pacific tsunami warning center: introduction to tsunamis and ptwc operations

Pacific Tsunami Warning Center

INTRODUCTION TO TSUNAMIS

and PTWC OPERATIONS

22 June 2015 for NDPTC Interns

Brian Shiro ([email protected])

What is a Tsunami?

What is a Tsunami?

• A series of long-period waves created by a sudden disturbance that displaces a large amount of water.

• Sometimes incorrectly called “tidal waves” or “seismic sea waves.”

“tsu” = harbor

“nami” = wave

pronounced: soo-NAH-mee

Where do Tsunamis Occur?

59% 25%

12% 4%

Pacific

Mediterranean

Atlantic

Indian

Whole Historical Record

77%

9%

10% 4%

Pacific Mediterranean Atlantic Indian

Just 1900-present (no Mediterranean bias)

Plate Boundaries

Pacific Ring of Fire

Hawaii

What Causes Tsunamis?

Thus, the tsunami warning system relies primarily upon rapid earthquake detection and characterization.

72%

10%

5% 2%

11% Earthquakes

Landslides

Volcanoes

Atmosphere

Other/Unknown

Fatal Tsunamis 1900-2011

COMET pool video Meteor (rare) Earthquake (most common)

Landslide/Volcano (surface)

Landslide/Volcano (subsurface)

1.  What is a tsunami? 2.  Where do most tsunamis occur? 3.  What most commonly causes a tsunami?

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Learning Check

Tsunami Characteristics

Tsunami Speed

About 600 mph

Speed (v) depends only

on water depth (h).

V = √ (g*h)

h

Called “Deep Water Waves” because h > L/2

L

h h

Called “Shallow Water Waves” because h < L/20

L

h

Normal vs. Tsunami Waves

Normal Waves •  Movement of uppermost layer

of water only •  Caused by wind •  Wavelength: feet •  Period: seconds •  Speed: ~ 50 mph •  You can surf them.

Tsunami Waves •  Movement of entire water

column down to sea floor •  Caused large water

displacement •  Wavelength: miles •  Period: minutes •  Speed: ~ 500 mph •  You cannot surf them!

Tsunamis in Deep vs. Shallow Water

In the open ocean •  Extremely long wavelength > 60

miles •  Height is usually < 3 feet

•  Travel at great speeds: ~ 500+ mph (jet plane)

In shallow coastal waters •  Wavelength shortens to 15 feet,

and waves “pile up” •  Height grows (up to 30+ feet)

•  Speed slows dramatically to ~ 30 mph (still faster than you can run!)

(~ 3 miles) (~ 3000 ft.) (65 ft.)

(30 mph) (210 mph) (520 mph)

Inundation vs. Runup

Inundation •  The horizontal distance inland

that a tsunami penetrates, generally measured perpendicularly to the shoreline.

•  Can reach several miles

Runup •  The vertical height between the

elevation of the maximum tsunami inundation and the sea level at the time of the tsunami.

•  Can reach heights over 100 feet

A tsunami is more than one wave!

First may not be the largest. Later waves can carry more debris. Time between waves could be 10 to 60 minutes. Danger lasts for hours.

Tsunami from the March 2011 Japan event recorded in Oregon

Why Tsunami Warning Works

Tsunami waves are fast, but seismic waves are much faster. • Tsunami wave speed

~ 600 mph • Seismic wave speed

~ 15,500 mph Therefore, it is possible to issue a warning for a tsunami ahead of its arrival!

1.  What controls tsunami speed? 2.  How are tsunamis different from normal ocean

waves? 3.  What is the difference between inundation and

runup?

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Learning Check

Effects of Tsunamis

Death

Since 1850, tsunamis have claimed more than 430,000 lives. All are preventable. People are unable to outrun fast-moving, steadily rising floodwater carrying debris. Most casualties result from debris strike trauma rather than drowning. Animal, plant, insect too 2004 Thailand

Destruction

Tsunamis can cause extreme destruction to: • Homes, Offices • Roads, Bridges • Boats, Cars • Sewer systems, Power

lines Most damage is caused by the huge force due to the mass of water behind the wave. Large objects such as ships and boulders can be carried several miles inland. Huge costs involved 2009 Samoa

Environmental Effects

Permanent changes to the landscape Destroy trees and habitats Water supply contamination Solid waste debris Toxic waste of hazardous materials (oil, industrial chemicals, sewage, etc.) contaminate soil and water. Salinization of land leads to long-lasting agricultural impacts.

2011 Japan

Secondary Effects

Disease from contamination of drinking water, malaria from stagnant water Homelessness Psychological effects (PTSD, depression) Radiation (Fukushima Power Plant)

2011 Japan

Learning Check

1.  What causes the most deaths during a tsunami? 2.  Why are tsunamis so destructive? 3.  Name an environmental effect of a tsunami?

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PTWC History and Responsibilities

PTWC History

▶  Established in 1949 (following 1946 tsunami)

▶  International center for Pacific since 1968 (following 1960 tsunami)

▶  Interim center for Indian Ocean 2005-2013 (following 2004 tsunami)

▶  Interim center for Caribbean Sea (since 2007)

▶  Moved from Ewa Beach to Ford Island (in 2015)

1946 Tsunami in Hilo 1960 Tsunami in Japan 2004 Tsunami in Thailand Caribbean Tsunami Potential PTWC’s Old Location

PTWC scientist staff tripled to 12 in 2005, allowing for 24x7 shift/standby operation.

Areas of Responsibility

Hawaii Guam/CNMI

Samoa

Puerto Rico / VI

PTWC’s domestic local warning areas

International Tsunami Warning Systems

Types of PTWC Messages

Domestic (U.S.) ▶  Hawaii ▶  American Samoa ▶  Guam and CNMI ▶  Puerto Rico and VI

International ▶  Pacific Ocean

countries ▶  Caribbean Sea

countries

Tsunami Warning

Tsunami Advisory

Tsunami Watch

Tsunami Information Statement

Tsunami Threat Message (major threat)

Tsunami Threat Message (coastal threat)

Tsunami Threat Message (marine threat)

Tsunami Information Statement (no threat)

Domestic Messages

Tsunami Warning Potential tsunami with significant widespread inundation (forecast >1 m) is expected in < 3 hr. •  Actions: Evacuate low-lying coastal areas, move

ships to deep water if there is time to safely do so.

