Rupture Process of the 23 October 2011 Mw7.1 Van Earthquake in Eastern Turkey by Joint Inversion of Teleseismic, GPS and Strong-Motion Data

Abstract

On 23 October 2011, a strong earthquake (Mw = 7.1) struck the Van (Eastern Turkey) region and its surrounding areas at 10:41:22 UTC (hereafter referred to as the Van earthquake), causing severe damage to the source region. Several studies have been carried out on the focal mechanism, seismic moment, focal depth and rupture model of this earthquake. However, there are still significant differences in the moment release, focal depth and slip asperities among these models. Since most of these models only used a single data set to investigate the source parameters, the reliability of these results is still a concern. In order to make clear the uncertainties and provide a reliable detailed rupture model for the mainshock, we investigated the rupture process of the Van earthquake by a joint inversion of teleseismic broadband seismograms, near-field static GPS displacement records and strong-motion data. The inversion results indicate that the mainshock was dominated by a thrust slip with a small part of a left-lateral strike-slip component below the hypocenter. The rupture initiated at a focal depth of 16 km and propagated to the surface with a relatively low average rupture velocity of ~1.8 km/s, suggesting that the major energy of the earthquake was released in a long-period band, which is the main reason why the seismic moments inverted by a long period or static signals are higher than those obtained by short-period data. Most of the slip occurred around the hypocenter with a maximum slip of more than 3.3 m, and the associated static stress drop was ~3 MPa. The total seismic moment of the whole fault was 5.76 × 1019 N·m, and most energy was released in the first 20 s, which is in the variation range of the released rupture models. The major slip was concentrated at deeper depth and extended to a depth of around 25 km. Meanwhile, the surface rupture was quite small, which explains why only weak ruptures were observed at the surface although caused by such a strong earthquake.