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Crustal Deformation Associated with Crustal Deformation Associated with the Central Sumatran Earthquakes of the Central Sumatran Earthquakes of March 6, 2007, Derived from March 6, 2007, Derived from ALOS/PALSAR and GPS ALOS/PALSAR and GPS

Manabu Hashimoto, Takeshi Katagi (DPRI, Kyoto University) Yuichi Otsuka (STEL, Nagoya University)

PALSAR level 1.0 data are shared among

PIXEL, and provided from JAXA under cooperative research contract with ERI,

• Univ. Tokyo. The ownership of PALSAR

data belongs to METI (Ministry of Economy, Trade and Industry) and JAXA.

The Central Sumatra Earthquake The Central Sumatra Earthquake

• f March 6, 2007
• f March 6, 2007

Doublet of M6.4 and M6.3 Epicenters are closely located to the

Sumatra fault: A pull-apart basin

Focal mechanism of right lateral strike-slip Surface ruptures

Where did they occur? Where did they occur?

Central Sumatra Inland events on

the Sumatra fault

Sumatra fault:

right-lateral strike- slip fault accommodating

• blique subdution

Volcanic chain

Past Past Seismicity Seismicity

(Natawidjaja et al., 2007)

2 7 2 7

Surface Ruptures due to the Doublet of Surface Ruptures due to the Doublet of 2007 2007

(Natawidjaja et al., 2007) Surface rupture

1st event 2nd event

Offset 22cm Offset 24cm Ruptured the Sumani segment Ruptures the Sianok segment On the courtesy of Dr. Nakano

On the courtesy of Dr. Danny Hilman Natawidjaja

CGPS observation in CGPS observation in SE Asia SE Asia

11 sites in Thailand 3 sites in Indonesia 1 site each in Singapore and

Myanmar

Complex tectonics

– Oblique subduction – Back-arc spreading – Sumatra and Sagaing faults

Daily Coordinate Changes of the CGPS Sites in SE Asia Daily Coordinate Changes of the CGPS Sites in SE Asia (NS) (NS)

ITRF2000

Postseismic displacement following the Nias event at PDNG?

Daily Coordinate Changes of the CGPS Sites in SE Asia Daily Coordinate Changes of the CGPS Sites in SE Asia (EW) (EW)

Coordinate Changes at Coordinate Changes at Padang(PDNG Padang(PDNG) in 2007 ) in 2007

~3cm ~3cm ~1cm ~1cm

Close Close-

• up of Central

up of Central Sumatra Sumatra

Area of ALOS/PALSAR Image

• Strike

Strike-

• slip type

slip type

• NNW

NNW-

• SSE trending

SSE trending nodal plane is consistent nodal plane is consistent with the strike of Sumatra with the strike of Sumatra fault fault

• Vertical nodal plane

Vertical nodal plane

(USGS,2007) (USGS,2007)

AlOS AlOS/PALSAR Images /PALSAR Images

Master: October 15, 2006 Slave: June 6, 2007 Descending orbit Bperp=1510m

Fringe around the

source area

Discontinuities

parallel to the Sumatra fault

Low coherence in

mountains

Interferogram Interferogram

Fringe around the

source area

Discontinuities

parallel to the Sumatra fault

Low coherence in

mountains

Interferogram Interferogram

Unwrapped Image (Preliminary) and GPS Displacement Unwrapped Image (Preliminary) and GPS Displacement

Unwrapped Image (Preliminary) and GPS Displacement Unwrapped Image (Preliminary) and GPS Displacement

Theoretical Displacements for Two Segment Model Theoretical Displacements for Two Segment Model No conjugate fault

Fault Parameters Fault Parameters

L

(km)

W

(km)

H

(km)

δ

(deg)

φ

(deg)

λ

(deg)

D

(m)

Mo

(x1018 Nm)

Mw 30 20 0.5 78 148

• 175

0.4 7.2 6.5 35 20 0.5 78 148

• 175

0.3 6.3 6.5

According to the Matsuda According to the Matsuda’ ’s s Formula Formula・・・ ・・・

M=6.3~6.4 gives L=7.6~8.7km，D=0.8~0.9m. The central Sumatra earthquake

Unusually long fault length Inconsistent with the Matsuda’s formula Significant slow slip? Surface creep?

10 / 6 . / ) 9 . 2 (log L D L M = + =

Summary Summary

Discontinuities along the surface ruptures Fault length ~ 65km Fault length and slip are inconsistent with

Matsuda’s formula

Possible creep? No conjugate fault