Tsunami Advisory Potential tsunami may produce strong currents or waves dangerous to those in or near the water (forecast 0.3-1 m). •  Actions: Close beaches, evacuate harbors, move

ships to deep water if there time to safely do so.

Tsunami Watch Issued for an event which may later impact the area in 3-6 hr. •  Actions: Be prepared to act in case the event is

upgraded.

Tsunami Information Statement

An earthquake has occurred with no destructive tsunami threat (forecast <0.3 m) or is expected >6 hr. •  Actions: None

International Messages

Tsunami Threat Message (major threat)

Issued to areas having a coastal forecast > 3 m within 3 hr from earthquake magnitude >=7.9. •  Actions: Evacuate low-lying coastal areas, move


Tsunami Threat Message (coastal threat)

Issued to areas having a coastal forecast 1-3 m within 1000 km of the earthquake magnitude 7.6-7.8. •  Actions: Evacuate low-lying coastal areas, move


Tsunami Threat Message (marine threat)

Issued to areas having a coastal forecast 0.3-1 m within 300 km of the earthquake magnitude 7.1-7.5. •  Actions: Close beaches, evacuate harbors, move

ships to deep water if there time to safely do so.

Tsunami Information Statement (no threat)

Issued to areas having a coastal forecast < 0.3 m and a preliminary earthquake magnitude 6.5-7.0. •  Actions: None

Int’l Messages Then & Now

Before Oct 2014 ▶  Text only ▶  Forecast tsunami

arrival times ▶  Places assigned

Warning or Watch alert status

▶  Some conflict with national alert levels

▶  General response guidance

▶  Very conservative (over-warning)

After Oct 2014 ▶  Text, graphics, & stats ▶  Forecast tsunami times

& coastal amplitudes ▶  Only Threat Level

information given (no alert status)

▶  Reduces conflict with national alert levels

▶  More specific response guidance

▶  More precise (less over-warning)

Learning Check

1.  When did PTWC begin its operation? 2.  What areas does PTWC serve? 3.  How is a Threat Message different from a Warning?

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PTWC Operations

PTWC Operations Process

TWC’s prioritize speed over accuracy to determine preliminary earthquake parameters as rapidly as possible.

0-5 min Preliminary

Seismic Analysis

5-10 min Initial

Tsunami Message

10-20 min Continued

Seismic Analysis

20-30 min Tsunami Forecast Analysis

30-33 min Supplemental

Tsunami Message

33 min - 2 hr Sea Level

Gauge Analysis

Preliminary Seismic Analysis

>600 stations from IRIS,

USGS, IMS, etc.

0-5 min Preliminary

Seismic Analysis

5-10 min Initial

Tsunami Message

10-20 min Continued

Seismic Analysis



Tsunami Message


Gauge Analysis

Stations and Response Time

Sardina et al. 2011

from >70 min in 1992 …

… to <5 min in 2015

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The US tsunami warning centers’ (TWCs) have as their official primary responsibility to warn the public about the threat of tsunamis potentially generated worldwide. For this purpose they operate similarly to a seismological observatory in that scientists locate seismic events and estimate their magnitude. Unlike traditional seismic observatories, however, their mission requires the TWCs to determine the earthquake parameters as rapidly as technically possible. Estimation of the earthquakes’ location and magnitude subsequently leads to both the evaluation of their tsunami generating potential and a course of action based on pre-established criteria, as illustrated in Table 1 for the Pacific Basin. Relying on these criteria means that to issue a tsunami warning for the Pacific region it suffices to determine whether or not a shallow (less than 100 km depth) earthquake’s epicenter lies under or near the sea, and if its magnitude crosses the warning threshold, in this case magnitude 7.6 and above for the Pacific Basin.

�The TWCs have gradually adopted an operational model that sacrifices some accuracy of the preliminary earthquake parameters for the needed response speed. The critical character of their mission have also justified the TWCs sending their preliminary event parameters even ahead of the US institution considered authoritative regarding earthquakes, in this case the NEIC. During the last decade the US TWCs have in fact achieved processing and warning speeds that made some official directives obsolete sooner than expected. As influencing these operational improvements we can mention the following factors:

• An increasing density of the available seismic networks worldwide. Figure 1 illustrates the number and type of seismic stations available to the TWCs from 1992 to 2011. For many years the TWCs did not actually import all the available seismic data into their systems. In 1998, for instance, the PTWC ingested into its systems data from about two dozen of the 93 seismic stations available. As shown in Figs. 1 and 2, however, since 2004 the PTWC has more than doubled the number of seismic stations it monitors in near-real time.

• The adoption of faster magnitude estimation methods such as the broadband P-wave moment magnitude (Mwp) after Tsuboi et al., 1995 [1], 1999 [2]. The method has a tendency to incur larger magnitude underestimations for great earthquakes, as documented by Whitmore et al, 2002 [3], and Lomax and Michelini , 2009 [4]. Notwithstanding, the Mwp magnitude scale does not in fact saturate for mega earthquakes, as shown by Hara and Nishimura, 2011 [5], and still allows the estimation of an earthquake’s size with sufficient accuracy to determine whether or not its magnitude crosses the tsunami warning thresholds.

• An improved IT infrastructure, from faster computers with expanding memory and storage, to faster and more reliable internet connections.

Most traditional seismic observatories operate guided by a set of operational considerations that place parametric accuracy and catalog completeness, not extra speed, as their main priority. During this inherently hasten process, how much accuracy do the TWCs actually relinquish to gain a lot in response speed, and vice versa? Without analyzing a data set that allows to actually quantify and measure these variables the question remains without a valid answer.

