Future Scenario Earthquakes Dynamic Rupture simulation on the Wenchuan-Maoxian Fault in the Longmen Shan, China, thrust belt

The 2008 Wenchuan Mw 7.9 mainshock has caused catastrophic destruction to cities 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) was not activated by this earthquake but is likely to experience large earthquakes in the future. We perform 3D dynamic earthquake rupture simulations on the WMF and LXF to access the possibility of the earthquake occurrence and further explore the possible size of earthquakes and the distribution of high seismic risk in the future. We firstly invert focal mechanism solutions to get a heterogeneous tectonic stress field as the initial stress of simulation. Then we develop a new method to refine fault geometry through inverting long-term slip rates. Several fault nucleation points, friction coefficients, and initial stress states are tested, and the general rupture patterns for these earthquake scenarios are evaluated and could fall into three groups. Depending on initial conditions, the dynamic rupture may start in the LXF, leading to magnitude-7.0 earthquakes, or start in the WMF, then cascades through the LXF, leading to magnitude-7.5 earthquakes, or both start and arrest in the WMF, leading to around magnitude-6.5 or 7.0 earthquakes. We find that the rupture starting on the reverse oblique-slip tends to jump to the strike-slip fault, but the reverse process is suppressed. The rupture propagating eastward causes larger coseismic displacements than the westward propagation, and relatively high peak ground velocities are distributed near the northeastern end of WMF.