tectonic setting indonesia dan pemodelan gempa dan tsunami · indonesia kaya sda dan bencana •...
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Tectonic Setting Indonesia dan Pemodelan gempa dan Tsunami
Danny Hilman Natawidjaja
Geoteknologi LIPI
Pelatihan Pemodelan Tsunami Run-up, RISTEK, 20 Agustus, 2007
Indonesia kaya SDA dan bencana
• Gempabumi• Tsunami
• Letusan gunung api• Longsor• Banjir
• Angin topan• Badai
• Kebakaran hutan alam, dll.
Danny H. Natawidjaja – RUTI 2005
Mitigating Earthquake and Tsunami
• What?• Where ?• How big ?• When?
• Surface faulting• Shaking • Tsunami• Landslides• liquefaction
SOURCE HAZARDS
Banyak disepelekan!
PHYSICALMODELING
Model Tsunami (Run-up) yang baik• Input data sumber gempa/tsunami yang dapat
dipertanggung jawabkan• Pemilihan scenario parameter sumber yang
masuk akal secara ilmiah
• Data bathimetri dan topografi serta tutupanlahan yang se-akurat mungkin
• Mengerti keterbatasan pemodelan tsunami, baikkarena simplifikasi matematis dari proses alamjuga karena asumsi-asumsi yang dipakai yang disebabkan ketidaktahuan data sumber yang sebenarnya
60 – 50mm/year
PARAMETER UTAMA SUMBER
• geometri sumber: panjang-lebar, lokasi
• arah dan besar pergerakan
• pengangkatan dan penurunan muka bumi
• arah rupture dan cepatnya pergerakan
PARAMETER DASAR:
• Bathimetri
• topografi (utk run-up modeling)
DATA CONSTRAINTS ON TSUNAMI MODEL
PARAMETER SEKUNDER:
• Cabang patahan di dekat palung
• longsoran di bawah laut
Indonesia is an earthquake country : Crustal motions from GPS (Bock et al, 2004)
India-Australian Plate
Eurasian Plate
Pacific Plate
5-6 cm/yr
12 cm/yr
Earthquake in Indonesia since 1964
Megathrust earthquake
Forearc islandstrench
Moho
ZONA SUBDUKSI
Interseismic period(slow strain accumulation)
Slow uplift
Slow Submergence
It is like a spring board!
Co-seismic = earthquake(sudden strain release)
Sudden Uplift
It is like a spring board!
Co-seismic = earthquake(sudden strain release)
Initial Tsunami Formation
Locking zone(=seismic zone= zone of strain accum.)
Depth<60km
Tsunami modelingTsunami modeling
SOURCEFault parameters
Wave-propagation: F(depth)
Shoreline interactionBathi & topo detil
Epicenter data of Aceh earthquake 2004 – 1 day after
Preliminerary Rupture Source Model of Dec 2004 Aceh EarthquakeChen JI - Caltech
Max. slip 20m
M 8.9
The early model of Aceh Tsunami 2004 (Steve Ward)
(Tsunami Research GroupMarine Research Center ITB)
Tsunami source base on the Altimetry Data
ANIMATION of The 2004 Aceh tsunami(Hamzah Latief)
Vertical displacement of seafloor estimated by Hirata et al. [2005] from satellite altimetry data.
ChenJi
Ward
We have used
GPS
records of sea-level change in corals
and satellite imagery
To understand the behavior of the tsunami source
METHODS OF STUDYING THE SOURCE
Model G Mw9.2
Based on:• Coral Sateliteimagery analysis
• GPS campaign mode
• Continuous GPS (far field)
Rupture:• ~1600km long• 10 – 30 meterDisplacementwestward
(after Chlieh et al, 2005 and Subarya et al, Nature, March 2006)
Courtesy of Mohamed Chlieh
Uplift in 2004
• The greatest uplift occurred west of the Nicobar islands and southwest of Aceh
Source parameters
Of
Aceh Tsunami 2004
Mengenal sumber gempa-tsunami Indonesia
Gempa Sumatra(yg paling banyak dipelajari)
Megathrust earthquake
Forearc islandstrench
Moho
Sumatran Fault Zone
Sumatran earthquake(the most well understood)
Sumatran fault Zone
INDIAN-AUSTRALIANPLATE
EURASIAN PLATE
50 – 60 mm/yearPlate
movement
Jakarta
1881 (7.9)
1941 (7.9)
1797 (M8.4)
1861 (M~8.5)
1907 (~M7.8)
1935 (M7.7)
2000 (M7.8)
2002
1833 (8.9)
2004 (M9.15)
2005 (M 8.7) Currently locked,Near end of cyclesection
Un known section,No large eartquakes inHistorical records
Malaysia
Briggs et al., Science, 2006
the 2004 earthquake
the 2005 earthquake
SIMELUE ISLAND
1861uplifttsunami
1799uplift
1400
965
Similar to dates of uplifted coral and subsided mangrove in the Andaman islands (Rajendran et al 2007) Similar to dates of uplifted coral terrace in the Andaman islands and possible tsunami deposit on east coast of India (Rajendran et al 2007)
uplift
uplift
Paleoseismic history Simeulue island
SIMELUE ISLAND
1861uplifttsunami
1799uplift
1400
965
uplift
uplift
Paleoseismic history Simeulue island
NW: 400 to 600 year recurrence?