By operating under the imperative of speeding up their seismic analyses a great deal, the TWCs have rather inadvertently accumulated a lot of information characterizing the quality of increasingly faster earthquake parametrizations. These data’s rather unique characteristics stem from the fact that while obtaining it the TWCs have systematically violated several of the earthquake processing rules considered as standard seismological practice. This list of “transgressions” include using Mwp, a non-standard magnitude estimation method, as the main technique applied to estimate the preliminary magnitudes, and sending messages containing hypocenter determinations with more than 180 degrees of maximum azimuth gap. These set of conditions motivated us to seize this rare opportunity to evaluate the quality of faster than normal earthquake parametrizations, assess their reliability, and make some recommendations regarding the daily operations of the tsunami warning centers.

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N 84Min 6:00Max 38:17Mean 14:06Median 13:53Std 4:30

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8.0 Sumatra7.9 Japan

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6.9 Rat Is.7.8 Chile

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7.9 Sumatra

8.5 Chile8.0 Sumatra

7.9 Japan

2003 2004 2005 2006 2010200920082007 47 6:15 34:58 10:58 9:41 4:58

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2011 51 4:25 22:36 8:57 8:19 3:18

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05/01/

07

08/31/

07

04/30/

08

08/30/

08

05/01/

09

08/31/

09

05/01/

10

08/31/

10

05/01/

11

08/31/

11

7.7

7.6

7.5

7.98.1

7.57.5

7.7

7.5

7.3 7.67.3

7.7

7.7

7.37.5

7.9

7.7

7.67.3

8.6

7.1

8.0

7.8 7.8

8.5

8.5

7.5

2003 2004 2005 2006 2010200920082007 41 0 0.7 0.26 0.3 0.16

32 0 1 0.19 0.1 0.2

27 0 0.5 0.2 0.2 0.14

30 0 0.7 0.2 0.15 0.2

17 0 0.5 0.2 0.2 0.15

20 0 0.5 0.16 0.1 0.13

41 0 1.6 0.2 0.2 0.2

N 23Min 0Max 0.6Mean 0.12Median 0.1Std 0.15

20 0 0.3 0.12 0.1 0.1

2011

0

10094 60 64

208


0

2827

84 2


16

5 7 9

1


610 10

4 2

811

62


0

24

P T

W C

E a

r t h

q u

a k

e

C

o u

n t

13

7 8

1 1

3

6

6

1 1

65

7

1 1

8

3

8

1

0

8

65

8

1 1

a) 2003 b) 2004 c) 2005 d) 2006

e) 2007 f) 2008 g) 2009 h) 2010

i) 2011 j) 2003~2011

PTW

C

PTW

C

WC

ATW

C

WC

ATW

C

Earthquakes Included in theObservatory Message Database

Observatory Message Delays Observatory Message Delays for Mw > 6.5 Bulletin Message Delays Azimuth Gap Statistics Observatory Message MagnitudeOffsets from GCMT Mw Number of Analyzed Earthquakes

1992 1994 1996 1998 2000 2002 2004 2006 2008 20101993 1995 1997 1999 2001 2003 2005 2007 2009 20110

100

200

300

400

500

Sei

smic

Sen

sors

Cou

nt

520 26 36

5180

93

128140

154171

192211

223

286315

346372

462

535

Bro

adba

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STS

-1,2

Oth

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MG

KSTrill

ium

Numbers and Types of Seismic StationsAvailable to the TWCs

Figure 1. Number and type of seismic stations available to the tsunami warning centers since 1992. In 1998 PTWC ingested seismic data from only two dozen of the available 93 broadband seismic stations. At present, PTWC ingests and monitors seismic data from a total of 535 seismic stations, including 468 broadband seismometers distributed worldwide.

1992-19981999-20042005-2011

Seismic Stations Available to the TWCs

Figure 2. Worldwide distribution of seismic stations available to the tsunami warning centers since 1992. Green squares illustrate the fact that since 2004 PTWC has more than doubled the number of stations it monitors in near-real time.

We compiled a database of 6031 observatory messages and 1994 tsunami bulletins issued by the TWCs between 2003 and 2011. Cross-validation of the TWCs’ epicenter locations with those issued by the NEIC, and the TWCs’ earthquake magnitudes with the moment magnitudes released by the GCMT project produced two databases with 1856 and 301 obs messages and tsunami bulletin entries, respectively. The combined analyses of these data support the following statements:

• The TWCs have gradually reduced their message products’ delay from thirteen and eighteen minutes back in 2003 to six and nine minutes in 2011 for obs messages and official bulletins, respectively. This represents a substantial improvement in actual tsunami warning capabilities.

• The TWCs fast hypocenter locations and magnitude values remain rather insensitive to the maximum azimuth gap incurred in the earthquake parametrizations. The average lateral offsets between the TWCs’ and NEIC’s epicenters remain under 60 km, well within the range acceptable for tsunami warning purposes, even for azimuth gaps as wide as 240 degrees.

• The TWCs’ average magnitude offsets do not vary from GCMT moment magnitudes by more than 0.2 magnitude units for azimuth gaps as wide as 280 degrees. Magnitude underestimations larger than the average 0.2 units for past great and mega earthquakes did not compromise the issuance of the required tsunami warning products.

• When estimating the earthquake magnitudes duty scientist at the TWCs should rely primarily on automated versions of the available magnitude calculation engines, particularly when applying the Mwp method.

Operational results demonstrate that doing so expedites the estimation process while also eliminating the negative influence of individual personal biases introduced when manually selecting individual station magnitudes from the Mwp moment rate plots. Duty scientists should resort to manually reviewing individual Mwp station estimates only when prompted by complex or unusual events.

• Making use of additional processing time to include more than five seismic stations in the magnitude averages does not significantly improve the accuracy of the preliminary Mwp magnitude estimates.

