Crustal model of Lake Van Basin and Accurate Hypocentre Determination of 23 October Lake Van Earthquake (Mw:7.1) and Its Aftershocks

Abstract We present a one-dimensional (1-D) velocity model of Lake Van basin and its surrounding and precise hypocenter locations by using 23 October 2011 (Mw = 7.1) Lake Van earthquake aftershock data, and the VELEST program which calculates 1-D minimum velocity model from body wave travel times together with station corrections. The study area covers a 180x90 km2 area centered at Lake Van. Ten new seismic stations were deployed after the 23 October 2011 Lake Van earthquake covering Lake Van region by Kandilli Earthquake Research Institute. After merging all available seismic station data in the region, we manually analyzed 7643 events that occurred from 23 October 2011 to 21 January 2015. We selected 1193 well-located events recorded by 16 stations with 48387 P- and 26913 S- arrival times for iterative simultaneous inversion of velocity and hypocenter parameters. During the inversion, near-surface velocity heterogeneity and station elevation influence were eliminated by station corrections. We computed Vp and Vp/Vs ratio of eight layers within 39 km depth with a 3 km thick sedimentary layer. Several tests were applied to ensure the stability of the velocity structure and accuracy of the aftershock locations. The aftershock sequence with the new 1-D velocity model was relocated and a drastic change was observed in the distribution whereas the new locations moved to the main shock area.