before and after the major earthquakes such as Sanriku-Haruka-Oki (1994 M7.6),

Tokachi-Oki (2003 M8.0), Kushiro-Oki (2004 M7.5), Fukushima-Oki (2008 M6.9),

Ibaraki-Oki (2008 M7.0) and large foreshocks of Tohoku-Oki (2011 M9.0). Proposal

model can estimate slip rate at depth where GPS system cannot measure directly.

Although it is difficult to estimate coseismic slip of large earthquakes from repeating

earthquakes, this model may be useful to monitor the transition of stress field or interplate

coupling on plate boundaries.

35

Kostrov method applied to repeating multiplets


(Institute of Geophysics, China Earthquake Administration, 100081 Beijing)

Kostrov method, the summation of seismic moment tensor elements for a specified area,

is one of the methods to map the average slip rate in deep, albeit suffers from the large

area average. In recent years, ‘repeating earthquakes’ identified by waveform cross

correlation have provide an opportunity to explore the average slip rate within a

‘repeating multiplet’. This average is still not the slip rate measured by strictly defined

‘repeating multiplets’, but can be regarded as an improvement of the traditional Kostrov

method due to the limited size of the ’multiplet’ and the similarity of the focal

mechanisms of the ‘repeating events’. We show two cases of such analysis. One case is

related to the November 29, 1999, Xiuyan, Liaoning, China, MS5.4 earthquake. The

‘repeating events’ are identified using the seismic waveform data from the Liaoning

Regional Seismograph Network, spanning the time before and after the Xiuyan

earthquake. The ‘multiplet’ is defined by the senso lato criterion that each event has at

least one partner in the ‘multiplet’. Two ‘multiplets’, located near the seismogenic faults

of the 1999 Xiuyan earthquake and the February 4, 1975, Haicheng MS7.3 earthquake,

respectively, show different behavior. For the ‘multiplet’ spanning before and after the

1999 Xiuyan earthquake, apparent pre-shock accelerating-like slip behavior, clear

immediate-post-seismic change, and relaxation-like post-seismic change can be observed.

As a comparison, for the ‘multiplet’ near the 1975 Haicheng earthquake which occurred a

quarter century ago, the cumulative slip appears linear, with a much smaller slip rate. The

other case is the ‘repeating events’ among the aftershocks of the 2008 Wenchuan

earthquake centered at the Wenchuan-earthquake Fault Scientific Drilling (WFSD) Site

#1 during and after the drilling process, by waveform cross correlation of three

component seismic waveforms. Using 12 ‘repeating multiplets’, defined by the senso

stricto criterion that each pair of events in the ‘multiplet’ must be ‘repeating pairs’, fault

slip rates are estimated. Slip rate was averaged as about 5mm/yr, being within the range

of the deformation rate before the Wenchuan earthquake obtained by strictly defined

‘repeating multiplets’, with a weak attenuating trend, and a suspected disturbance from a

strong aftershock.

36

Mechanism of spontaneous and triggered shallow creep events -

Implications for shallow fault zone properties

Meng Wei, Yoshihiro Kaneko, Yajing Liu, Jeffrey J. McGuire

Slip on tectonic faults take place over a wide range of spatial and temporal scales as

earthquakes, continuous aseismic creep, or transient creep events. Shallow creep events

on continental strike-slip faults can occur spontaneously, or are coupled with earthquake

afterslip, or are triggered by nearby earthquakes. Despite more than five decades of

observations, the mechanism of shallow creep events and their implications for seismic

hazard are still not fully understood.

To understand the mechanism of creep events, we developed a physics-based numerical

model to simulate shallow creep events on a strike-slip fault with rate-and-state frictional

properties. We show that the widely used synoptic model (Scholz, 1998) cannot

reproduce both rapid afterslip and frequent creep events, as observed on the Superstition

Hills fault (SHF) in the Salton Trough, southern California (USA), after the 1987 Mw 6.6

earthquake. Rather, an unstable layer embedded in the shallow stable zone is required to

match the geodetic observations of the creep behavior (Wei et al. 2013).

Using the strike-slip fault model, we also study the triggering process of creep events, by

either static or dynamic, or combined stress perturbations induced on the fault by a

nearby earthquake. Preliminary results show that static stress perturbations in the

effective normal stress can advance or delay creep events. The magnitude and timing of

perturbations determine the clock change of creep events. Dynamic stress perturbations in

effective normal stress can advance the timings of creep events when the perturbation

temporally decreases the effective normal stress. Perturbations that temporally increase

effective normal stress do not have significant influence on the timings of future creep

events.

By developing state-of-the-art models and constraining parameters with geodetic datasets

from continental faults (e.g., SHF in southern California, Xianshuihe Fault in

southwestern China), we aim to transition from a conceptual understanding of fault creep

towards a quantitative and predictive understanding of the physical mechanism of creep

events.

37

Statistical properties of low-frequency earthquakes triggered by large

earthquakes in southern Taiwan

Chi-Chia Tang1*, Zhigang Peng2, Cheng-Horng Lin1, Kevin Chao2, 3, and Chau-Huei

Chen4

1. Institute of Earth Sciences, Academia Sinica, 128, Sec. 2, Academia Rd., Nangang,

Taipei 11529, Taiwan 2. School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 311

Ferst Drive, Atlanta, Georgia 30332, U.S.A. 3. Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo

113-0032, Japan 4. Department of Earth and Environmental Science, National Chung Cheng University,

168 University Rd., Min-Hsiung, Chia-Yi County 62102, Taiwan

The recent findings of widespread triggered tremors (TTs) and low-frequency

earthquakes (LFEs) in various tectonic environments provide a way to study the

fundamental properties of deep tectonic tremor. Here we quantify the relationship

between TTs and LFEs beneath the Central Range in Southern Taiwan and their

statistical properties during the teleseismic waves of six large distant earthquakes. By

using waveforms of 11 LFEs triggered by the 2005 Mw 8.6 Nias earthquake as templates,

we scan through 12-hours of waveform data around the 6 mainshocks and identify a total

of 783 LFEs. Most of LFEs occurred within TT during the passage of large-amplitude

surface waves, and the increase of the LFE rate is statistically significant. The LFE rates

do not follow an Omori’s type decay, but abruptly return to the background rate

immediately after the surface-wave passage. These findings suggest that LFEs do not

trigger each other, but are driving by an external forcing. The LFEs were mainly located

in a compacted region between 12 and 36 km in depth near the Chaochou-Lishan Fault.

We infer that TTs consist of many reoccurring LFEs and the TT sources are persistent

over time.

39

August 13th, 2013, Tuesday

Morning

Session 2: Development of models and methods

8:30 - 8:50 Estimating the statistical models of earthquake occurrences

from the data of incompletely detected earthquakes

Takahiro Omi, Yosihiko Ogata, Yoshito Hirata and

Kazuyuki Aihara

8:50 - 9:10 Further investigations into the ETAS model

David Harte

9:10 - 9:30 On the stress release models with new tips from geophysics:

Bayesian estimation, forecasting and validation


9:30 - 10:00 (I) A Bayesian approach to estimate the periodic change in

earthquake detection capability and its applications to JMA

catalogue

Takaki Iwata


Session 3: Earthquake predictability, precursors and tests

10:20 - 10:50 (I) Real-time foreshock discrimination

Yosihiko Ogata

10:50 – 11:10 The spatio-temporal evolution of seismic activity preceding

and following the 5 September 2012 Nicoya Peninsula

earthquake

Jacob Walter, Zhigang Peng, Xiaofeng Meng, Susan Y.

Schwartz, Andrew V. Newman, and Marino Protti

11:10 - 11:30 Test seismicity anomalies by using the ETAS model as null

hypothesis

Jiancang Zhuang

40

11:30- 11:50 Assessing the potential improvement in short-term

earthquake forecasts from incorporation of GPS data

Ting Wang, Jiancang Zhuang, Teruyuki Kato, and Mark

Bebbington

11:50 - 12:20 (I) Temporal and spatial anomalies of seismo-ionospheric

anomalies in the total electron content associated with large

earthquakes

J. Y. Liu, Y. C. Su, C. H. Chen, H. F. Tsai, and Y. I. Chen

41

Estimating the statistical models of earthquake occurrences from the

data of incompletely detected earthquakes

Takahiro Omi, Yosihiko Ogata, Yoshito Hirata, and Kazuyuki Aihara

It is well known that a significant portion of triggered earthquakes immediately after a

strong earthquake are missing from hypocenter catalogs. This is because the overlapping

seismic waves of the intensively successive events make it difficult to discriminate each

individual event. Such deficiency of the data may provide biased results in seismicity

analysis. In this presentation, we first develop a state-space model for estimating the

time-dependent detection rates of earthquakes in order to model the statistical feature of

deficiency of the observed data. Then we fit the statistical models of earthquake

occurrences (e.g., the Omori-Utsu formula of the aftershock decay or the ETAS model)

by considering the detection rates. We present the applications of our method to the

forecasting of seismicity.

42

Further investigations into the ETAS model

David Harte

We present further investigations, that follow on from Harte (2013, GJI 192(1)), on the

ETAS model. Firstly, we investigate the effect of non-isotropic aftershock spatial

distributions based on fault strike angles derived from the moment tensor solutions.

Secondly, a problem identified in Harte (2013) was that most major sequences were

being under-fitted, while those space-time regions exhibiting "normal" seismicity were

being over-fitted. This could indicate that aftershock generation (offspring) by a parent

event of a given magnitude tends to be greater during a major sequence than during

"normal" seismicity. A modification to the model that partially fixes this problem is to

add an interaction term, between historical events, to the conditional intensity function.