• As long as the US TWCs base the evaluation of the earthquakes' tsunami-generating potential on seismic processing techniques, counting with an IT infrastructure that allows the ingestion of seismic data in near-real time from the seismic stations increasingly available worldwide turns of paramount operational importance. Future projections for the TWCs should take into consideration not only the software components of the warning system, but also the real-time operational aspects of its IT infrastructure such as internet bandwidth and redundancy.

Given the TWC’s mission to protect lives and property, these findings make it difficult to justify longer seismic data analyses that use the already limited time available for coastal evacuations, particularly in the earthquake’s near field. Furthermore, the results demonstrate that current procedures at the US TWCs routinely generate quick earthquake parameters with sufficient accuracy for most initial tsunami warning operations. Some regional seismic observatories could consider applying the TWCs’ methods to expedite the release of their preliminary earthquake parameters as well.

Acknowledgments

We express our gratitude to all present and past duty scientists at PTWC and WCATWC for contributing to the stream of tsunami messages issued by the TWCs from 2003 to 2011.

References

[1] Tsuboi S., Abe K., Takano K., and Yamanaka Y. (1995). Rapid determination of Mw from broadband P waveforms, Bull. Seis. Soc. Am. 83 606-613

[2] Tsuboi S., Whitmore P., and Sokolowski T. (1999). Application of Mwp to deep and teleseismic earthquakes (1999). Bull. Seis. Soc. Am. 85-5 1,345-1,351

[3] Whitmore P., Tsuboi S., Hirshorn B., and Sokolowski T. (2002). Magnitude dependent correction for Mwp, Science of Tsunami Hazards, 20-4 187-192

[4] Lomax A. and Michelini A. (2009). Mwpd: a duration amplitude procedure for rapid determination of earthquake magnitude and tsunamigenic potential from P waveforms, Geophys. J. Int. 176 200-214

[5] Hara T., Nishimura N. (2011). Numerical experiments to investigate the accuracy of broadband moment magnitude, Mwp, Geophys. J. Int. 187 1,537–1,559

Conclusions

Introduction Earthquakes Included in theBulletin Message Database

Figure 3. Location of the 1856 earthquakes included in the observatory messages’ database.

Figure 4. Location of the 301 earthquakes included in the bulletin messages’ database.

Figure 5. Observatory messages’ delay in minutes after origin time for 1856 earthquakes evaluated by the TWCs from 2003 to 2011. The thick lines represent the average delay (mean) through the years. PTWC (top), and WCATWC (bottom).

Figure 6. Observatory messages delay in minutes after origin time for earthquakes with moment magnitudes larger than 6.5 from 2003 to 2011. The thick lines represent the average delay (mean) through the years. The labels indicate the magnitude estimates after PTWC (top), and WCATWC (bottom).

Figure 7 (above). Bulletin messages delay in minutes after origin time for earthquakes with GCMT moment magnitudes 6.5 and larger from 2003 to 2011. The thick lines represent the average delays (median) through the years. The labels indicate the magnitude estimates after a) PTWC, and b) WCATWC.

Figure 8 (right). Behavior of core statistics including the mean, median, maximum, minimum, and standard deviation (Std) for intervals of the maximum azimuth gap incurred by PTWC (top) and WCATWC (bottom) in their hypocenter determinations. From top to bottom: a) Epicenter lateral offsets from NEIC locations, b) Magnitude offsets from GCMT moment magnitudes, c) Number of seismic stations used in the magnitude estimations, and d) Observatory message delay after origin time.

Analysis of the Number of Seismic Stationsused in the Magnitude Estimations

Figure 9. Observatory messages’ magnitude offsets for earthquakes with GCMT moment magnitude 6.5 and larger. The thick lines represent the median of the absolute value of the magnitude offsets through the years as listed on top of the plot. The symbols indicate GCMT moment magnitude intervals, while the labels list the magnitude estimates after PTWC (top), and WCATWC (bottom).

Figure 10. Histograms showing how many earthquakes the TWCs characterized with magnitude averages of up to 5, 7, 11,17, and 21 seismic stations from 2003 to 2011. a), b), c), d), e), f), g), h), i), and j) correspond to PTWC, while k), l), m), n), o), p), q), r), s), and t) correspond to WCATWC.

(a)

(b)

(c)

(d)

(a)

(b)

(c)

(d)

Mo

re B

andw

idth

Mw ≥ 7.9 Expanding Watch-Warning7.6 ≤ Mw ≤ 7.8 Regional Tsunami Warning

Basin-crossing Tsunami Pacific-Wide Warning

6.5 ≤ Mw ≤ 7.5 Tsunami Information BulletinMw < 6.5 Observatory Message

Magnitude Interval Message Product

Table 1. Magnitude criteria applied when issuing tsunami message products to the Pacific Basin region.

Quick-and-Dirty Earthquake Parametrizations: Why Short Analysis Times with Big Azimuth Gaps suffice for Initial Tsunami Warning Operationsby V.H.R. Sardiña, N.C. Becker, S.A. Weinstein, G. Fryer, K. Koyanagi, D. Wang, D. Walsh, and C. McCreery (all at: NOAA/NWS/Pacific Tsunami Warning Center, `Ewa Beach, HI, USA (please send email to: [email protected])

From 2003 to the beginning of 2006 both TWCs issued their messages in about thirteen minutes after origin time. From 2006 onwards, however, while WCATWC systematically reduced the messages delay PTWC continued essentially at the same level until 2008. We can attribute the PTWC message delay trend to a combination of the following factors:

• Insufficient bandwidth until spring of 2008. The addition of more internet bandwidth in May and August of 2008 had a tangible impact on PTWC’s response speed, as it allowed the ingestion of most of the seismic stations shown in Fig. 1 into its systems. More density of stations translates into faster locations and magnitude estimations, which in turn lead to faster messages.

• Implementation of an automatic version of the Mwp calculation engine. Before 2010, to obtain an Mwp-based magnitude estimation at PTWC the duty scientists had to manually pick the maximum peak values directly from moment rate plots. The implementation of an automatic Mwp calculation engine has not only led to systematically shorter processing times, but also to a considerable reduction of the otherwise unavoidable personal biases from the estimation process.

