Causative fault and seismogenic mechanism of the 2010 Suining M5.0 earthquake from joint modeling of seismic and InSAR data

Although the Sichuan basin is a stable block with low historical seismicity, the Suining M5.0 earthquake on January 31, 2010 occurred near the center of the basin, causing casualty and substantial damage. Previous studies have shown that the earthquake is very shallow and may occur in the sedimentary cover rocks, but its causative fault has not been identified. Based on local broadband seismic waveform data as well as a pair of ALOS PALSAR ascending orbit data, we explore the seismogenic mechanism via further constraining the source depth and the ruptured fault. The earthquake caused ground uplift in the southeast of the epicenter area, with a maximum line of sight displacement of about 13.6 cm, much larger than the displacement caused by a M5 earthquake at a typical depth of 10 km, which indicates that the earthquake is very shallow. Through joint inversion of seismic waveform and InSAR data, we obtain the moment magnitude of Suining earthquake as M(W)4.5, with the strike, dip, and rake of its fault plane as 17 & DEG;, 66 & DEG; and 90 & DEG;, respectively, and the centroid depth less than 1 km, supporting that the earthquake occurred at the shallow part of a high angle thrust fault dipping to the southeast. It is further confirmed that the earthquake may be triggered by the diffusion of high-pressure fluid migrating from the underside gas reservoir.