3-D Coseismic Displacement Field of the 2005 Kashmir Earthquake Inferred from Satellite Radar Imagery

We use radar amplitude images acquired by the ENVISAT/ASAR sensor to measure the coseismic deformation of the 8 October 2005 Kashmir earthquake. We use the offset images to constrain the fault trace, which is in good agreement with the field investigations and the aftershock distribution. We infer a complete 3-D surface displacement field of the Kashmir earthquake using the offset measurements derived from both descending and ascending pairs of SAR images. The peak-to-peak offset is up to (3.9, 3.6, 4.1) meters in the east, north, and up directions respectively, i.e., 2.9 and 4.1 meters along and across the fault assuming striking 325. We model the coseismic displacements using a four-segment dislocation model in a homogeneous elastic half-space. We first estimate the source parameters using a uniform slip model. Then we fix the optimal geometric parameters and solve for the slip distribution using a bounded variable least-squares (BVLS) method. The resultant maximum slip is about 9.0 meters at depth of 4-8 km beneath Muzaffarabad. We find a scalar moment of 2.34 × 10 Nm (Mw7.55), of which almost 82% is released in the uppermost 10 km.