Tectonic Setting Indonesia dan Pemodelan gempa dan Tsunami · Indonesia kaya SDA dan bencana • Gempabumi • Tsunami • Letusan gunung api • Longsor • Banjir • Angin topan

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



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


M 7.8


M 9.0


M 9.0


Historical On-land Earthquakes of Jawa(Natawidjaja, 2006)


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


Active Tectonics


Earthquakes M>5: 1964-2006 (Engdahl, 2006) < 30 km depth

30 - 60 km



Recent Earthquake Mw > 7 since 1973D.H. Natawidjaja May 2007


Historical Earthquake since 1600 (USGS)D.H. Natawidjaja May 2007


Tsunamigenic earthquake zones andHistorical Tsunami



Historical Tsunami: Year (Run-up in m)

Tsunami database from H.Latief


Historical Tsunami: Year (death)

Tsunami database from H.Latief

Bagaimana dengan tsunami source untuk wilayah Maluku?

M 8.0


M 8.0


M 8.0


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

Tectonic Setting Indonesia dan Pemodelan gempa dan Tsunami · Indonesia kaya SDA dan bencana • Gempabumi • Tsunami • Letusan gunung api • Longsor • Banjir • Angin topan

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