HR: 0800h
AN: G51C-0846    [Abstracts]
TI: InSAR constraints on the kinematics and magnitude of the 2001 Bhuj earthquake
AU: * Schmidt, D
EM: das@uoregon.edu
AF: Univeristy of Oregon, Geological Sciences 1272 University of Oregon, Eugene, OR 97403-1272 United States
AU: Bürgmann, R
EM: burgmann@seismo.berkeley.edu
AF: University of California, Berkeley, Earth and Planetary Sciences 307 McCone Hall, Berkeley, CA 94720-4767 United States
AB: The Mw 7.6 Bhuj intraplate event occurred along a blind thrust within the Kutch Rift basin of western India in January of 2001. The lack of any surface rupture and limited geodetic data have made it difficult to place the event on a known fault and constrain its source parameters. Moment tensor solutions and aftershock relocations indicate that the earthquake was a reverse event along an east-west striking, south dipping fault. In an effort to image the surface deformation, we have processed a total of 9 interferograms that span the coseismic event. Interferometry has proven difficult for the region because of technical difficulties experienced by the ERS Satellite around the time of the earthquake and because of low coherence. The stabilization of the orbital control by the European Space Agency beginning in 2002 has allowed us to interfere more recent SAR data with pre-earthquake data. Therefore, all available interferograms of the event include the first year of any postseismic deformation. The source region is characterized by broad floodplains interrupted by isolated highlands. Coherence is limited to the surrounding highlands and no data is available directly over the epicenter. Using the InSAR data along two descending and one ascending tracks, we perform a gridded search for the optimal source parameters of the earthquake. The deformation pattern is modeled assuming uniform slip on an elastic dislocation. Since the highland regions are discontinuous, the coherent InSAR phase is isolated to several individual patches. For each iteration of the gridded search algorithm, we optimize the fit to the data by solving for number of 2π phase cycles between coherent patches and the orbital gradient across each interferogram. Since the look angle varies across a SAR scene, a variable unit vector is calculated for each track. Inversion results place the center of the fault plane at 70.33° E/23.42° N at a depth of 21 km, and are consistent with the strike and dip suggested by the relocated aftershocks. The data also constrain the magnitude, rake, and finiteness of the event.
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 7215 Earthquake source observations (1240)
DE: 8108 Continental tectonics: compressional
DE: 9320 Asia
SC: Geodesy [G]
MN: Fall Meeting 2005