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Simeuleu island
The The AcehAceh/Andaman earthquake:/Andaman earthquake:
WhatWhat’’s next?s next?
Kerry Sieh
Tectonic Observatory, Caltech
11 March 2005
Indo-burmansource(s)
westSumatransources
Indian Ocean Sumatra
WEST EAST
Courtesy ofRobinLacassin,IPG Paris
What do we know about the2004 rupture?
WEST EAST
The pattern and magnitude of submergence anduplift constrain the rupture location and amount
Photo by Denis Giles
Camorta island, Nicobars
QuickBird 23 June 2004 QuickBird 28 December 2004
Banda Aceh
before after
Great Nicobar island
before after
Courtesy of Aron Meltzner,Tectonics Observatory,
Caltech
North Sentinel island, Andaman island group
before after
Courtesy of AronMeltzner, TO, Caltech
Just off the WWW,from Centre forEarth ScienceStudies, Trivandrum,India
http://www.seires.net/content/view/122/52/
GPS horizontaldisplacements
Simeuleuisland
Courtesy of Robin Lacassin,IPG Paris
2004
Helicopter crew
Boat crew
Science team Logistics and GPSDayat
Samsir
Man et al
Me
Danny Natawidjaja
John Galetzka
Imam Suprihanto
Bambang Suwargadi
MohamedChlieh
100 km
Simeulue island, Aceh, Sumatra
Annual lowest tide(“highest level ofsurvival” or “HLS”)
Substrate
Coral head
The coral “instrument”
130 cm
130 cm
155 cm
Submergence before the uplift
There must be an interesting story in here!!
From Danny Natawidjaja’s Ph.D. thesis,Tectonic Observatory, Caltech, 2003
Oops!
8 meters
15˚ dip
Trench to 43 kmdepth
First attempt to model theuplift, Mohamed Chlieh,Tectonics Observatory,Caltech
8 meters
15˚ dip
Trench to 43 kmdepth
2 segments
8 meters
15˚ dip
Trench to 43 kmdepth
2 segments
98 cm, 2004
5 cm, 2002
100 km
100 km
2004
19071861
1935
1797/1833
Submergence rates of thepast 50 years …
-1
… suggestthat the depthof locking ofthesubductioninterfacevaries alongstrike
-1
From MohamedChlieh, TO, Caltech
The wider thepatch, thebigger thepotentialearthquake?
To improve our measurements of deformation,we began installing the Sumatran GPS Array(SuGAr) in 2002
48
43
31
29
34 32
Mapping the great 2002 ruptureinspired many questions
Modeling of campaignand continuous GPSvelocity vectors alsosuggests that the depthof locking varies widelyalong strike
Mapping the great 2002 ruptureinspired many questions
Let’s take a look at thelonger term.
First here
Then here
Paleogeodetic records near the Equator show very-long-termchanges in vertical rates of deformation
~1380
~1605
17971833
To the south, we see repeating giantearthquakes
1833
18161808 1797
Two giant earthquakes and intermittent interseismic submergence
1797
90 cm
1797
Uniform 4 m slip Mw 8.2
1833
200 cm
1833
Uniform 10 m slip Mw 8.7
1833
Uniform 10 m slip Mw 8.7
1833
1797
1935
?
?
Smallerearthquakes,thinner lockedpatches.
Giantearthquake,thicker lockedpatches.
1797, M > 8.4
Recall that at some sites, upliftepisodes appear to be roughlyperiodic
An Indo-burmansource(s)
westSumatransources
Singapore
Jakarta
Kuala Lumpur
The past record of large megathrust events inNorth and West Sumatra suggests the nextevents are not too far off
Singapore
Jakarta
Kuala Lumpur
1797
Most of the megathrust failedbetween 1797 and 1907
Singapore
Jakarta
Kuala Lumpur
18331797
Most of the megathrust failedbetween 1797 and 1907
Singapore
Jakarta
Kuala Lumpur
18331797
1861
Most of the megathrust failedbetween 1797 and 1907
Singapore
Jakarta
Kuala Lumpur
18331797
18611907
Most of the megathrust failedbetween 1797 and 1907
Singapore
Jakarta
Kuala Lumpur
18331797
18611907
1935
A 70-km long patch failed in 1935,between the giant 1861 and 1833patches
Singapore
Jakarta
Kuala Lumpur
18331797
18611907
1935
A flurry of ruptures have occurredsince 2000
2000
2002
2004
Singapore
Jakarta
Kuala LumpurNext?
19071935
2000
2002
2004
Based upon what we have seen in the coral microatolls, I expect that we will seetransients in the months, years or decades between the 2004 Aceh/Andamanearthquake and the next west-Sumatran earthquakes. … the TO will be ready!
Thankyou
(My survivor buddiesaround a tsunami
block, Simeulueisland)
Coseismichorizontalvectors fromSuGAr (in mm).
Model
Data