This is done in such a way that if two historical events are close to each other and also

close to the space-time point being evaluated, then this interaction term will be much

greater than if one of the three points is not close to the others. Such an interaction term is

consistent with an assumption that the effect of each historical event is not necessarily

independent of other historical events, and those occurring close to each other further

raise the intensity function above that level expected when each historical event acts

independently.

43

On the stress release models with new tips from geophysics: Bayesian

estimation, forecasting and validation


The stress release model belongs to the class of self-correcting point processes of Isham

and Westcott (1979) with history-conditioned intensities. Based on the elastic-rebound

theory formulated by Reid in 1906, it is still the most feasible physical description of the

long-term evolution of the earthquake process.

Let us consider a region that can be regarded as a seismic unit on the basis, for instance,

of the kinematic context and the expected rupture mechanism. “Stress” generically

indicates the quantity X which governs the state of the system in that region and it is

assumed to increase linearly with time at a constant loading rate c imposed by external

tectonic forces until it exceeds the strength of the medium; X then decreases abruptly

each time an earthquake occurs. Stochastic models that meet this hypothesis can be

thought in terms of stress budget between the expected and observed values of stress X,

with the implication that a forthcoming seismic event is more likely to occur when the

observed stress is lower than the expected. Among these there is the stress release model.

We focus on the concept of stress X: it can be any physical parameter constituting a proxy

measure of the strength of an earthquake with the only constraint that, when dealing with

long-term seismic hazard, this physical quantity can be evaluated from historical events.

In the two classical versions of the stress release model, the stress X is the Benioff strain

and the seismic moment, respectively.

In some recent geophysical studies by Senatorski (2006, 2007) and by Kanamori and

Heaton (2000), seismic energy and scaled energy are proposed as quantitative measures

of the size and strength of an earthquake. Hence we consider two new versions of the

stress release model in which these quantities represent the stress X, respectively. Since

both seismic energy and scaled energy are expressed also through the rupture area of the

earthquake, we approximate the rupture area by the Wells and Coppersmith regression for

the faulting type. Bayesian estimation, forecasting and validation of the four stress release

models, respectively driven by seismic strain, moment, energy and scaled energy, are

carried out applying the models to Italian historical seismicity.

44

By exploiting DISS database and CPTI04, CPTI11 catalogs, we subdivide the Italian

territory into eight tectonically-coherent large regions and then associate the seismic

history of each composite source to its region, thereby obtaining eight regional data sets.

Bayesian analysis of all the proposed models for each data set is carried out so that the

posterior distributions of the model parameters provide both the parameter estimates and

measures of their uncertainty.

The forecasting problem is formulated in terms of probability distribution of the time t to

the next event conditioned on the history of the process up to t in the region. We find that

the time to the next event has the Gompertz distribution, a well-known extreme value

distribution, with shape and scale parameters depending on the model parameters and, in

particular, the shape parameter depending on the value of the conditional intensity

function at time t. Results of retrospective and prospective validations are obtained by

comparing the expected and observed occurrence times of the events in the datasets and

in the time period from the end of the catalog, 2003, to present time, 2012. In this time

period there have been four earthquakes exceeding the magnitude threshold 5.3,

excluding aftershocks: the largest ones are the L’Aquila earthquake, Mw 6.3, of April 6,

2009, and the Finale Emilia earthquake, Mw 5.9, of May 20, 2012. Both events fall

between the estimated median and mean of the corresponding time to the next event.

References

- Isham, V., and M. Westcott (1979) A self-correcting point process, Stochastic Processes

and Their Applications, 8, 335-347.

- Kanamori, H and Heaton, TH (2000) Microscopic and macroscopic physics of

earthquakes, Geocomplexity and the Physics of Earthquakes, Geophysical Monograph 20,

AGU, 127-141. - Senatorski, P (2006) Fluctuations, trends and scaling of the energy

radiated by heterogeneous seismic sources, Geophys. J. Int., 166, 267-276.

- Senatorski, P. (2007) Apparent stress scaling and statistical trends, Physics of the Earth

and Planetary Interiors, 160, 230-244.

45

A Bayesian approach to estimate the periodic change in earthquake

detection capability and its applications to JMA catalogue

Takaki Iwata

In earthquake forecasting, evaluating completeness of an earthquake catalogue is one of

the key issues. Conventionally the completeness magnitude (Mc), the minimum

magnitude of complete recording, is estimated for an earthquake catalogue ranging over

several weeks, months or years with the assumption of being invariant in time. However,

the earthquake detection capability and Mc is variable. For instance, owing to human

activity, the detection capability has been shown to be lower in daytime than nighttime.

This study presents evaluation of the detection capability and Mc in which we consider

such daily variation. For quantitative evaluation of the detection capability, the model

representing a magnitude-frequency distribution of earthquakes covering the entire

magnitude range [Ogata & Katsura, 1993, GJI] was introduced. Then, the temporal

variation in the model parameter, which corresponds to the quality of the earthquake

detection capability, was estimated by adopting a Bayesian approach with a piecewise

linear approximation. This method was applied to the recent Japan Meteorological

Agency (JMA) catalogue, and the results shows that the estimated values of Mc were

around 2.5 or 3.0; these values are more conservative than the magnitude threshold

suggested by earlier studies [e.g., Nanjo et al., 2010, BSSA].

Another application example is the decomposition of seasonality and long-term trend in

earthquake detection capability. Because of the seasonality of climatic factors such as

temperature and wind [e.g., Hillers & Ben-Zion, 2011, GJI] noise amplitudes observed at

seismic stations sometimes show evidence of annual variations, which may cause the

seasonal variation in the detection capability. A similar Bayesian framework as described

above was applied to the JMA datasets in and around the northern Honshu island, Japan,

and we successfully extracted the seasonality of the detection capability that is related to

the annual variation of the wind speed and a long-term trend corresponding to the recent

improvement of the seismic network in the examined region.

46

Real-time foreshock discrimination

Yosihiko Ogata

Institute of Industrial Science, University of Tokyo, and

The Institute of Statistical Mathematics, Japan

We are concerned with real-time forecasting of the probability that current earthquakes

are “foreshocks” of a forthcoming significantly larger earthquake. Specifically,

foreshocks are defined as the earthquakes in a cluster preceding the largest earthquake

that is larger by a magnitude gap of 0.5 or more[1]; otherwise, they are defined as

“swarm”. When a series of earthquakes occurs in a region, we attempt to statistically

discriminate foreshocks from a swarm or mainshock-aftershock sequence. After real time

identification of an earthquake cluster using the single-link algorithm, the probability is

calculated based on the statistical features that discriminate foreshocks from the other

types of clusters, such as the earthquakes' stronger proximity in time and space in

addition to the tendency towards chronologically increasing magnitudes. These features

were modeled for probability forecasting and the coefficients of the model were

estimated for the JMA hypocenter data (M≧4, 1926-1993) [1].

Currently 20 years has passed since the publication of the above stated work so that we [2]

present the performance and validation of the forecasts (1994-2011) by using the same

model. This forecasting performs significantly better than the unconditional (average)

foreshock probability throughout Japan region. The frequency ratios of the actual

foreshocks to remaining type of earthquakes are consistent with the forecasted

probabilities.

Furthermore, I would like to discuss universality of the discriminating features, and also

to present an extension to forecasting of earthquake magnitude.

Reference:

[1] Ogata, Y., Utsu, T. and Katsura, K. (1996). Statistical discrimination of foreshocks

from other earthquake clusters, Geophys. J. Int. 127, 17-30.

[2] Ogata, Y. and Katsura, K. (2012). Prospective foreshock forecast experiment during

the last 17 years, Geophys. J. Int., 191, 1237-1244.

47

The spatio-temporal evolution of seismic activity preceeding and

following the 5 Septemper 2012 Nicoya Peninsula earthquake

Jacob Walter, Zhigang Peng, Xiaofeng Meng, Susan Y. Schwartz, Andrew V. Newman,

and Marino Protti

The subduction megathrust interface, at the Nicoya Peninsula, exhibits a wide range of

complex fault behavior, from recently discovered slow slip and tremor, numerous

microearthquakes, to infrequent megathrust (>Mw7) earthquakes. Over the last 10 years,

an NSF-funded international and multi-University network of GPS stations and

seismometers has detected at least 5 slow slip events accompanied with increased tremor

activity. In contrast to other subduction zones, the tremor originates up-dip, down-dip,

and within the seismogenic zone. On September 5, 2012, an Mw 7.6 earthquake occurred

directly beneath this network, making the Nicoya Peninsula uniquely poised to

investigate the wide range of fault behavior and spatio-temporal evolution of seismic

activity around the mainshock. Preliminary matched-filter analysis using a template

earthquake that precedes the mainshock by ~120 s indicates similar events occurring 20 -

40 min prior to the mainshock, as well as, immediately following the mainshock. We are

currently expanding this analysis with a broader catalogue of template events and

utilizing matched-filter codes optimized for graphics processing units (GPUs). The early

aftershocks cluster in a distinct region that is immediately adjacent to regions that have

undergone slow slip in past events. By systematically detecting all possible seismic

events around the mainshock, we hope to gain better insight into the spatio-temporal

transitions from stable sliding to stick-slip motion, and underlying physics of earthquake

nucleation and interaction.

