A Future Scenario Earthquake: Dynamic Rupture simulation on Wenchuan-Maoxian Fault

The 2008 Wenchuan Mw 7.9 mainshock and aftershocks rupture the Beichuan Fault (BCF) and Pengguan fault (PGF), having caused catastrophic destruction to cities and counties along the northwestern margin of the Sichuan basin. The Wenchuan-Maoxian Fault (WMF) on the hinterland side along with a conjugate buried Lixian fault (LXF) were not activated by this earthquake, but is likely to experience large earthquakes in the future due to similar seismicity with regard to other two ruptured faults. We perform 3D dynamic earthquake rupture simulations on the WMF and LXF, to explore possible size of earthquakes and distribution of high seismic risk in the future. We firstly invert 391 focal mechanism solutions (FMS) of earthquakes (M 3.5) that occurred between 2009 and 2016 in the Longmen Shan, to get heterogeneous tectonic stress field as initial stress of simulation. Then we develop a new method to set up fault geometry through inverting long-term slip rates, which is based on the WallaceBott hypothesis. Our simulation results show that the dynamic rupture may start in the LXF, leading to magnitude-6.9 earthquakes; or, start in the WMF, then cascades through the LXF, leading to magnitude-7.4 earthquakes. We also find that the cascade rupture tends to jump from oblique fault to strike-slip fault, but reverse is more difficult. In addition, the surface displacements derived from simulations show that maximum coseismic slips are distributed in the areas near fault intersection and Maoxian County, which suggest higher seismic risk in the future.