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 field investigations and 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 offsets are up to (3.9, 3.6, 4.1) m in the east, north, and up directions respectively, i.e., 2.9 and 4.1 m 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 m at depth of 4–8 km beneath Muzaffarabad. We find a scalar moment of 2.34 × 1020 N m (Mw7.55), of which almost 82% is released in the uppermost 10 km.