48

Test seismicity anomalies by using the ETAS model as null hypothesis

Jiancang Zhuang

Many methods have been developed for earthquake prediction, including Pattern

Informatics (PI), M8, RTP (Reverse Tracing of Precursors), RTL (region-time-length),

AMR (Accelerating Moment Release) and etc. In these methods, some seismicity

indexing functions are developed and calculated from the history of the earthquake

occurrences. If these indexing functions depart from their normal levels, alarm will be

given for the occurrence of a large earthquake in the future. However, these prediction

methods detect anomalies based on the null hypothesis that the seismicity, or at least the

seismicity of major earthquakes, obeys the Poisson model. It is known that the seismicity

is clustered. Because earthquake clusters destroy this assumption, declustering is always

applied to the earthquake catalog as a pre-processing step before applying these methods.

On the other hand, it is widely accepted that standard earthquake clusters can be

described by the Epidemic Type Aftershock (ETAS) model. Using the residual analysis

theory developed by Zhuang (2006, JRSSB), this study revises the above earthquake

prediction methods into versions that extract useful precursory information based on a

standard earthquake clustering model (the ETAS model) as null hypothesis.

49

Assessing the potential improvement in short-term earthquake forecasts

from incorporation of GPS data

Ting Wang, Jiancang Zhuang, Teruyuki Kato, and Mark Bebbington

This study validates the idea that changes of ground deformation recorded by GPS

contain useful information for earthquake forecasting. A filtering technique called

moving rate of variation (MRV) is used to extract short-term signals from the time series

of GPS records of deformation from the North Island of New Zealand, Southern

California and the Kanto Region of Japan. The short-term precursory information of these

GPS signals for large earthquakes is evaluated using Molchan's error diagram. The results

suggest that the GPS signals extracted in this study do contain precursory information for

predicting large earthquakes, with a probability gain of 2 ~ 4 against a Poisson model.

Two further tests are conducted to eliminate the possibility that the precursory

information in the GPS signals is due to their occurrence after large earthquakes and

before later large aftershocks. Swapping the roles of GPS signals and earthquakes in the

Molchan error diagram, the first test shows that the GPS signals are not triggered by large

earthquakes. Using earthquakes as both signal and targets in the Molchan error diagram,

the second test shows that the selected catalogs in this study are not clustered. These

results imply that precursory information in the GPS data can be used to augment

probabilistic models based on seismic catalog data, in order to improve forecasting of

large earthquakes.

50

Temporal and spatial anomalies of seismo-ionospheric anomalies in the

total electron content associated with large earthquakes

J. Y. Liu and Y. C. Su at Institute of Space Science, National Central University, TAIWAN;

C. H. Chen at Department of Earth Science, National Cheng Kung University, TAIWAN; H.

F. Tsai GPS Science and Application Research Center, National Central University,

TAIWAN

Y. I. Chen at Institute of Statistics, National Central University, TAIWAN

This paper applies statistical analyses to examine temporal and spatial anomalies of the

total electron content (TEC) in global ionosphere map (GIM) associated with the 1999

Chi-Chi M7.6 earthquake, 2004 Sumatra M9.3earthquake, 2008 Wenchuan M8.0

earthquake, 2010 Haiti M7.0 earthquake, and 2011 Tohoku M9.0 earthquake. To detect

temporal anomalies, based on previous 15-day data a quartile-based (i.e. median-based)

process is performed. Based on the persistence, the spatial analysis is further conducted to

discriminate global effects, such as magnetic storms, and local effects, such as earthquake

to find whether the observed anomalies being possibly associated with the followed

earthquake or not. Ionospheric models are also employed to simulate the anomalies

appearing before the 2008 Wenchuan M8.0 earthquake and 2011 Tohoku M9.0

earthquake. Results show that the electric potentials and/or electric fields appearing

around the epicenter area during the earthquake preparation period play an important role.

51

August 13th, 2013, Tuesday

Afternoon

Session 3 (Cont.) Earthquake predictability, precursors and tests

14:00 - 14:20 Statistical analysis of microwave remote sensing data for

earthquake related thermal anomaly over the India-China

border region


14:20 - 14:50 (I) An ensemble seismic hazard model for Canterbury, New

Zealand

Matt Gerstenberger

14:50 - 15:20 (I) Japanese earthquake predictability experiment with

multiple runs before and after the 2011 Tohoku-oki

earthquake

Naoshi HIRATA, Hiroshi TSURUOKA, Sayoko YOKOI

15:20 - 15:50 (I) A hybrid statistical/physical model for forecasting

aftershock rates

Sandy Steacy, Matt Gerstenberger, Charles Williams,

David Rhoades, and Annemarie Christophersen

15:50 - 16:20 Coffee break and visiting posters

Session 4 Special session on the Lushan earthquake

16:20 - 16:40 Challenges of statistical seismology from the Lushan

earthquake

Zhongliang Wu and Changsheng Jiang

16:40 - 17:00 Is the 2013 Lushan Ms 7.0 earthquake an aftershock of the

2008 Wenchuan Ms 8.0 earthquake on Longmen Shan fault,

Sichuan, China?

Ke Jia, Shiyong Zhou, Jiancang Zhuang, and Changsheng

Jiang

52

17:00 - 17:20 Discussion of the predictability of Lushan M7.0 earthquake

by Pattern Informatics method

Yongxian Zhang and Xiaotao Zhang.

17:20 - 18:00 Panel discussion

The April 20, 2013, Lushan Ms7.0/Mw6.8 earthquake and the

seismicity gap in the Southern Longmenshan fault zone

(Materials and scope please see Home Page)

Panelists: Shiyong Zhou, Zhang Yongxian, David D. Jackson,

Zhongliang Wu


53

Statistical analysis of microwave remote sensing data for earthquake

related thermal anomaly over the India-China border region


Analysis of microwave remote sensing data of MODIS satellite have been used for

investigation of thermal anomaly in and around the earthquakes epicentres. Here we

examine one year daily (day-night) data of Land Surface Temperature (LST) and

emissivity, extracted from 1 km resolution for four events. Temporal and spatial coverage

can exhibit thermal variations over the epicentral region. Statistical analysis of the

microwave remote sensing data shows some significant precursors of earthquake. It is

found that LST anomaly is observed well before the earthquakes which show in increase

emissivity between band 31 and 32 data of MODIS satellite. In this study microwave

remote sensing technique may provide possible explanation about the well-known

phenomena of earthquake related thermal anomaly and can be read as earthquake

precursors.

54

An ensemble seismic hazard model for Canterbury, New Zealand

Matt Gerstenberger

We present updates of the time-dependent hazard modelling for the Canterbury plains

region following the recent Canterbury earthquakes, and the subsequent updates of the

NZS1170.5 (2004) earthquake design standards for Christchurch. Seismicity in the region

continues to be very high relative to activity prior to the September 2010 earthquake,

requiring development of earthquake hazard estimates that model time-varying seismicity

rates. We have developed and applied an ensemble model that covers short-term,

medium-term and long-term expected earthquake rates. With model weights that were

subjectively defined using a structured expert elicitation process, we have combined the

following models: STEP, ETAS, EEPAS00, EEPAS01, PPE, and NSHMBG,

NSHMBG50. The increase in expected rates for Christchurch from prior to 2010 has

resulted in roughly a 75% increase in the building design standard. All models were

previously installed in the NZ CSEP testing centre. Since model implementation we have

run a series of retrospective tests of the ensemble model, and it is currently being tested in

real time within the testing centre.

55

Japanese earthquake predictability experiment with multiple runs

before and after the 2011 Tohoku-oki earthquake

Naoshi Hirata, Hiroshi Tsuruoka, and Sayoko Yokoi

The current Japanese national earthquake prediction program emphasizes the importance

of modeling as well as monitoring for a sound scientific development of earthquake

prediction research. One major focus of the current program is to move toward creating

testable earthquake forecast models. For this purpose, in 2009 we joined the

Collaboratory for the Study of Earthquake Predictability (CSEP) and installed, through an

international collaboration, the CSEP Testing Centre, an infrastructure to encourage

researchers to develop testable models for Japan.

The experiment consists of 12 categories, with 4 testing classes with different time spans

(1 day, 3 months, 1 year and 3 years) and 3 testing regions called “All Japan,”

“Mainland,” and “Kanto.” A total of 160 models, as of May 2013, were submitted, and

are currently under the CSEP official suite of tests for evaluating the performance of

forecasts.

We will discuss results of prospective forecast and testing for periods before and after the

2011 Tohoku-oki earthquake. Because a seismic activity has changed dramatically since

the 2011 event, performances of models have been affected very much. Also, we will

discuss the retrospective earthquake forecast experiments for aftershocks of the 2011

Tohoku-oki earthquake. Our aim is to describe what has turned out to be the first

occasion for setting up a research environment for rigorous earthquake forecasting in

Japan.

56

A hybrid statistical/physical model for forecasting aftershock rates

Sandy Steacy, Matt Gerstenberger, Charles Williams, David Rhoades, and Annemarie

Christophersen

At present, there are two main methods for estimating aftershock rates - a physics based

approach generally based on Coulomb stress changes combined with rate-state friction, or

purely statistical techniques using ETAS or STEP models. The problem with the latter is

that they leave out the stress interaction that appears to control much of the spatial

distribution of aftershocks, whereas the former depend strongly on knowing the details of

the slip distribution in order to accurately calculate the magnitude of the stress change.

Here we develop a new model that combines the spatial constraints from Coulomb stress

calculations with the statistical approach of STEP. In essence, we use the Coulomb

“map” as a Boolean filter and increase the likelihood of aftershocks in regions of positive

Coulomb stress and decrease it in areas of negative stress. We do not consider the

magnitude of the Coulomb stress change in this filter, but simply whether the stress

change is positive or negative.

