Evidence for Tear Faulting from New Constraints of the 23 October 2011 Mw 7.1 Van, Turkey, Earthquake Based on InSAR, GPS, Coastal Uplift, and Field Observations

The 23 October 2011 M 7.1 Van earthquake in eastern Turkey took place on a previously unknown thrust fault, causing over 600 fatalities and extensive damage mainly in Van city and the northern town of Erciş. Several coseismic models have already been published after the earthquake using the available seismological and geodetic data. These studies generally agree on a coseismic rupture on a north-dipping east–west-trending blind-thrust fault comprising one or two subparallel segments and the existence of a shallow slip deficit. Here, by introducing an additional coseismic pixel-offset dataset from the TerraSAR-X satellite, we conclude that a NNE–SSW-trending left-lateral tear fault that bounds the rupture to the east also slipped both during and after the mainshock, which is in agreement with both field observations and postseismic Global Positioning System (GPS) measurements. This has important implications for the seismic hazard analysis of the region as the extent and geometry of the rupture that we infer differ significantly from those previously proposed.