HR: 1340h
AN: S43A-1039    [Abstracts]
TI: Using Earthquake Rupture Variations along the Sumatra-Andaman Subduction System to Examine Fault Zone Variations
AU: * Bilek, S L
EM: sbilek@nmt.edu
AF: Earth and Environmental Science Dept., New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801 United States
AB: The 26 December great Sumatran-Andaman earthquake in the Indian Ocean caused extensive damage and loss of life from intense shaking and the resulting tsunami. Recent studies of this earthquake have suggested portions of the fault ruptured at variable speeds, with both fast and slow rupture velocities observed along the 1200 km long rupture length [e.g. Ammon et al., 2005]. Variations in rupture velocity along the fault length may indicate along-strike variations in megathrust frictional conditions. Previous work on global subduction zone systems suggests depth dependent frictional conditions arising from heterogeneous conditions along the fault. In many of the circum-Pacific subduction zones, shallow earthquakes along the subduction megathrust have longer scaled source durations than deeper earthquakes, possibly resulting from variations in frictional conditions with depth. A previous analysis of global subduction earthquakes has not shown a clear link between subduction zone features and along-strike variations in earthquake parameters. Here I focus on earthquakes in the Sumatra-Andaman region, examining aftershocks with M greater than 6.0 of the 2004 great earthquake, as well as other earthquakes that occurred in the region between 1992 and 2004. Source duration, depth, and slip distribution are determined for this set of earthquakes to explore the possibility of both along strike and depth dependent variations in source parameters and frictional conditions. Source parameters determined for these earthquakes will be compared with global catalogs of other subduction zone earthquakes. Preliminary results suggest depth dependence of source parameters for these events, with longer scaled durations for the shallower earthquakes, consistent with previous global studies. Along strike patterns are compared with rupture models of the 2004 great earthquake. If slow rupture velocities observed for the 2004 rupture can be linked with variations in megathrust frictional conditions, then along-strike variations in source parameters are likely found in catalogs of smaller magnitude earthquakes.
DE: 7215 Earthquake source observations (1240)
DE: 7240 Subduction zones (1207, 1219, 1240)
SC: Seismology [S]
MN: Fall Meeting 2005