We apply 2 variations of this model to the Canterbury earthquake sequence, one in which

we apply the STEP model within 5 km of the fault zone and solely use the Coulomb filter

for off-fault aftershocks and another in which the filter is applied everywhere. We test

these against the STEP model on its own and against an implementation of Coulomb

rate-state both retrospectively and pseudo-prospectively. We find that retrospectively the

hybrid model performs better than STEP for 2 events and about the same for the other 2

while pseudo prospectively it performs better for one, similarly for 2 others, and worse

for the first event in the sequence. The Coulomb rate-state approach performs worst in all

tests. Our results suggest that incorporating the physical constraints from Coulomb stress

changes can improve the power of statistical models and clearly show the importance of

good data quality for prospective forecasting.

57

Challenges of Statistical Seismology from the Lushan earthquake

Zhongliang Wu and Changsheng Jiancang

The April 20, 2013, Lushan, Sichuan Province, China. MW6.8/MS7.0 earthquake raises several

practical questions of social concern to statistical seismology. 1) The role of the ‘hidden’ earthquakes,

which had no surface faulting trace and thus disappeared from the historical earthquake lists due to

the lack of human records, in the long-term estimate of seismic hazard; 2) The property and future

trend of the ‘seismic gap’ between the Lushan earthquake and the rupture zone of the Wenchuan

earthquake; 3) The property and future trend of the ‘seismic gap’ between the Lushan earthquake

and the ‘triple-junction’ part of the Xianshuihe-Anninghe-Longmenshan faults; 4) The seismic

tendency of the Xianshuihe fault, and the relation between the Xianshuihe fault and the

Longmenshan fault zone; and 5) The property of the Lushan aftershock sequence and the probability

of strong aftershock/s. This introductory presentation, facing to the above mentioned questions,

provides the Special Session with background information of the Lushan earthquake and the

follow-up studies, as well as the on-going field investigation.

58

Is the 2013 Lushan Ms 7.0 earthquake an aftershock of the 2008

Wenchuan Ms 8.0 earthquake on Longmen Shan fault, Sichuan, China?

Ke Jia, Shiyong Zhou, Jiancang Zhuang and Changsheng Jiang

The relationship between the Lushan Ms 7.0 earthquake, which occurred on 20 April

2013, and the 2008 Wenchuan Ms 8.0 earthquake is still under debate. One view is that

the Lushan earthquake is the strongest aftershock of the Wenchuan earthquake and the

converse opinion believes that the Lushan earthquake is an independent event. To clean

up this debate, we use the ETAS (Epidemic-type aftershock sequence) model and the

stochastic declustering method to obtain the background or independent probabilities of

the Lushan earthquake. The results show that, besides triggered aftershocks in its source

fault, the Wenchuan earthquake also changed the background seismicity rate in the

Lushan region, about 1.3 as the original rate. The proportion of contributions to the

occurrence of the Lushan earthquake from the aftershock effect (in the sense of the ETAS

model), the increment of the background seismicity, and the original background

seismicity are, respectively, 12%, 50% and 38%. Considering the relaxation of the lower

crust and upper mantle, the combined (coseismic plus postseismic viscoelastic) Coulomb

failure stress (CFS) changes on the initial rupture point of the Lushan earthquake are

brought 0.1~0.4 bar closer to failure. Thus, we propose the occurrence of the Lushan

earthquake was dramatically affected by the Wenchuan earthquake.

59

Discussion of the predictability of Lushan M7.0 earthquake by Pattern

Informatics method

Yongxian Zhang and Xiaotao Zhang

The Pattern Informatics (PI) method is a new approach to earthquake forecast based on

statistical physics. Through strict mathematical statistics, this method could detect the

regions where the seismicity significantly deviates from the normal state (i.e., seismic

quiescence or seismic activation), known as “seismic hotspots”. Previous research results

show that PI is an earthquake forecast model for medium to long-term earthquake

forecast with high efficiency. In this paper, PI model was applied to Sichuan-Yunnan and

its adjacent region for detecting seismic hotspots before Lushan M7.0 earthquake on Aril

20, 2013. Based on the aftershock removal earthquake catalogue since 1970 from China

Earthquake Networks Center, and suitable calculating parameters (with grid size of 2°×2°

and forecast window of 9 years) with higher forecast efficiency according to the previous

research work on West China, the evolution of PI anomaly during the time after

Wenchuan M8.0 earthquake and before Sichuan Lushan M7.0 earthquake in

Sichuan-Yunnan region was obtained. The results show that obvious seismic hotspots

appeared in the convergent region （29-31°N，101-105°E）of Xianshuihe,

Longmenshan and An'ninghe faults from 2009 to 2010. The seismic hotspots shrank to

the range of (29-31°N，101-103°E) during the years of 2011-2012 and disappeared

after 2012. The Lushan M7.0 earthquake dropped in the hotspots in 2013. Evolution of PI

anomaly with another set of calculation parameters (with grid size of 1°×1° and forecast

window of 9 years) also showed that there was hotspot (29-30°N, 103-104°E) from 2009

to 2010 covering the southern Xinjin-Chengdu-Deyang fault, southern Longquanshan

fault, Mabian-Yanjin fault, Ebian fault and Tianquan-Yingjing fault. After 2011, the

hotspot disappeared and the Lushan M7.0 earthquake occurred in 2013. The influence of

calculation parameters to the predictability of PI method was discussed in this paper, and

the potential seismic risk in this region was also discussed.

60


61

August 14th, 2013, Wednesday

Morning

Session 5 Estimating maximum magnitude

9:00 - 9:30 (I) Magnitude limits of subduction zone earthquakes


9:30 - 10:00 (I) Common problems in estimation of seismic hazard source

parameters and their solution

Andrzej Kijko

10:00 - 10:40 Coffee break and visiting posters

10:40 - 11:10 (I) New Multiple Dimension Stress Release Statistic Model

based on co-seismic stress triggering


11:10 - 11:40 (I) What can be learned from earthquake catalogs about the

largest expected magnitudes?

Gert Zöller, Matthias Holschneider, Sebastian Hainzl,

Jiancang Zhuang

11:40 - 12:20 Discussion

62


63

Magnitude limits of subduction zone earthquakes


Maximum earthquake magnitude (mx) is a critical parameter used in seismic hazard and

risk analysis. The choice of mx may significantly affect the seismic hazard and risk

results, on which public policy and business decisions are made. The 2011 magnitude 9.0

Tohoku, Japan, earthquake surprised many geoscientists because most of the prior

estimates of the maximum magnitude (mx) for that area were below 8.5. The devastating

2004 magnitude 9.1 Sumatra, Indonesia, earthquake was also unexpected by many

geoscientists.

To avoid underestimating mx from the incomplete historical earthquake record, we

introduce a new concept: probable maximum magnitude expected in T years, mp(T). This

concept relates maximum magnitude with a time scale. To estimate mp(T) for each of the

circum-Pacific subduction zones, we employ a Tapered Gutenberg-Richter (TGR)

magnitude distribution to project the rate of great earthquakes from the rate of small

earthquakes. We start with a high-resolution smoothed global estimate of the rate of m ≥

5 earthquakes, known as the Whole Earth Model, from which we estimated the rate of m

≥ 5 quakes within each subduction zone. The TGR distribution has two parameters: the β

-value (the logarithmic slope of the distribution at small magnitudes), and the corner

magnitude mc (a parameter controlling the distribution in the upper range of magnitude).

We determine β and mc by maximum likelihood using the Global Centroid Moment

Tensor (GCMT) earthquake catalog and moment conservation principal. We use

Monte-Carlo simulation to estimate uncertainties. Our results show that most of the

circum-Pacific subduction zones can generate m ≥ 8.5 earthquakes over a 250-year

interval; over a 500-year interval, most of the zones can generate m ≥ 8.8 earthquakes;

and over a 10,000-year interval, m ≥ 9.0 earthquakes are expected along almost all of the

zones.

The Cascadia subduction zone stretches from northern Vancouver Island to Cape

Mendocino, California. Paleoseismic evidence indicates many great earthquakes during

the past 10,000 years, but it is currently seismically quiescent. We collate the 10,000-year

paleoearthquake data and thoroughly investigate the earthquake magnitude-frequency

distribution of the region by combining instrumental and paleoseismic data. Our results

show that over a 500-year period, m 8.8 and larger earthquakes are expected in this zone;

64

over a 1000-year period, m 9.0 and larger earthquakes are expected; and over a

10,000-year period, m 9.3 and larger earthquakes are expected.

65

Common problems in estimation of seismic hazard source parameters

and their solution

Andrzej Kijko

University of Pretoria, Natural Hazard Centre, Africa,

E-mail: [email protected]

Following the classic Cornell-McGuire probabilistic seismic hazard analysis procedure,

each seismic hazard source is characterised by at least three parameters: annual rate of

seismic activity , the b-value of the frequency-magnitude Gutenberg-Richter relation

and the upper limit of the earthquake magnitude mmax.

Assuming that successive earthquakes are independent in time, the number of

earthquakes with magnitude equal to or exceeding a certain level of completeness follows

the Poisson distribution with the parameter equal to the annual rate of seismic activity .

The maximum likelihood estimator of is then equal to n/t, where n is number of

events that occurred within time interval t. The maximum likelihood estiamation of the

b-value is equal to ),(/)(log min10 mme where m is the sample mean of earthquake

magnitude. The upper limit of earthquake magniude mmax, can be estimated in two

different ways, deterministic and probabilistic procedures.

The common problems in assessment of the above parameters are:

- incompleteness of seismic event catalogues

- uncertainty of earthquake magnitude determination

- application of not adequate models of spatial, temporal and size of earthquake

mode

distribution

The lecture will present how the above problems can be resolve.

