A systematic method to develop dynamic earthquake rupture scenarios: A case study on the Wenchuan–Maoxian Fault in the Longmen Shan, China, thrust belt

Ryosuke Ando, & Rongjiang Tang

Submitted September 10, 2023, SCEC Contribution #12833, 2023 SCEC Annual Meeting Poster #107

The 2008 Wenchuan Mw 7.9 mainshock caused catastrophic destruction to cities along the northwestern margin of the Sichuan Basin. This earthquake did not activate the Wenchuan–Maoxian Fault (WMF) on the hinterland side and the conjugate buried Lixian Fault (LXF), but they could experience large earthquakes in the future. We propose a systematic method to develop scenario earthquakes for active fault systems with insufficient structural data to constrain the 3D fault geometries. We first performed stress tensor inversion to constrain the regional stress field. Then, we developed a new method to constrain fault geometries by inverting long-term slip rates under the given regional stress and applied it to the WMF . We conducted a set of 3D dynamic earthquake rupture simulations on the WMF and LXF to assess the scenarios of earthquake rupture processes. Several fault nucleation points, friction coefficients, and initial stress states are assessed, the general rupture patterns for these earthquake scenarios are evaluated, and finally, we find the scenario that 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 jumps to the strike-slip fault, but the reverse process is suppressed.

Key Words
Fault geometry inversion, Longterm slip rate, Regional stress, Dynamic rupture simulations

Citation
Ando, R., & Tang, R. (2023, 09). A systematic method to develop dynamic earthquake rupture scenarios: A case study on the Wenchuan–Maoxian Fault in the Longmen Shan, China, thrust belt. Poster Presentation at 2023 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)