• The last, but no less important factor influencing the reduction of processing time at PTWC has to do with a partial mindset shift among the duty scientists. For many years duty scientists continued to carry out the preliminary earthquake analysis adopting a very conservative approach that placed undue weight on the ideal of accuracy. Such

cautious approach made sense when confronted with a sparsely distributed network of seismic stations, but not when seismic networks have increased their density of stations to the current level shown in Figs. 1 and 2.

The TWCs issue a tsunami information bulletin (TIB) for earthquakes with magnitudes between 6.5 and 7.5 inclusive, and tsunami warnings and watches of varying severity for any earthquake with a 7.6 or larger magnitude. Consequently, responding to these moderate and large events as fast and accurately as possible turns of paramount importance. Figure 6 illustrates the obs messages’ delay incurred while processing these events at both TWCs. In addition to a progressive reduction of the message delay, when compared with the plots presented in Fig. 5 it turns clear that when dealing with larger events both TWCs tend to send their obs messages at least half a minute faster than for smaller events.

Taking the medians listed in Figs. 5 and 6 as representative of the yearly message delay distributions we can say that, on average, as of 2011 both TWCs routinely issued their obs messages within a similar timeframe of about six minutes. The twenty or thirty some seconds difference between their means falls mostly within the level of noise. We can state this on the grounds that the TWCs use similar but not the same data and tools within two different operating environments.

Although the obs messages illustrate the improvements in terms of operational speed, both TWCs send them as non-official message products intended for selected institutions, mainly other seismic observatories. Figure 7 illustrates the delays for actual tsunami bulletins issued between 2003 and 2011. We find it worth clarifying that the relatively longer

delays incurred by WCATWC stem from the fact that the protocol in place requires both warning centers to coordinate their message parameters. Most moderate and great earthquakes occur within the PTWC AOR, which means that more often than not WCATWC most gather PTWC’s earthquake parameter before issuing its own official message products, even to customers in its AOR. Analysis of Fig. 7 together with Fig. 5 and 6 allow us to make the following observations:

• Taking the median or mean as representative of the yearly distribution of bulletin delays we can say that, on average, both TWCs have reduced the time needed to issue their tsunami warning bulletins from eighteen minutes back in 2003 to nine minutes in 2011. This represents a substantial improvement in actual tsunami warning capabilities.

• The trend in the reduction of the bulletin delays seen in Fig. 7 follows a similar trend to the one observed for PTWC in 5 and 6. Close examination of Figs. 5 and 6, however, makes apparent that although back in 2006 WCATWC had already started to reduce its obs messages’ delay ahead of PTWC the same does not apply to the overwhelming majority of official tsunami bulletins issued for events outside WCATWC’s AOR

• Some areas still present a challenge due to the lack of denser seismic networks. This problem turns particularly acute for the Southern Pacific, as illustrated in Fig. 2 and corroborated by the bulletin delays for some earthquakes in that region.

Analysis of Message Delays from 2003 to 2001

NA

TIO

NAL

OCE

ANIC

AND ATMOSPHERIC ADMIN

ISTRA

TION

U.S. DEPARTMENT OF COMMER

CE

Analysis of the Accuracy of the Earthquake Parameters with Increasing Azimuth Gaps

During the TWCs’ staff meetings, duty scientists routinely treat the epicenter and magnitude offsets, as well as the messages’ delay time as quality indicators within the context of tsunami warning operations. As observed in Figs. 8a the mean and median lateral epicenter offsets for both TWCs remain under 60 km even for azimuth gaps as wide as 240 degrees. Meanwhile, the absolute magnitude offsets shown in Figs. 8b have mean values smaller than 0.2, and medians of 0.1 for maximum azimuth gaps as wide as 280 degrees. Inspection of Figs. 8c reveal that the inclusion of a larger number of stations in the magnitude estimates has neither a significant nor consistent impact in the reduction of the magnitude offsets.

Due to its weight as one of the main parameters determining the tsunami generating potential of a seismic event, we present the actual magnitude offsets for earthquakes with 6.5 or larger magnitudes in Fig. 9. The average absolute magnitude offsets for both TWCs still remain under 0.2 magnitude units. For events with GCMT moment magnitudes 7.9 and above, however, the Mwp method underestimates the magnitudes by as much as 0.5 magnitude units. Underestimations of the magnitude by a whole magnitude unit (-1.0) or more turn rare, but have in fact occurred. In spite of the large magnitude underestimations incurred for pathologically complex events such as the 24 December 2004, Sumatra, or the 11 March 2011, Japan events shown in Fig. 9, however, Fig. 7 demonstrates that the Mwp magnitude estimates still provided sufficient information to readily issue an expanding tsunami watch/warning within nine minutes of origin time. Moreover, we can state that despite the limitations highlighted above, application of the warning criteria listed in Table 1 led to the issuance of at least a regional tsunami warning for areas within 1000 km of the preliminary epicenter for all events whose actual GCMT moment magnitude crossed the 7.5 warning threshold.

Owing to the requirements of the Mwp method, not all stations contributing P-waves’ arrival times to the hypocenter determinations can actually provide a valid magnitude estimation. This means that after locating the earthquake’s epicenter the magnitude estimations turn into the main bottleneck slowing the issuance of a message product. How then have the TWCs gradually expedited their seismic analyses until making possible the issuance of obs messages and tsunami bulletins at average speeds of six and nine minutes, respectively?

Figure 10 illustrates how many earthquakes the TWCs characterized with magnitude averages calculated from different number of seismic stations from 2003 to 2011. As seen in Fig. 10a, b, c, d, e, f, and g, PTWC continued to wait for magnitude estimates from more than five seismic stations until the beginning of 2010. Figure 10k, l, m, n, o, p, and q, however, demonstrate that WCATWC started to issue more messages relying on magnitude estimates from no more than five seismic stations from 2006 onwards.