SE: 140 to 200 year recurrence?
SE Simelue:
NW Simelue:
Drawn beach north of Calang, Aceh area, July 2007
Paleotsunami study in Banda Aceh area, July 2007
Batee
fault
A tear in the over-riding plate?
March 28,2005
Slip on the megathrust
Batee
fault
Rupture/sumber gempa
Model sumber gempa di zona subduksi
A A’
uplift subsidence
hingeline
Rupture zone
A A’
uplift subsidence
hingeline
Rupture zone
Near Afulu village, west coast of Nias island
January 2005
May 2005
Examples from Nias, Simeulue and the Banyak islands
The March 2005 event resulted in impressive uplift …
Old high tide
Old low tide
Old high tide
New high tide
Haloban village, Banyakislands
… dan wilayah di timurnya turun
A Historical sketch of the 1861 earthquake in Nias
But, how about big tsunami in 1861 Nias earthquake?
March 28,2005
Slip on the megathrust
Batee
fault
1861?
SegmenMentawai !!!
DimanaSelanjutnya?
Stress Shadow dan Efek pemicuan gempabumi (Mc Closkey)
Coastlines show subsidence of the
Mentawais for many decades
Evidence for giant earthquakes in 1797 and 1833
Evidence for giant earthquakes in 1797 and 1833
Fossil microatolls in the intertidal zone, east coast of North Pagai island
In Mentawai Island
Years (AD)
~1370 ~1600 1797 & 1833 Paleogeodetic
For ~700 years
The Mentawai
patch appears to
be time-predictable
and near failure
Ele
vatio
n re
lativ
e to
mod
ern
sea
leve
l (c
m)
SEISMIC
GAP:Before Aceh-Andaman Earthquake
Malaysia
Sumatra
SEISMIC
GAP:After Aceh–Andaman Earthquake
Before NiasEarthquakeMalaysia
Sumatra
SEISMIC
GAP:After NiasEarthquake
Is
MentawaiSeismic gapMalaysia
Sumatra How aboutJawa ??
SuGArVelocity FieldUp to June 2006
OngoingPost-slip
OngoingSqueezingOf Mentawai
These locked patches are the likely source of the next great Mentawaiearthquake and tsunami
This locked patch broke in 2005
Chlieh et al (in review) J Geophys Res
Photo: Jose Borrero
Padang now (~800,000 people)
Padang in 1797 (~4,000 people)
Earthquake and Tsunami Scenarios for Western part of Sumatra
Patterns of Uplift of the seafloor produced by the six megathrust ruptures scenarios (Borero et al, 2006)
1797 1833
Scenario1
Scenario2
Scenario3
Scenario4
D.H. Natawidjaja May 2007
Animasi proses deformasi gempa dan tsunami
Animasi proses deformasi gempa dan tsunami
Animasi proses deformasi gempa dan tsunami
Surutdulu
Surutdulu
TidakSurutdulu
Tsunami simulation for an Aceh-2004-like source
Scenario 3: Uplift from 20 m slip on 700-km megathrust rupture(Borero et al, 2006)
20-m Slip Scenario in PadangD.H. Natawidjaja May 2007
10-m Slip Scenario in Padang
20-m Slip Scenario in BengkuluD.H. Natawidjaja May 2007
10-m scenario
20-m scenario
20-m scenarioTurun 0.5 meter
10-m scenario
20-m scenario
20-m scenarioTurun 1.5 meter
Sumber Gempa - Tsunami Jawa(sedikit tahu, banyak tidaknya)
SUMARY OF JAVA EARTHQUAKE 1840 – 2005(modified from Newcomb and McCann, 1987)
• Very old subducted oceanic crust (~150 million years old)•Less-frequent earthquakes and no M≥8 EQ in the history• But what did not happen does not mean would not happen
1994 (Pancer)
Tim
e
M 7.82006 tsunami M7.8)
Seismic record for the past 30 years
It lead to a big question…What is the maximum magnitude of earthquake of the Jawa Subduction zone?
