Source Parameters of the 1 May 2013 mb 5.7 Kishtwar Earthquake: Implications for Seismic Hazards

Abstract

Abstract We study the source mechanism and depth of the recent moderate earthquake, which occurred on 1 May 2013 in the Kashmir seismic gap. The epicenter of the earthquake lies southeast of the Kashmir valley and close to the meisoseismal zone of the 1555 Kashmir earthquake (magnitude ∼7.6). This event provides an excellent opportunity in which to study the seismotectonics of the Kashmir Himalaya using global digital seismic data. We modeled the source parameters of the earthquake by least‐squares fitting of the teleseismic P ‐ and SH ‐waveform data. The minimum‐misfit solution reveals that the earthquake occurred on an oblique thrust fault with strike, dip, and rake of 346°, 26°, and 121°, respectively, and originated at a depth of 16±3 km. The strike of the fault plane matches that of the mapped Himalayan thrust faults in the region, and its depth puts it within the Himalayan wedge, close to the basal decollement (main Himalayan thrust [MHT]). However, the dip of the causal fault plane is larger than the inferred dip of the MHT and therefore requires the earthquake to have occurred on a ramp or a splay thrust. The most likely candidate is the main boundary thrust the downdip end of which matches with the geometry of the fault plane and coincides with the observed hypocentral distribution of small‐to‐moderate earthquakes in the region. We synthesize our findings with geodetic measurements from the Kashmir Himalaya to show that the hypocentral zone of this event marks a region of strain accumulation beneath the Kashmir seismic gap. This region could possibly be the point of initiation of a future great earthquake. We conclude by highlighting the outstanding questions in assessing seismic hazards in this region and designing a broadband seismological field experiment that is currently being undertaken to address these important issues.