This trends appear strongly correlated with the

improvements in the message delay times seen in Figs. 5 and 6. Moreover, we can also correlate the gains in message speed at PTWC for 2010 and 2011 to a larger number of earthquake magnitudes computed from no more than five stations, as corroborated in Fig. 10h and i. Comparison with their WCATWC equivalent plots shown in Fig. 10r and s, makes obvious that while PTWC sent most messages containing magnitudes from five stations, WCATWC has the reverse pattern, sending most of their obs messages with no more than three or four stations in the magnitude averages. Figure 10j and t summarize the general trend through the years. It turns obvious that while PTWC kept waiting for magnitude averages from more than five, seven, or eleven stations before issuing its messages until 2010, WCATWC resorted more and more to just three and four station averages. This also means that PTWC can still improve its current message delay times by following a similar strategy without incurring any fundamental loss of accuracy in the magnitude estimates or compromising its tsunami warning responsibilities.

0-5 min Preliminary

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Gauge Analysis

Stations and Response Time

Sardina et al. 2011

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Becker et al. 2010

Seismic Analysis Steps 1

1.  Event detection 2.  Page to duty

scientists 3.  Pick review 4.  Locate/relocate 5.  MwP review 6.  Send PDL and

observatory message

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Initial Tsunami Message

0-5 min Preliminary

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EQ

>100km, inland,

or M6.5-7.0

Information Statement

M 7.1-7.5

<300 km

away

Marine Threat (local)


M 7.6-7.8

<1000 km

away

Coastal Threat (region)


M >= 7.9

<3 hr away

Major Threat (basin)


Y

Y

Y

Y

Y

Y

Y

N

N

N

N

N

N

Initial tsunami messages are based on earthquake information and expected tsunami travel times only.

Domestic:

Warning <3hr Watch 3-6hr

0-5 min Preliminary

Seismic Analysis

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Message Example

IOC Technical Series, 105 page 18

IOC

Technical Series, 105 Page 18

APPENDIX II. EXAMPLES OF PTWC NEW ENHANCED PRODUCTS FOR THE PTWS

A. Tsunami Information Statement (no tsunami threat)

a. Initial Product (text only)

i. Text Product

ZCZC WEPA42 PHEB 010008 TIBPAC TSUNAMI INFORMATION STATEMENT NUMBER 1 NWS PACIFIC TSUNAMI WARNING CENTER EWA BEACH HI 0008 UTC WED OCT 1 2014 ...TSUNAMI INFORMATION STATEMENT... **** NOTICE **** NOTICE **** NOTICE **** NOTICE **** NOTICE ***** THIS STATEMENT IS ISSUED FOR INFORMATION ONLY IN SUPPORT OF THE UNESCO/IOC PACIFIC TSUNAMI WARNING AND MITIGATION SYSTEM AND IS MEANT FOR NATIONAL AUTHORITIES IN EACH COUNTRY OF THAT SYSTEM. NATIONAL AUTHORITIES WILL DETERMINE THE APPROPRIATE LEVEL OF ALERT FOR EACH COUNTRY AND MAY ISSUE ADDITIONAL OR MORE REFINED INFORMATION. **** NOTICE **** NOTICE **** NOTICE **** NOTICE **** NOTICE ***** PRELIMINARY EARTHQUAKE PARAMETERS --------------------------------- * MAGNITUDE 6.7 * ORIGIN TIME 0000 UTC OCT 1 2014 * COORDINATES 20.0 SOUTH 173.4 WEST * DEPTH 178 KM / 111 MILES * LOCATION TONGA EVALUATION ---------- * AN EARTHQUAKE WITH A PRELIMINARY MAGNITUDE OF 6.7 OCCURRED IN THE TONGA ISLANDS AT 0000 UTC ON WEDNESDAY OCTOBER 1 2014. * BASED ON ALL AVAILABLE DATA... THERE IS NO TSUNAMI THREAT FROM THIS EARTHQUAKE. RECOMMENDED ACTIONS ------------------- * NO ACTION IS REQUIRED. NEXT UPDATE AND ADDITIONAL INFORMATION -------------------------------------- * THIS WILL BE THE ONLY STATEMENT ISSUED FOR THIS EVENT UNLESS ADDITIONAL DATA ARE RECEIVED OR THE SITUATION CHANGES. * AUTHORITATIVE INFORMATION ABOUT THE EARTHQUAKE FROM THE U.S. GEOLOGICAL SURVEY CAN BE FOUND ON THE INTERNET AT EARTHQUAKE.USGS.GOV/EARTHQUAKES -ALL IN LOWER CASE-. * FURTHER INFORMATION ABOUT THIS EVENT MAY BE FOUND AT PTWC.WEATHER.GOV AND AT WWW.TSUNAMI.GOV.

* COASTAL REGIONS OF HAWAII... AMERICAN SAMOA... GUAM... AND

▶  Header ▶  Headline ▶  Target Area ▶  Preliminary Earthquake

Parameters ▶  Evaluation ▶  Recommended Actions ▶  Potential Impacts ▶  Additional Information

•  Tsunami Forecasts •  Tsunami Observations

Message Dissemination

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AFTN

airports

GTS/NMC

international

NWW

USA & Canada

Web, RSS public

HAWAS

Hawaii NAWAS

USA & Canada

Telephone

warning points

FAX

warning points

Soc. Media

public

Email public

PDL USGS, public

EMWIN

warning points

SMS

RANET

Text Phone

Internet

TEX & CAP public

Seismic Analysis Steps 2

1.  Event detection 2.  Page to duty

scientists 3.  Pick review 4.  Locate/relocate 5.  MwP review 6.  Send PDL, Obs msg 7.  Revise Location 8.  Mm, Mw 9.  Theta 10.  W-phase CMT

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33 min - 2 hr Sea level gauge

monitoring

Tsunami Forecast Analysis

Run forecast model with W-phase CMT or other earthquake source as input. Calculate coastal threats and prepare to issue message update.

