HR: 0800h
AN: G11A-1199    [Abstracts]
TI: A Slip Model for the Mw 9.0 2004 Sumatra-Andaman Earthquake Based on GPS Measurements of Coseismic Displacement
AU: * Shuler, A E
EM: shulea@rpi.edu
AF: Rensselaer Polytechnic Institute, Department of Earth & Environmental Sciences 110 8th St., JSC 1W19, Troy, NY 12180 United States
AU: Freymueller, J
EM: jeff@giseis.alaska.edu
AF: University of Alaska Fairbanks, Geophysical Institute PO Box 757320, Fairbanks, AK 99775 United States
AU: Rajendran, C
EM: cp_r@cessind.org
AF: Centre for Earth Science Studies, P.B. No. 7520, Akkulam, Thiruvananthapuram, 695 031 India
AB: The Mw 9.0 Sumatra-Andaman Earthquake of 2004 caused widespread deformation throughout Asia. We present coseismic displacements for Asia - the result of network solutions from sixty continuous GPS sites throughout the region as well as five sites in the Andaman and Nicobar Islands which had periodic occupations. From these calculations, we created a seven-segment slip model with predicted horizontal displacement vectors in excellent agreement with observations from near-field sites. Slip in the earthquake extended from the northern coast of Sumatra to the northern boundary of the Andaman Islands. Our model had reduced slip in the southernmost part of the rupture zone, with increased slip in the northern half of the rupture zone and a patch of localized large slip near the Nicobar Islands. Convergence vectors were calculated for each fault segment. These indicate significantly different slip azimuths for the Sumatra and Andaman segments of the rupture, with a gradual rotation of the slip vector along the length of the rupture. The oceanic crust in this region is in a diffuse plate boundary between the Capricorn, Indian and Australian plates, and the rotation of the slip vectors is largely consistent with the change in motion of the oceanic plates across this diffuse boundary. In an effort to resolve the issue over whether there was significant slow aseismic slip in the northern part of the rupture zone, we evaluated the contribution of each fault segment to the displacement at each site. In our model, the northernmost segments produced only a small contribution to the total displacements of any medium- to far-field continuous GPS sites (such as Bangkok and Phuket, Thailand), and thus, it is difficult to rule out the possibility of slow slip based on kinematic solutions for these sites. However, our model and those kinematic solutions (Vigny et al., 2005) show that if slow slip was present, it had to be limited to the northernmost extreme of the rupture.
DE: 1209 Tectonic deformation (6924)
DE: 1299 General or miscellaneous (1709)
SC: Geodesy [G]
MN: Fall Meeting 2005