Fault Process and Broadband Ground-Motion Simulations of the 23 October 2011 Van (Eastern Turkey) Earthquake
Abstrakt
On 23 October 2011 an M-w 7.1 earthquake occurred in eastern Turkey, close to the towns of Van and Ercis, causing more than 600 casualties and widespread structural damage. The earthquake ruptured a 60-70 km long northeast-southwest fault with a thrust mechanism, in agreement with regional tectonic stress regime.
We studied the fault process of the event and the recorded ground motions using different sets of data. Regional records (0.005-0.010 Hz) are used to constrain the centroid moment tensor solution.
Near-regional data, 100-200 km from the fault, are used for relocation of the hypocenter and, in the frequency range 0.05-0.15 Hz, for inversion of the rupture propagation by two methods: multiple point-source model (ISOLA) and multiple finite-extent (MuFEx) source model. MuFEx also provides an estimate of the model uncertainty, which is quite large due to unfavorable station distribution.
We arrive at several plausible scenarios (equally well fitting the observed data including Global Positioning System coseismic displacements) with different styles of the rupture propagation. A few alternative source models are used for broadband (0.1-10 Hz) ground-motion simulations by means of the hybrid integral-composite source model.
Only models comprising source complexities, such as a delayed rupture of shallow asperities, enable explanation of the acceleration record at the only available near-fault station, which exhibits a long duration and two prominent wave groups. These complex rupture models are used to simulate the ground motion in the near-fault area, specifically, at Van and Ercis, where records of the mainshock were missing, providing reasonable agreement with the observed spatial distribution of damage.