July 2006 (Mw 7.8)
1994 (Mw 7.8)
SEISMIC GAP
Is it actually less than M8?How about in a much longer time??
M 7.8
Bagaimana memilih tsunami sourceYang tepat untuk Selatan Jawa???
M 7.8
Bagaimana memilih tsunami sourceYang tepat untuk Selatan Jawa???
M 7.8
Bagaimana memilih tsunami sourceYang tepat untuk Selatan Jawa???
M 9.0
Bagaimana memilih tsunami sourceYang tepat untuk Selatan Jawa???
M 9.0
Bagaimana memilih tsunami sourceYang tepat untuk Selatan Jawa???
Historical On-land Earthquakes of Jawa(Natawidjaja, 2006)
D.H. Natawidjaja May 2007
Gempa Jakarta 1699
Gempa Jakarta !!!Hikayat Jakarta / Willard A. Hanna. Yayasan Obor Indonesia. 1988 Ed. 1 ISBN 979-461019-4Pada akhir abad ke-18, citra Ratu Timur itu menurun drastis. Willard A. Hanna (Hikayat Jakarta) mencatat, bahwa kejadian itu diawali oleh gempa bumi yang bukan main dahsyatnya, malam tanggal 4 dan 5 November 1699, yang menyebabkan kerusakan besar pada gedung-gedung dan mengacaukan persediaan air dan memporak-porandakan sistem pengaliran air di seluruh daerah. Gempa itu disertai letusan-letusan gunung api dan hujan abu yang tebal, yang menyebabkan terusan-terusan menjadi penuh lumpur. Aliran sungai Ciliwung berubah dan membawa sekian banyak endapan ke tempat dimana sungai itu mengalir ke laut, sehingga kastil yang semula berbatasan dengan laut, seakan-akan mundur sedikit-dikitnya 1 kilometer ke arah pedalaman. ………
Gempa-Tsunami di Indonesia Timur
(sumber-nya paling potensial tapi sangat kurang dipelajari)
Earthquake and Tsunami of East Indonesia Region
Active Tectonics
Earthquake and Tsunami of East Indonesia Region
Active Tectonics
Earthquake and Tsunami of East Indonesia Region
Earthquakes M>5: 1964-2006 (Engdahl, 2006) < 30 km depth
30 - 60 km
D.H. Natawidjaja May 2007
Earthquake and Tsunami of East Indonesia Region
Recent Earthquake Mw > 7 since 1973D.H. Natawidjaja May 2007
Earthquake and Tsunami of East Indonesia Region
Historical Earthquake since 1600 (USGS)D.H. Natawidjaja May 2007
Earthquake and Tsunami of East Indonesia Region
Tsunamigenic earthquake zones andHistorical Tsunami
D.H. Natawidjaja May 2007
Earthquake and Tsunami of East Indonesia Region
Historical Tsunami: Year (Run-up in m)
Tsunami database from H.Latief
Earthquake and Tsunami of East Indonesia Region
Historical Tsunami: Year (death)
Tsunami database from H.Latief
Bagaimana dengan tsunami source untuk wilayah Maluku?
M 8.0
Bagaimana dengan tsunami source untuk wilayah Maluku?
M 8.0
Bagaimana dengan tsunami source untuk wilayah Maluku?
M 8.0
Bagaimana dengan tsunami source untuk wilayah Maluku?
M 9
Data from URS
Probability map of tsunami-height hazards in Southeast Asia
Anda percaya ??? Bagaimana kualitas data sumber yang digunakan?
Paul Sommervile &Hng Kie Thio(URS)
Hanya memakaiData seismic daritahun 1973??
Concluding remarks
Knowledge ofEarthquake and Tsunami
Sources,
Designing Observation Network
and System forResearch and
Early Warning System
Public Education and
Community Preparedness
Infrastructure changes, Evacuation plan, andPost-Disaster actions
RESEARCH
HAZARD-RISK MODELS Tsunami modeling
Tunas kelapa yang tumbuh setelah gempa Maret 2005, P. Wunga,Nias, Juni 2006
Terima kasihTerima kasih