HR: 09:30h
AN: U21C-06    [Abstracts]
TI: GPS Constrained Coseismic Slip of the 26 December 2004 Great Sumatra-Andaman Earthquake
AU: Wang, M
EM: mwang@gps.gov.cn
AF: Institute of Earthquake Science/CEA, 63 Fuxing Rd, Beijing, 100036 China
AU: * Shen, Z
EM: zshen@ies.ac.cn
AF: Institute of Geology/CEA, P.O.Box 9803, Qijiahuozi, Beijing, 100029 China
AU: Wan, Y
EM:
AF: School of Disaster Prevention Technology/CEA, Yanjiao, Hebei, 101601 China
AU: Zeng, Y
EM: zeng@usgs.gov
AF: US Geological Survey, 1711 Illinois Ave, Golden, CO 80401 United States
AB: The 26 December 2004 Sumatra-Andaman megathrust earthquake is one of the largest earthquakes ever recorded since 1900. The event took place at the Sumatra-Andaman subduction zone between the Australia and Sundaland plate in the south and the India and Burma plate in the north. Despite of its great size and catastrophic consequences, the magnitude and rupture distribution of the earthquake are still not well constrained yet. We ensemble a GPS data set from continuous and survey mode stations in the region to obtain the coseismic displacement field. The continuous data set includes these from the IGS stations located in East Asia and around the Northern Indian Ocean, from the Crustal Motion Observation Network of China in mainland China and South China Sea, and from Caltech's Indonesian GPS network in central Sumatra. Three months and ten days of data before and after the quake respectively are processed to derive the coseismic displacement offsets using the GAMIT and QOCA softwares. Three additional data sets of coseismic displacement offsets are also incorporated, one from the southeast Asia area (Vigny et al., 2005), another from the India subcontinent (Banerjee et al., 2005), and the third from the Andaman and Nicobar Islands (http://www.seires.net/content/view/122/52/). These data are used to invert for fault rupture which is devised as dislocation in a layered elastic media. We also adopt the `Earth flattening' method to accommodate the curvature effect of the Earth's surface, which is significant at the far field and should not be neglected. The fault model is composed of multiple tiles, meshing the interface of the subduction slab, with second order smoothing applied to enforce slip continuity. Our result shows dominant thrust faulting for all the patches, ranging from ~2.5 m to 7 m in amplitude, with the largest slip centered around the central section of the rupture zone 5°-10°N latitude. Rupture is also accompanied with meter level right slip for the central and north sections, and almost a meter left slip for the southern most segment respectively. The total seismic moment accumulated over the entire rupture plane is ~6.5×10²² N-m, equivalent to the energy release of an Mw9.2 earthquake.
DE: 1209 Tectonic deformation (6924)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 7215 Earthquake source observations (1240)
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 8118 Dynamics and mechanics of faulting (8004)
SC: Union [U]
MN: Fall Meeting 2005