Keywords: Seismic hazard source parameters, parameters estimation

66

New Multiple Dimension Stress Release Statistic Model based on

co-seismic stress triggering


Following the stress release model proposed by Vere-Jones (1978), we developed a new

multi-dimensional stress release model, which is a space-time-magnitude version based

on multi-dimensional point processes. First, we interpreted the exponential hazard

functional of the stress release model as the mathematical expression of static fatigue

failure caused by stress corrosion. Then, we reconstructed the stress release model in

multi-dimensions through incorporating four independent sub-models: the magnitude

distribution function, the space weighting function, the loading rate function, and the

co-seismic stress transfer model. Finally, we applied the new model to analyze the

historical earthquake catalogues in North China. An expanded catalogue, which contains

the information of origin time, epicenter, magnitude, strike, dip angle, rupture length,

rupture width and average dislocation, is composed for the new model. The estimated

model can simulate the variations of seismicity with space, time and magnitude.

Compared with the previous stress release models with the same data, the new model

yields much smaller values of AIC and AICc. The estimated model shows that 21

epicenters out of 37 are indicated as higher rates of earthquakes than the mean spatial

seismic rate just before the related earthquakes. The map of predicted earthquake rates at

the ending time (Jan. 1, 1997) suggests that the next destruct earthquake in North China is

likely to occur in the regions south of Datong, north of Beijing and east of Hejian.

67

What can be learned from earthquake catalogs about the largest

expected magnitudes?

Gert Zöller, Matthias Holschneider, Sebastian Hainzl, and Jiancang Zhuang

Earthquake catalogs are probably the most informative data source for the estimation of

various seismicity parameters. We discuss to which extent maximum magnitudes can be

estimated from earthquake catalogs. The absolute maximum magnitude cannot be

constrained from catalogs alone, independent of the details of the assumed model for the

magnitude distribution, e.g. whether a Gutenberg-Richter distribution is sharply truncated

or smoothly tapered for high magnitudes. In contrast, the maximum magnitude in a future

time horizon is a suitable quantity in this respect. We show, how this parameter can be

estimated from catalogs with various levels of quality. For one of the best available data

sets, the earthquake catalog of Japan, it is demonstrated that the size of the 2011 M9

Tohoku earthquake is not a surprise and that even larger earthquakes are possible.

Considering different parts of Japan, relatively low magnitudes are calculated in regions,

where the National Seismic Hazard Map shows high ground motion hazard.

69

Poster Session

Moment tensor inversion using exact calculated Green function in southeastern Iran


Probability of occurrence from characteristic earthquakes in the Corinth Gulf, Greece, fault

system

Maura Murru, Giuseppe Falcone, Rodolfo Console, Vassilis Karakostas,

Eleftheria Papadimitriou, David Rhoades


Giuseppe Falcone, Maura Murru, Rodolfo Console, Eleftheria Papadimitriou,

Vassilis Karakostas, David Rhoades


Abhey R. Bansal, Tsuruoka Hiroshi,

On the macroseismic attenuation from the probabilistic perspective. Applications in European

countries

Rotondi R., Varini E., Brambilla C.



Comparison of recent seismic hazard models based on the Gutenberg- Richter

magnitude-frequency relation


Numerical simulations of postseismic processes of the 1992 M7.2 Landers earthquake with a

damage rheology model

Lifeng Wang, Vladimir Lyakhovsky, Yariv Hamiel, Yehuda Ben-Zion and

Matthias Holschneider

Evaluation of annual, global seismicity forecasts, including ensemble models


Short-term foreshocks in Southern California and Italy as non-triggered events


A statistical study on seismo-ionospheric anomalies of the total electron content associated with

worldwide large earthquakes during 1998-2012

Y. I. Chen, J. Y. Liu, C. H. Chen, H. F. Tsai

Assessment of completeness and homogeneity of aftershock catalogue of 2001 MW 7.7 Bhuj

earthquake

S.K. Aggarwal, B.K. Rastogi, P.K. Khan, A.R. Bansal and S. Kumar

70


Xiaowei Chen, Aitaro Kato

Statistical study of ULF seismo-magnetic phenomena at Kakioka Observatory



Matt Gerstenberger, Jeremy Zechar, David Rhoades

Sensitivity of aftershock rates for a Wellington fault earthquake to different parameters.

Annemarie Christophersen, David Rhoades and Sebastian Hainzl.

Spatial variation of b-value and its tectonic implications



J.D. Zechar, J.L. Hardebeck, A.J. Michael, M. Naylor, S. Steacy, S. Wiemer1, and

J. Zhuang

71

Moment tensor inversion exact calculated Green function in

southeastern Iran


In Rigan region, southeast of Iranian plateau, two major earthquakes were occurred in 20

December 2010 and the 27 January 2011 with magnitudes of Mw=6.5 and Mw=6.2,

respectively. These earthquakes followed with more than 30 aftershocks with magnitude

greater than 3. These earthquakes were recorded by broadband stations of Iranian

National Seismic Network (INSN). These recorded earthquakes are used in this study to

explore the shear wave velocity structure using group velocity dispersion curves of the

fundamental mode of Rayleigh waves that are estimated by Frequency Time Analysis

(FTAN) method. To estimate the shear wave velocity structure, the average of estimated

dispersion curves is inverted using nonlinear inversion approach. This estimated shear

wave velocity structure was compared with other similar reported shear wave velocity

structures around southeast of Iranian plateau. In the next step, this shear wave velocity

structure is used to estimate Green function for exploring the reliable moment tensor of

the seismic source mechanism using the amplitude and phase spectra of the fundamental

mode of Rayleigh waves. Also an uncertainty analysis was performed to confirm the

reliability of the focal mechanism solutions. The consistency between the inverted focal

mechanisms and those obtained using the P-wave first motions was investigated.

Furthermore, to check the reliability of estimated shear wave velocity structure and

moment tensor, the synthetic seismograms were calculated for comparing with the

observed seismograms that they had good agreement to each other.

72

Probability of occurrence from characteristic earthquakes in the

Corinth Gulf, Greece, fault system

Maura Murru, Giuseppe Falcone, Rodolfo Console, Vassilis Karakostas, Eleftheria

Papadimitriou, and David Rhoades

The characteristic earthquake hypothesis modeled by the BPT or the Weibull

distributions has been tested on the Corinth Gulf, fault system. In our test the

time-independent uniform Poisson model is taken as the reference model. The

time-dependent hazard rate thus obtained is then modified by the inclusion of a

permanent physical effect due to the Coulomb static stress change caused by failure of

neighboring faults since the latest characteristic earthquake on the fault of interest. We

treat the uncertainties in the parameters of each examined fault source, such as linear

dimensions, depth of the fault center, focal mechanism, recurrence time, coseismic slip,

and aperiodicity of the statistical distribution, by a Monte Carlo technique. The Monte

Carlo samples for all these parameters are drawn from a uniform distribution within their

uncertainty limits. We aim to test if strong earthquakes on identified eight segments are

characterized by some kind of time-predictable behavior, rather than by complete

randomness. For a comparison among the results obtained from different models (Poisson,

BPT and Weibull), we also give the probabilities of occurrence for the next characteristic

earthquake, considering the 10th, 50th and 90th percentiles of the Monte Carlo

distribution, over the future 30 years, starting on 1 January 2013, considering the

information on used parameter uncertainties. The results of our statistical tests show a

slight superiority of the Weibull inter-event time distribution in comparison with the BPT

distribution. No clear performance enhancement is achieved by the introduction of the

Coulomb static stress change into the renewal model.

73


Giuseppe Falcone, Maura Murru, Rodolfo Console, Eleftheria Papadimitriou, Vassilis

Karakostas, and David Rhoades

We deal with the problem of retrospectively evaluating the validity of the two renewal

models, BPT and Weibull, and the same with stress transfer inclusion applied in the

Corinth Gulf, by comparing the forecasts with the historical information using the data of

the last 300 years. We evaluate the models, taking as reference model a plain

time-independent Poisson model, by means of statistical tools including the ROC

diagram, the R-score, the probability gain and the log-likelihood ratio. For each test were

calculated the 10th, 50th and 90th percentiles using the Monte Carlo procedure. We find

that the BPT and the Weibull renewal models yield comparable results, and both of them

perform significantly better than the Poisson hypothesis. No clear performance

enhancement is achieved by the introduction of the Coulomb static stress change into the

renewal model.

74


Abhey R. Bansal and Hiroshi Tsuruoka

We studied Gutenberg-Richter b-values variation with depth and space in the Kanto

region, Japan for a period from 2000 to 2012 using unified JMA catalogue. The events

are selected in different depth ranges at an interval of 20 km from 0 to 100 km. This

depth interval is selected based on the histogram of depth distribution in region to find

sufficient number of events. The completeness of magnitude (Mc) in the region varies

from 0.9 to 3.1 with lower and higher values for inland and offshore region, respectively.

The different trends of Mc are found for the different depth range. The higher range of

Mc is found for the depth interval for the shallow earthquakes of depths < 20 km with a

higher value of Mc corresponds to the area covering 33-35ºE and 138-140 ºN. This

estimated Mc is used for estimating the b-values in the region. Very low b-values are

found for the eastern portion of the region for all depth ranges. The b values decrease

with depth for < 60 km and then increase. We further divided the catalogue into two time

periods e.g. before and after 2011 Tohoku earthquake and same trend in b value is found

for all depth ranges. We also studied the depth distribution of triggered and background

events in the region and found that triggered events are generally lies at shallow depths.

