HR: 11:20h
AN: G12A-05    [Abstracts]
TI: Relative plates Motions and associated deformation across the Sunda-Sumatra-Arakan trenches
AU: * Socquet, A
EM: socquet@ipgp.jussieu.fr
AF: IPGP, 4 pl jussieu, paris, 75005, France
AU: Vigny, C
EM: vigny@geologie.ens.fr
AF: ENS, 24 rue lhomond, paris, 75005, France
AU: simons, w
EM: Wim.Simons@lr.tudelft.nl
AF: DEOS-DUT, Kluyverweg 1, delft, 2622LR, Netherlands
AU: Pietrzack, J
EM: J.D.Pietrzak@tudelft.nl
AF: citg-dut, stevinweg 1, delft, 2628CN, Netherlands
AU: ham, d
EM: David.Ham@imperial.ac.uk
AF: ESE-imperial college, imperial college, london, SW72AZ, United Kingdom
AU: cattin, r
EM: cattin@geologie.ens.fr
AF: ENS, 24 rue lhomond, paris, 75005, France
AB: Using a regional GPS data set, we assess the relative motion between the Indian, Australian and Sundaland plates and discuss the deformation taking place between them from the Sumatran trench to Myanmar. Our results confirm that the current motion of India is slower than predicted by the NUVEL-1A model, and in addition our India-Eurasia motion is significantly (5 mm/yr) slower than previous geodetic determinations. This new Indian motion, combined with a refined determination of the Sunda plate motion, predicts a relative motion of 35 mm/yr oriented N10 at the latitude of Myanmar, and 35 mm/yr oriented 17° at the latitude of the Andaman Basin. The relative motion between Australia and Sunda however is much faster and reaches 53mm/yr oriented N9° at the latitude of northern Sumatra. In Myanmar, the Sagaing Fault accommodates 18 mm/yr, representing only half of the shear component of the motion. The remaining deformation (23 mm/yr) is likely accommodated elastically on the Arakan oblique subduction, which could produce a major earthquake every few hundred years. At the latitude of Sumatra, interseismic deformation extended ~400km below Sumatra and the Malaysian peninsula within the Sunda plate, attesting for a deeply locked subduction zone before the earthquake. We analyse the deformation associated with the 2004 earthquake that broke the Sumatra-Andaman trench. Tsunami modelling, validated against independent Jason-1 altimetry data and tsunami arrival time data, was used to retrieve the most likely co-seismic slip distribution based on geodetic data inversions. Coulomb stress increase computations show unclamping associated to right lateral increased shear stress on the Sumatra fault, north of the equator. On the trench, coulomb stress is increased at both ends of the rupture, on the Sumatra trench south of the equator, and the Arakan trench to the north.
DE: 1209 Tectonic deformation (6924)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 8123 Dynamics: seismotectonics
DE: 9320 Asia
SC: Geodesy [G]
MN: 2007 Fall Meeting