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GCMT W-phase

Subsequent tsunami messages are based primarily on tsunami forecasts.

Suppl. Tsunami Messages

CMT

>100km, inland, or M6.5-7.0


M >= 7.1

forecast <0.3 m


forecast 0.3-1 m

Marine Threat (local)

forecast 1-3m

Coastal Threat (region)

forecast >3m

Major Threat (basin)

Y

Y

Y

Y

Y

Y N

N

N

N

Domestic:

Advisory <3hr Watch 3-6hr Domestic:

Warning <3hr Watch 3-6hr

0-5 min Preliminary

Seismic Analysis

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Tsunami Message

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Seismic Analysis



Tsunami Message


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Issue Enhanced Products

0-5 min Preliminary

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To Public: ▶  Text bulletin

To Tsunami Warning Focal Points: ▶  Deep-Ocean Tsunami Amplitude

Forecast Map

▶  Coastal Tsunami Amplitude Forecast Map

▶  Coastal Tsunami Amplitude Forecast Polygon Map

▶  Coastal Tsunami Amplitude Forecast KMZ

▶  Table of Forecast Statistics for Regional Polygons

IOC Technical Series, 105

page i

Intergovernmental Oceanographic Commission Technical Series 105

User’s Guide for the Pacific Tsunami Warning Center Enhanced Products for the Pacific Tsunami Warning System August 2014

UNESCO

http://ptws-ptwcnewproducts.info

Deep-Ocean Forecast

▶  Tsunami Travel Time contours (assumes point source)

▶  Color range scaled so red / white show maxima

▶  Shaded textures show bathymetry

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Coastal Forecast

▶  Green’s Law used to propagate deep-ocean forecast to coast

▶  Tsunami Travel Time contours (assumes point source)

▶  Tsunami Wave Amplitudes at designated coastal forecast points

▶  Shaded textures show energy distribution

▶  Regional plots too:

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Coastal Forecast Polygons

▶  Threat level for designated forecast zones

▶  Color range scaled to match threat levels

▶  Grey textures show bathymetry

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Google Earth: User can zoom into areas of interest and click for detailed point forecast.

Forecast Statistics Table

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Max, Mean, Median, Standard deviation of coastal and deep-ocean (offshore) forecasts.

PTWC TABLE OF FORECAST STATISTICS FOR REGIONAL POLYGONS - RUN ID 20140816233614(for internal use only - not for distribution) Earthquake - Origin: 10/01/2014 00:00:00 UTC Coordinates: 45.2N 151.3E Depth: 028km Magnitude: 8.6 This table is issued for information only in support the UNESCO/IOC Pacific Tsunami Warning and Mitigation System and ismeant for national authorities in each country of that system. National authorities will determine the appropriatelevel of alert for each country and may issue additional or more refined information. Actual amplitudes at the coast may vary from forecast amplitudes due to uncertainties in the forecast and localfeatures. In particular, maximum tsunami amplitudes on atolls will likely be much smaller than the forecast indicates. Coastal Forecast (meters) Offshore Forecast (meters) Total Region_Name Maximum Mean Median STD Maximum Mean Median STD PointsUrup_Etorofu_Kunashiri_Shikotan_and_Habomai_Islands 20. 5.46 3.25 4.55 13. 2.55 1.84 2.49 101 Kuril_Islands 13. 3.37 2.44 2.67 5.9 1.43 1.10 1.07 95 Wake_Island 5.8 5.77 5.84 0.09 0.97 0.93 0.90 0.03 3 Society_Islands 4.4 2.24 1.89 0.88 1.8 0.57 0.48 0.33 35 Midway_Island 3.3 2.32 1.82 0.72 1.9 1.33 1.04 0.41 3 Northwestern_Hawaiian_Islands 3.1 2.07 1.98 0.58 1.4 0.90 0.99 0.41 5 East_Coast_of_Japanese_Main_Islands 3.0 1.37 1.21 0.39 3.0 0.86 0.70 0.48 407 Marshall_Islands 2.9 2.31 2.14 0.36 1.6 0.81 0.62 0.53 4 Bougainville_Papua_New_Guinea 2.9 1.49 1.09 0.82 2.0 0.74 0.60 0.43 75 Hawaii 2.8 1.27 1.21 0.40 1.4 0.45 0.42 0.20 147 Cook_Islands 2.7 1.64 1.35 0.78 0.35 0.22 0.20 0.09 3 Kosrae_State_Micronesia 2.7 2.69 2.69 0.00 0.34 0.34 0.34 0.00 1 West_Coast_of_Japanese_Main_Islands 2.7 0.56 0.20 0.70 2.1 0.34 0.12 0.42 465 Phoenix_Islands_Kiribati 2.6 2.61 2.61 0.00 0.61 0.61 0.61 0.00 1 Line_Islands_Kiribati 2.5 1.46 1.09 0.74 0.90 0.39 0.15 0.36 3 Choisel_to_Philip_Solomon_Islands 2.5 0.99 0.76 0.51 1.6 0.44 0.35 0.29 339 Sea_of_Okhotsk_Coast_of_Sakhalin_Russia 2.3 1.71 1.71 0.36 2.0 1.21 1.19 0.23 150

Sea Level Gauge Analysis

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Seismic Analysis

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Gauge Analysis

>600 stations from GLOSS,

NOAA, etc.

Deep-Ocean Coastal

Sea Level Gauge Analysis

0-5 min Preliminary

Seismic Analysis

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10-20 min Continued

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first arrival time

wave amplitude

wave period can downgrade from warning to advisory

Learning Check

1.  What are the two main types of data that PTWC uses? 2.  What is the primary criterion that determines PTWC’s

response time? 3.  What tsunami forecast level is considered potentially

damaging?

58

Tsunamis in Hawaii

Hawaii’s Tsunami History

Thirteen (13) significant tsunami events in Hawaii from 1819 to 2011.

More people are killed in Hawaii by tsunamis than any other natural disaster.