75

On the macroseismic attenuation from the probabilistic perspective:

Applications in European countries

Rotondi R., Varini E., and Brambilla C.

In countries like Italy with long tradition in the compilation of historical seismic

databases the examination of macroseismic data can be useful in hazard assessment. In

this work we address the issue of the seismic attenuation from a probabilistic perspective

which enables to formalize both the aleatory variability and epistemic uncertainty

inherent the decay process. To this end the intensity Is at site, or analogously the intensity

decay ΔI, is considered as a random variable which follows a beta-binomial model, in

which Is has a binomial distribution over [0, I0] with parameter p(d), depending on the d

epicentre-site distance, that, in its turn, follows a beta distribution Be(α, β) (Zonno et al.,

2009). Inference is performed according to the Bayesian approach to enhance the

observed data with prior information coming from other case studies.

A great effort is devoted to the elicitation of prior knowledge by exploring one of the

richest databases of macroseismic fields, the Italian DBMI11 database (Locati et al.,

2011); in particular we examine 298 macroseismic fields covering all the Italian territory

and corresponding to the earthquakes of MCS ≥V that occurred in Italy from 1500 and

had at least 40 data points. Through a hierarchical agglomerative clustering method, the

macroseismic fields are grouped into four classes characterized by similar attenuation

trend The remaining, less informative (with less than 40 data points) macroseismic fields

of DBMI11 are then associated to one of the four classes by using a classification tree

built with the 298 more informative macroseismic fields. In each of the classes and for

every I0, a prior distribution of the p(d) parameter is assigned in correspondence to

different circular bins drawn around the epicentre; then, the α and β hyperparameters are

updated through the information contained in the macroseismic fields of the class, and the

posterior distribution of p is obtained which generates the probability distribution of Is at

any distance. Given the epicentral intensity I0, the mode of the corresponding probability

distribution of Is is taken as estimator of the intensity at site and used to forecast future

damage scenarios expressed in terms of macroseismic intensity.

In the framework of the European project “Urban Prevention Strategies using

MAcroseismic and Fault sources” (UPStrat-MAFA), this method has been applied in

some European test areas: South Iceland, Alicante-Murcia region (Spain), Mt.Etna (Italy),

Azores Islands and Portugal. After identifying the class, among the four classes of Italian

76

macroseismic fields, with the attenuation most similar to that of the current data (in case,

applying a shrinkage spatial coefficient), we adopt the corresponding distribution of Is as

prior information. The estimation procedure is then repeated for each dataset. Specific,

problematic aspects have been solved regarding the anisotropic attenuation trend (Azzaro

et al., 2013) and the intensity decay of offshore earthquakes.

This work has been co-financed by the European project “Urban Prevention Strategies

using Macroseismic and Fault sources” (UPStrat-MAFA - Num.

230301/2011/613486/SUB/A5), DG ECHO Unit A5.

References

-Azzaro R., D'Amico S., Rotondi R., Tuvè T., Zonno G. (2013). Forecasting seismic

scenarios on Etna volcano (Italy) through probabilistic intensity attenuation models: A

Bayesian approach, Journal of Volcanology and Geothermal Research, 251, 149-157.

-Locati M., Camassi R. and M. Stucchi (eds.), 2011. DBMI11, the 2011 version of the

Italian Macroseismic Database. Milano, Bologna, http://emidius.mi.ingv.it/DBMI11

-Zonno G., Rotondi R., Brambilla C. (2009). Mining Macroseismic Fields to Estimate the

Probability Distribution of the Intensity at Site, BSSA, 98, 5, 2876-2892, doi:

10.1785/0120090042, http://hdl.handle.net/2122/5039 "

77



We started a research for constructing a three-dimensional (3D) earthquake forecasting

model for the Kanto district in Japan under the Special Project for Reducing Vulnerability

for Urban Mega Earthquake Disasters for the 5 years (2012-2016). Because depth

distribution of earthquakes in this area ranging from shallower part to a depth of 80 km is

complex due to the subduction of the Philippine Sea and Pacific plates. We will develop

3D models with using a method of the Collaboratory for the Study of Earthquake

Predictability (CSEP). Although the CSEP experiment evaluates two-dimensional (2D)

forecasting models prospectively, our 3D model will be optimized for past seismicity in

this area retrospectively.

We aimed to search for a 3D testing area considering with a depth distribution of events

in the Kanto district. For the study, we used the relative intensity (RI) model (Nanjo,

2011), which is a forecasting model for 2D testing region. We extended RI model to 3D

testing area and applied to 2D and 3D areas described as follows and evaluated the RI

model performance on the basis of S-test’s log-likelihood score.

Firstly, we defined the 3D testing region with a horizontal grid of 0.1° and every 10 km

in a depth from 0 km to 100 km because some modelers in the Japanese CSEP

(CSEP-Japan) suggest the Kanto testing region with a grid of 0.05° squares with one

depth bin (0-100km) is too fine. Secondly, we evaluated with forecasts results of both 2D

and 3D testing region of the round (1 Nov, 2009 - 1 Feb, 2010), adapting to RI model

with smoothing radii ranging from 2.5km to 100km. The log-likelihood score of 3D

testing region showed much better than that for 2D one for all smoothing radii. We

concluded that 3D RI forecasting model is better than 2D one for Kanto district. The

difference between 2D and 3D model’s log-likelihood score indicated the 3D RI model’s

improvement of high earthquake expectations of location at the Izu peninsula with the

depth of 0 - 10 km and off Choshi areas with the depth of 40 - 50 km. Lastly, we

investigated effects of horizontal resolutions, testing with 0.02°, 0.05° and 0.2°squares

and further four rounds of 3 months forecasting periods after 1st February in 2010. The

log-likelihood scores of the 3D RI model for the 3D testing region also resulted in the

best performance with the smoothing radii of 5 - 10 km, which means that horizontal

resolutions and forecasting periods did not affected on the forecasting performance. In the

presentation, we will show our results and discuss our future plan.

78

The authors thank the Japan Meteorological Agency for the earthquake catalog. This

work is sponsored by the Special Project for Reducing Vulnerability for Urban Mega

Earthquake Disasters from Ministry of Education, Culture, Sports and Technology of

Japan.

Comparison of recent seismic hazard models based on the

Gutenberg-Richter magnitude-frequency relation


Many different ways are explored to study earthquakes since scientists have been trying

to understand earthquake process for centuries. The exponential model of earthquake

frequency-magnitude relation is a way to examine seismic activity in an area, which

implies that earthquakes follow the Gutenberg-Richter(GR) relationship: lnN = a-bM,

where N is the number of earthquakes, a-value is the number of earthquakes of M>0,

b-value is the slope of the distribution, and M is magnitude (Gutenberg and Richter,

1944). The estimation of the b-value of the GR law and its uncertainty is crucial in

seismic hazard studies, as well as in verifying theoretical assertions, such as the

universality of the GR. In spite of the importance of this issue, many scientific papers still

adopt formulas that lead to different estimations (Marzocchi et al., 2003). There are a

number of seismic models the recently have been developed based on GR law. In this

paper, we review the different methods and assumptions used in the construction of the

GR model, and compare PSH maps produced from these models of Frankel (1995),

Bozkurt et al. (2007) and working group on China National Seismic Hazard Maps (2012),

with an aim toward identifying the factors responsible for the largest differences in

probabilistic seismic hazard (PSH).

Frankel (1995) developed a spatial smoothed seismicity model for mapping the seismic

hazard in the central and eastern United States, because of the limited knowledge of

seismic sources in the region. In this model, historical seismicity is used to obtain the

b-value and a-value distribution over the study region. The steps leading to the final

hazard results include (1) bin the earthquake to each gird cell to get the total number ni of

earthquakes for cell i; (2) convert the cumulative ni to its incremental value according to

Herrman(1977), which is the number of events from M to M+△M in cell i; (3) use the

b-value to convert the incremental number of events for M≥4 to the number for M≥0; (4)

smooth and normalize the incremental values. The basic assumption behind this model is

that future moderate background earthquakes will be located near the historical events of

M≥4. This model is used and improved by some scientists such as Cao (1996) and

Hiemer et al. (2012).

79

Bozkurt et al. (2007) calculated the time-averaged (Poisson) probability of severe shaking

by using more than 10,000 intensity observations recorded since AD 1600 in a 350

km-wide box centered on Tokyo. Unlike other hazard assessment models, the intensity

observations are used in this model. The b-value in the entire study region is estimated

and makes it fixed in each grid cell. The a-value is estimated by the seismicity in each

cell without smooth used in Frankel model. And the a-value in each grid cell is different.

Working group on China National Seismic Hazard Maps (2012) is now making the 5th

national PSH map. The b-value and V4 (annual rate of magnitude greater 4) is estimated

using the seismicity with different magnitude and time span from the entire study region.

And the b-value and V4 is finally determined by artificial regulation according to the

expert advice. And then the seismicity annual rate is divided by the tectonic sources with

spatial distribution function, which represents the likelihood of earthquake occurred in

potential source areas.

The main difference of the three models is how to estimate b-value, and how to divide the

a-value or annual rate from the entire study region into each cell. The first model (Frankel,

1995) and the second model (Bozkurt et al., 2007) estimate the b-value using seismicity

from the entire study region, and the a-value using seismicity in each grid cell and

smooth the a-value. One thing to be noted is that seismicity used in the second model is

intensity data not earthquake catalog. The third model (working group on China National

Seismic Hazard Maps, 2012) estimates b-value and V4 using the seismicity with different

magnitude and time span from the entire study region. And the b-value and V4 is finally

determined by artificial regulation according to the expert advice. The first and second

model divide a-value (or annual rate) using grid cell statistics, and the third model using

tectonic sources.

