HR: 11:05h
AN: G12A-04    [Abstracts]
TI: The Sundaland Block in SE Asia: A Tectonic Entity Surrounded by Earthquake Hazards
AU: * Simons, W J
EM: Wim.Simons@lr.tudelft.nl
AF: DEOS/DUT, Kluyverweg 1, Delft, NL-2622 LR, Netherlands
AU: Vigny, C
AF: ENS, 24 rue Lhomond, Paris, 75231, France
AU: Socquet, A
AF: IPGP, Place Jussieu, Paris, 75005, France
AU: Ambrosius, B A
EM: B.A.C.Ambrosius@tudelft.nl
AF: DEOS/DUT, Kluyverweg 1, Delft, NL-2622 LR, Netherlands
AU: Team, S
EM: M.C. Naeije@tudelft.nl
AF: AUNP Office, Chulalongkorn University, Bangkok, 10330, Thailand
AB: The present-day crustal deformation of SE Asia results from the convergent motion between the Sundaland (SU) block, which covers most of SE Asia, and the adjacent Philippine (PH), Australian (AU) and Indian (IN) tectonic plates in highly active subduction zones. To the north, SU is disconnected from the ‘stable' Eurasian (EU) plate by the IN-EU collision which shaped the crustal deformation zones in and around the Himalayan Region. The oblique relative motion between IN/AU and SU caused the 2004 Sumatra-Andaman earthquake/tsunami disaster.
A unique (100+ points) GPS velocity field (in ITRF2000 and ITRF2005) that spans the entire SE Asia region, based on a decade of regional measurements (1994-2004), was exploited to resolve Sundaland's motion and boundaries and perform a detailed study of the inter-seismic intraplate deformation [1]. This revealed previously undetected deformation patterns on Java, North Borneo and North Thailand and the much larger subduction deformation zone extending (>600 ~km) from the Sumatra trench towards Peninsular Malaysia and South Thailand. There far-field data implies a ~220~km wide locked trench fault plane below SU at shallow (≤gslant 13°) dip angle and full coupling on the subduction. This matches the very large magnitude of the 26/12/2004 earthquake and the subsequently recorded wide-spread co-seismic deformations throughout the network also provided the first unambiguous evidence of the rupture plane length [2].
The post-seismic motions (both at spatial and temporal scales) of ~50 GPS sites (2005-2006) provide information on the contribution of various mechanisms (aftershocks/afterslip, visco-elastic relaxation and poro- elasticity). These post-seismic motions are very significant in the far-field, e.g. the island of Phuket additionally moved ~1.5 times the initial 2004 and 2005 co-seismic displacements. References:
[1] Simons, W.J.F, et al al.(2007), J .Geophys. Res., 112, B06420, doi:10.1029/2005JB003868.
[2] Vigny, C. et al.(2005), Nature, 436, 201-206, doi: 10.1038/nature03937
UR: http://www.deos.tudelft.nl/~wims/sunda.html
DE: 1243 Space geodetic surveys
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 8158 Plate motions: present and recent (3040)
DE: 9320 Asia
SC: Geodesy [G]
MN: 2007 Fall Meeting