Tsunami deaths 1900-1998:

•  221 people (159 from 1946 event)

• Compare to only 7 Hurricane deaths during that same time.

60

“Kaha aku la ka nalu o ku‘u ‘āina.” (The surf of my land has swept everything away.) - Ancient Hawaiian proverb

Tsunamis Affecting Hawaii

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Major Tsunamis in Hawaii: 1 April 1946 – Alaska (M 8.6) 22 May 1960 – Chile (M 9.5) Travel Times to Hawaii: Local – minutes Alaska – 5 hours Japan – 7 hours S. Pacific – 7 hours Chile – 14 hours

Distant vs. Local Tsunamis

Distant Tsunami • A tsunami originating from a

far away source (> 620 miles or 1000 km away).

• Arrival of first wave expected within hours.

• Most tsunamis in Hawaii are distant.

Local Tsunami • A tsunami originating from a

nearby source (< 62 miles or 100 km away).

• Arrival of first wave expected within minutes.

• Danger is greater due to the limited warning time.

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April 1, 1946 – Distant Tsunami

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Source: M 8.6 earthquake in Alaska. Deaths: 159 people Damage: $26 million ($300 million today) Max Runup: 54 feet at Molokai (30 feet at Hilo)

Tsunami – Hilo, Hawaii April 1, 1946

November 29, 1975 – Local Tsunami

Source: M 7.7 earthquake 2 miles offshore of Wahaula Heiau near Kalapana •  Also caused 10 foot submarine

landslide

Deaths: 2 people (19 injured)

Damage: $1.4 million ($5.6 million today)

Max Runup: 47 feet at Keauhou

•  Wave first hit Halape 30 seconds after earthquake (26 feet runup at Halape)

Second most destructive tsunami to be recorded in Hawaii.

Tsunami – Kalapana, Hawaii November 29, 1975

Tsunami Warning Roles in Hawaii

Pacific Tsunami Warning Center

•  issues bulletin, watch, advisory, and warning information.

Hawaii Emergency Management Agency • makes decisions regarding public

safety and evacuation. Emergency responders • provides guidance to the public and

manage evacuation activities.

YOU • Heed official guidance. Activate

your personal disaster plan. Understand the different levels of warning information.

When you receive a tsunami alert…

Distant Tsunami Travel Times: Local Tsunami Travel Times:

Hawaii Island Imminent Maui ~15 minutes Oahu ~27 minutes Kauai ~45 minutes

Alaska 5 hours Japan 7 hours S. Pacific 7 hours Chile 14 hours

This makes a big difference!

Ask, “Is it distant or local?”

Response to a Distant Warning

Sirens will sound 3 hours, 2 hours, 1 hour, and 30 minutes prior to first wave arrival. Turn on your NOAA Weather Radio, commercial radio, or TV for information. Evacuate if you are in an evacuation zone or low-lying coastal area. Walking may be faster than driving. Stay off the roads if you do not have to evacuate. Vertically evacuate if you are in a concrete-reinforced high rise building (4th floor or higher). Do not return to to coast until advised by government officials.

Waves arrive within hours…

Don’t let this be you.

Response to a Local Warning

If you are at the beach or in a low lying area, and you feel the ground shake or see the water recede unusually – evacuate to high ground immediately! A tsunami generated by an earthquake off the Island of Hawaii may reach Oahu in less than 27 minutes! Walk, don’t drive! Stay off the roads if you do not have to evacuate. Vertically evacuate if you are in a concrete-reinforced high rise building (4th floor or higher). Do not return to to coast until advised by government officials.

Waves arrive within minutes…

Know your evacuation route.

Tsunami Safety Tips

•  If you are near the beach and feel strong earthquake shaking, that is your warning. Head to higher ground. §  Walking mauka for 15-20 minutes or going to the 4th floor of a strong

building is usually sufficient. Do not drive! • An unusual draining of the sea is a natural tsunami warning

sign, although this doesnʼ’t happen in every tsunami situation. • A tsunami is a series of waves, and the first wave may not be

the biggest. §  Since the time between waves is 5-60 minutes, the danger can last

for several hours. Be prepared with food, water, and a radio. •  Tsunami waves wrap around islands, so all coastlines are at

risk. •  If a warning is issued, follow instructions.

§  Local warnings (for tsunamis generated in Hawaii) require immediate action, but warnings from distant events are less urgent.

•  If you are in a boat at sea, make sure you’re in deep water and stay there. Bays and harbors, however, are dangerous places.

Learning Check

1.  What is the most common type of tsunami that affects Hawaii?

2.  What is the most urgent type of tsunami that affects Hawaii?

3.  When was Hawaii’s most deadly tsunami, and where did it originate?

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Mahalo!

Brian Shiro

[email protected]

NOAA Pacific Tsunami Warning Center

1845 Wasp Blvd, Bldg 176 Honolulu, Hawaii 96818

Extra Slides

RIFT Model Assumptions

RIFT = Real-time Inundation Forecast of Tsunamis model RIFT uses Green’s Law, which assumes: • Acoast = Aoffshore * (Doffshore / Dcoast)1/4

• Coastline is linear and exposed to open ocean. • Tsunami waves near coast are 1-D plane waves. • No significant wave reflections • No significant dissipation by turbulence • Bathymetry varies slowly compared with tsunami

wavelength. • Cliff boundary condition (coast is a vertical wall).

Wang et al. 2012

Limitations of RIFT model

Some caveats of RIFT include: • Initial results can vary by a factor of 2 due to

uncertainties in magnitude, depth, and assumed mechanism of earthquake. Later results contrained by Wphase are more reliable.

• Green’s Law can overestimate coastal amplitude for small islands (< 30 km size).

• Green’s Law can underestimate wave amplitude in resonant harbors.

• Coastal amplitude forecast is not necessarily indicative of inundation depth, which is a function of local topography.

Wang et al. 2012

pacific tsunami warning center: introduction to tsunamis and ptwc operations

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