Which one is better? What’s the effect on PSH? And do they have their own application

scope? In this paper, we will compare the difference and try to understand the reasons for

the difference, which should serve to focus future research aimed at resolving the

difference.

80

Numerical simulations of postseismic processes of the 1992 M7.2

Landers earthquake with a damage rheology model

Lifeng Wang,Vladimir Lyakhovsky, Yariv Hamiel, Yehuda Ben-Zion, and Matthias

Holschneider

Various studies indicate that brittle rock damage is an important feature of fault

zones,which may influence (and reflect past) earthquake and faulting processes.

However,due to theoretical and computational difficulties, rock damage is ignored in

most studies. Here, we construct a 3D Finite Element Model (FEM) that accounts for

evolving brittle fault zone damage using a nonlinear viscoelastic continuum damage

rheology. As a case study, we investigate the 1992 M7.2 Landers earthquake, and focus

particularly on the effect of damage in the fault zone on the aftershock activities. Our 3D

model (with dimension of 250X250X50km) involves the sediment layer, elastic layer,

inelastic layer and the damage fault zones that cutting through the elastic layer. We define

the initial stress field as the superposition of the stress change produced by the coseismic

rupture of the Landers earthquake and a tectonic stress field, which is simply formulated

as an arctan function depending on the distance perpendicular to the Landers fault. A

variable force boundary condition is applied to the lateral sides of the model, while the

bottom is fixed. The pressure/temperature dependent rheological parameter is determined

according to the local geological and geophysical data, while the damage related

rheological parameter is calibrated based on the observed aftershock activities of the

Landers earthquake. Based on the damage rheological model that constrained by both

geological and geophysical information, we investigate the impact of damage in the fault

zone on the aftershock activities, as well as on the aseismic deformation process.

81

Evaluation of annual, global seismicity forecasts, including ensemble

models


In 2009, the Collaboratory for the Study of the Earthquake Predictability (CSEP) initiated

a prototype global earthquake forecast experiment. Three models participated in this

experiment for 2009, 2010 and 2011—each model forecast the number of earthquakes

above magnitude 6 in 1x1 degree cells that span the globe. Here we use likelihood-based

metrics to evaluate the consistency of the forecasts with the observed seismicity. We

compare model performance with statistical tests and a new method based on the

peer-to-peer gambling score. The results of the comparisons are used to build ensemble

models that are a weighted combination of the individual models. Notably, in these

experiments the ensemble model always performs significantly better than the single

best-performing model. Our results indicate the following: i) time-varying forecasts, if

not updated after each major shock, may not provide significant advantages with respect

to time-invariant models in 1-year forecast experiments; ii) the spatial distribution seems

to be the most important feature to characterize the different forecasting performances of

the models; iii) the interpretation of consistency tests may be misleading because some

good models may be rejected while trivial models may pass consistency tests; iv) a

proper ensemble modeling seems to be a valuable procedure to get the best performing

model for practical purposes.

82

Short-term foreshocks in Southern California and Italy as

non-triggered events


The occurrence of earthquakes is commonly described as a triggering process where

single earthquakes act as activators for subsequent ones. This principle is the basis of the

Epidemic-Type Aftershock Sequence (ETAS) model of Ogata (1988) where all

earthquakes are described by the same underlying process and it has recently

been claimed that foreshocks are undistinguishable from the remaining seismicity (e.g.,

Hardebeck et al., 2008; Marzocchi & Zuang, 2011).

This approach implies that mainshocks are unpredictable. Physical processes that may

influence the foreshock appearance are not considered in ETAS. Therefore a better

understanding of foreshock sequences is necessary.

We first reproduce the study of Marzocchi & Zhuang (2011) and verify that ETAS

performs well in describing the observed overall seismicity in 30 years from a "bird's

eye" view with any cut off magnitude for Southern California and Italy. However we

show that as soon as we zoom into short-term foreshock "sceneries", ETAS fails to

explain the foreshock behaviour for low Mcut. We measure the foreshock behaviour in

Southern California and Italy by comparing different quantities of the observed

and ETAS simulated catalogs. These are: number of mainshocks, number of foreshock

sequences and number of foreshocks per sequence. The magnitude of the mainshock is

chosen to be M6+ and foreshocks are defined according to the nearest-neighbor cluster

method of Zaliapin et al. (2008). The comparison is made for different Mcut, ranging

between 2 and 4.

We show that the number of foreshocks per foreshock sequence observed before large

earthquakes (e.g. Landers or L'Aquila) is incompatible with ETAS statistics. Our

study shows the importance of small magnitude events (microseismicity) as potential

precursors of large events. Differences in the quantities described above, between

observed and simulated catalog, get larger for smaller Mcut. Moreover, as foreshocks are

shown to be non-systematic and a lot less frequent than aftershocks, their weight is

under-evaluated by the ETAS model. Finally we describe the Non-Critical Precursory

Accelerating Seismicity Theory (N-C PAST) of Mignan (2012), which is a candidate to

explain the abnormal foreshock statistics observed in California and Italy.

83

A statistical study on seismo-ionospheric anomalies of the total electron

content associated with worldwide large earthquakes during 1998-2012

Y. I. Chen at Institute of Statistics, National Central University, TAIWAN; J. Y. Liu at

Institute of Space Science, National Central University; C. H. Chen at Department of Earth

Science, National Cheng Kung University, TAIWAN; H. F. Tsai at GPS Science and

Application Research Center, National Central University, TAIWAN

This paper reports statistical results of seismo-ionospheric anomalies (SIAs) of the total

electron content (TEC) in the global ionosphere map (GIM) associated with worldwide

large earthquakes during 1998 - 2012. To detect SIAs, a quartile-based (i.e. median-based)

process is performed. The earthquakes are sub-divided into various regions to have a

better understanding on SIA characteristics. The earthquakes without being led by

magnetic storms are further isolated to confirm the SIA existence. Results show that the

SIA could significantly either increase and/or decrease in the afternoon/evening period

few days before the large earthquakes.

84

Assessment of completeness and homogeneity of aftershock catalogue of

2001 MW 7.7 Bhuj earthquake

S.K. Aggarwal, B.K. Rastogi, P.K. Khan, A.R. Bansal, and S. Kumar

A large earthquake of MW 7.7 occurring in Bhuj area (Lat. 23 - -

on January 26, 2001 is still followed by aftershocks of magnitude up to 5.0. The area is a

seismically very active intraplate region of western India, and appears to be a natural

seismic laboratory to seismologists. We have compiled more than 13000 aftershocks of

this earthquake till date. These events were acquired by many national agencies but a

single homogeneous catalogue does not exist for the region so far. We have categorized

these events based on magnitude viz. M < 2.0, 6400; 2.0 ≤ M < 3.0, 3900; 3.0 ≤ M < 4.0,

2174; 4.0 ≤ M < 5.0, 486; 5.0 ≤ M < 6.0, 49; M ≥ 6.0, 2. Further, the homogeneity and

completeness magnitude (Mc) of these events were assessed using maximum curvature of

the frequency - magnitude distribution from power law by Wiemer and Wyss (2000) for

statistical analysis. The catalogue of the events is found complete and homogenous for

Mc ≥ 3.0 up to 2004, and the Mc was improved to 2.0 later in the year 2005 due to

deployment of additional seismographs by National Geophysical Research Institute,

Hyderabad. The catalogue completeness was further reduced to 1.5 in the year 2008

because of additional dense network of Institute of Seismological Research, Gandhinagar.

Finally, the b value was estimated based on the homogenous and complete catalogue of

Mc ≥ 3.0 using maximum likelihood method of Aki (1965), and found to be 1.06.

Key words: Catalogue, Bhuj, Mc, b - value.

References

1. Wiemer, S., and M. Wyss (2000). Minimum magnitude of completeness in

earthquake catalogues: examples from Alaska, the western US and Japan. Bull. Seism.

Soc. Am. 90, 859-869.

2. Aki, K. (1965). Maximum likelihood estimate of b in the formula log N=a- b M

and its confidence limits. Bull. Earthquake Res. Inst. 43, 237-239."

85


Xiaowei Chen and Aitaro Kato

We search for “burst-like” clusters that are spatially-temporally isolated from background

seismicity from JMA catalog between 2000 and 2013. Specifically, we require the cluster

has at least 50 events within 14-day and 2-km, and fewer than 5 events during 14-day

prior to this cluster. The search results with 295 clusters, 93 of them occur within 2-km of

at least one other cluster. We identify 22 regions with repeating occurrence of seismicity

clusters, such repeating feature may represent periodic fluid intrusion or slow slip events.

Best-fitting ETAS parameters: μ0, K, c, α and p are computed for each area with

maximum likelihood method (Ogata 2006). Different behaviors are observed for

seismicity within proximity to active volcanoes (≤ 20 km) and seismicity further from

volcanoes. For non-volcanic seismicity, both α(≈1.2) and p (≈1.1) are nearly constant

among different regions. However, for 14 regions near volcanoes, strong spatial and

temporal variations of ETAS parameters are observed: α varies from 0.2 to 1.4, and p

varies from 0.8 to 1.5. Among them, Izu-Tobu and Miyakijima volcano exhibit very low

α (< 0.5) and high p (> 2). Strong temporal variations of ETAS parameters are observed

for volcanic regions, especially for Miyakijima region. During the 2000 eruption,

extremely high p and low α are observed, and both return to normal values after 2001.

