Geodetic constraints on postseismic deformation following the Mw 7.2 October 23, 2011 Van earthquake (E.Turkey)

Abstract:

We have studied postseismic deformation of the 23 October 2011, Mw=7.2 Van (E. Turkey) Earthquake associated with reverse faulting on a NE-SW trending and northward dipping fault. Postseismic surface displacements between November 2011 and May 2014 are derived from continuous GPS stations in the far field and survey-type GPS measurements carried out in a geodetic network we established after the earthquake in the near field. Total horizontal displacements 2.5 years after the earthquake reach 30 cm at some sites near the fault. The pattern of GPS displacements suggests that the early postseismic deformation is most probably due to shallow after slip that appears to decrease exponentially with time.

We model the GPS measurements using dislocations on triangular planes in a homogenous and elastic half space and Coulomb stress. Elastic dislocation and Coulomb stress modeling indicate that the postseismic deformation can be adequately explained by shallow slip on the coseismic fault and a fault splay on the footwall block, and is likely driven by coseismic stress changes.

Keywords: 2011 Van earthquake, GPS, postseismic deformation, afterslip, elastic dislocation