We will analyze more detailed temporal variation of these parameters using moving-time

window, which may help to identify time periods with abnormal external forcing, e.g.,

dike intrusion. We hope to characterize seismicity clustering in: different tectonic

environments, different types of volcanoes, and different stages of volcano activities.

86

Statistical study of ULF seismo-magnetic phenomena at Kakioka

Observatory


In order to verify and clarify the ULF seismo-magnetic phenomena, a statistical

investigation of the relation between magnetic anomalies and local seismicity has been

performed. Geomagnetic data observed during 2001~2010 at the Kakioka observation has

been analyzed. Energy of ULF geomagnetic signals at the frequency around 0.01Hz has

been investigated by wavelet transform analysis. To identify anomalous changes induced

by ionospheric disturbances, the Kanoya station has been chosen as a reference station.

Statistical studies by superposed epoch analysis (SEA) have indicated that before a

sizeable earthquake there are clearly higher probabilities of ULF anomalies than that after

the earthquake: statistical results of daily counts were found significant at about 30 days

before, 2 weeks before, 5-7 days before and 2 days after the event. These results are

somehow consistent with previous studies in Izu and Boso Peninsulas, which suggests a

correlation between ULF geomagnetic anomalies and local seismicity.

87


Matt Gerstenberger, Jeremy Zechar, and David Rhoades

Having useful testing of earthquake forecast models is reliant on having enough high

quality data to provide informative results. To date, the RELM & CSEP experiments have

been testing and producing results for both short-term (24 hour) and long-term (5-year)

models using a 5-year testing period. To provide reliable results the testing period should

produce statistically powerful results and also results that are representative of what is

expected over a longer time period. Here we examine both of those assumptions. Using

the RELM models we investigate how many earthquakes are required to produce

statistically powerful results. With most models, our results indicate that a powerful test

is possible within a 5-year period; however when investigating the effect of

non-stationarity of seismicity, the results are not so clear. Using different forms of

bootstrapped catalogues, we have tested the models over many different time periods.

Our preliminary results indicate that the results are more inconsistent than one would

expect based on random chance.

88

Sensitivity of aftershock rates for a Wellington fault earthquake to

different parameters.

Annemarie Christophersen, David Rhoades and Sebastian Hainzl.

We investigate the sensitivity of the number of large aftershocks (NAS) for three

aftershock models to changes in model parameters. The three models are the Short-Term

Earthquake Probability (STEP), for which we calculated the average NAS for a set of

parameters, and two implementations of the Epidemic Type Aftershock (ETAS) model,

for which we run a number of simulations. The model parameters are the p-value that

controls the temporal decay of aftershock activity, the b-value of the

magnitude-frequency distribution of earthquakes, the productivity constant that is

formulated in different ways for each of the three models, and mmax, the maximum

allowed magnitude for aftershocks. For all models NAS is sensitive to the parameter

changes that cover ranges well within observations for New Zealand aftershock

sequences. The sensitivity to parameter variations is much stronger for the ETAS model

than for the STEP model. Further, the range of NAS for the ETAS model with the

medium set of parameters is larger than the range of NAS for the STEP model with

varying parameters. The results of this sensitivity analysis contributes to two on-going

larger projects: (1) the task of the ‘It’s Our Fault Project’ to investigate whether there are

any potential deficiencies in the currently used probabilistic Wellington earthquake

design spectra due to the exclusion of aftershock, and (2) an EQC funded project to

investigate the likelihood of late and large aftershocks from global earthquake catalogues.

89

Spatiotemporal variation of the b-value and its tectonic implications


Institute of Theoretical and Applied Geophysics, School of Earth and Space Sciences,

Peking University, Beijing, China.

Introduction

The North China Region has abundant historical seismicity records superior to other

areas of China. Wang et al. (2011) discussed the seismic hazard in the North China

Region by analyzing the spatial distributions of b-values. However, their estimation

method has obvious drawbacks. First of all, due to the heterogeneous distribution of

microearthquakes, accurate estimates of the b value are difficult to be obtained in some

areas of North China. In addition, their choice of the size of the space-time window was

quite subjective, which brought difficulties in evaluating the error of estimates. In this

paper, a 2-D spline function is considered for the logarithm of the b-value at each

location in the North China Region and an objective Bayesian method is adopted to

obtain the optimal estimate of such functions. Our method is modified from Ogata et al.

(1990) and it has shown to overcome effectively the drawbacks that are mentioned above.

By applying our method to the earthquake catalog from the North China Region, we

obtained a much more stable and integrated spatial map of variations of the b-value.

In the present paper, we use the Bayesian approach with smoothness prior to estimate and

interpolate b-values in space. Since many parameters are required for the spline function,

we maximize the log-likelihood function which measures the goodness of fit to the data

to obtain parameter estimation. On the other hand, we adopt the objective Bayesian

procedure method to avoid unnecessary fluctuation of an estimated spline surface.

Synthetic test

To validate our approach of using B-spline functions to calculate the spatial variation of

b-value, we designed a synthetic catalog of events with a minimum magnitude of

completeness Mc=2.0. Magnitudes above Mc 2.0 follow a Gutenberg-Richter law with

the b-value fluctuating along the function b(t)=1.0+0.2sin(2pi*t)+0.2sin(3pi*t). Below

Mc 2.0, we assume that no events are detected. For simplicity, we adopt a 1-D model

with a length of 20 years. The time period from the 8th to the 10th year is designed to

represent low seismicity time zone where effective b-value cannot be obtained using

traditional methods. Both the traditional MLE method and our Bayesian approach are

90

used to simulate b-value in this model and the result shows that our approach enjoys an

obvious advantage. Effective b-values of the low seismicity time period cannot be

obtained by MLE method but are successfully calculated using our approach. In areas

where both methods can function, the result shows that the Bayesian approach also

performs better.

Application to the North China Region

In this study, we focus on the region bounded by the 108°E and 124°E meridians, and the

32°N and 42°N parallels, which includes most of the North China Region The earthquake

catalogue we used is complied by China Seismology Bureau between the year 1985 and

the year 2012. We divide the area of North China Region into rectangular subareas with

sides of in both meridian and parallel. Taking detection ability into consideration, we

have 10760 effective events in the considered time period from 1977 to 2008 with a

minimum magnitude of completeness of M2.5.

Computational results show significant variations in the b-value ranging from b≈0.55 to

b≈1.65 in the North China Region. We interpret the spatial pattern of the b-value to be an

indicator of stress distribution in the North China Region. Regions with low b-values

include the Yuncheng Region in the Shanxi Rift, the Zhengzhou Region in the

Anyang-Heze-Linyi Zone and the Zhangjiakou-Bohai Tectonic Zone. These regions have

shown relatively higher seismicity than the other areas in the North China Region and

therefore are likely to have higher stress accumulations. We have also investigated the

temporal changes in b-value in two specific areas: the Zhangjiakou-Bohai Tectonic Zone

and the Huabei plain seismic zone. We believe an abrupt temporal change in b-value is a

sign for recent tectonic events that took place in the North China Region. The 1998

Zhangbei M6.2 earthquake may be the main cause for the continued increase in the

b-value in the Zhangjiakou-Bohai Tectonic Zone from the year 1998 to the year 2004. In

approximately the same time period however, the Huabei plain seismic zone has

experienced a drop of 0.4 in b-value. Some tectonic events may have happened in the

vicinity that lead to such a significant drop.

Reference

Ogata, Y., Imoto, M. & Katsura, K., 1991.3-D spatial variation of magnitude-frequency

distribution beneath the Kanto District, Japan., Geophys,J.Int.,104,135-146

Wang, H., Cao, J. & Shen, X., Background seismicity and its application to seismic

hazard assessment in the North China Region. Earthquake, Vol.32, No.2

91


J.Douglas Zechar1, J.L. Hardebeck2, A.J. Michael2, M. Naylor3, S. Steacy4, S. Wiemer1, J.

Zhuang5

1ETH Zurich, SWITZERLAND 2United States Geological Survey, Menlo Park, USA 3University of Edinburgh, SCOTLAND 4University of Ulster, NORTHERN IRELAND 5Institute of Statistical Mathematics, Tokyo, JAPAN

Statistical analysis is critical to the understanding of seismicity, the evaluation of proposed

earthquake prediction and forecasting methods, and the assessment of seismic hazard. Unfortunately,

despite its importance to seismology-especially to those aspects with great impact on public

policy-statistical analysis is mostly ignored in the education of seismologists, and there has been no

central repository for the relevant software tools. To remedy these deficiencies, and with the broader

goal to enhance the quality of statistical seismology research, we have begun building CORSSA, the

Community Online Resource for Statistical Seismicity Analysis (www.corssa.org). The targeted

readers/users of CORSSA range from beginning graduate students to experienced researchers.

CORSSA materials are organized with respect to six themes: introductory material, basic features of

seismicity, statistical foundations, seismicity catalogs, models and techniques, and earthquake

predictability. As of this writing, a dozen articles have been published and others are being drafted.

Each article is peer-reviewed and presents a balanced discussion, including illustrative examples and

code snippets. Topics covered so far include: exploratory data analysis, identifying quarry blasts,

estimating the magnitude of completeness, earthquake location accuracy, spatiotemporal models of

seismicity, declustering, earthquake triggering, seismicity rate changes, and evaluating earthquake

forecasts. We have also begun curating a collection of statistical seismology software packages.

CORSSA also includes forums for discussion, a glossary of commone terms, and news about upcoming

meetings, special issues, and recent papers. We are actively seeking new contributors, both for topics

that have already been identified and new topics related to this field.

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