[S-SS07] Seismic wave propagation: Theory and Application

[SSS07-P21] Asymmetric bi-lateral rupture of the 2022 Ms 6.8 Luding earthquake on a continental transform fault, Tibetan border, China

*Yijun Zhang¹ (1.Chinese Acedemy of Sciences, China)

Keywords:asymmetric bilateral evolution, the seismic potential

The Xianshuihe (XSH) fault on the eastern boundary of the Tibetan plateau is one of the most active faults in the world. However, the Moxi fault, the southernmost segment of the XSH fault, remained seismically quiescent for over 230 years, along a fault with large historic slip rate and recently measured geodetic locking. This region was thus considered to be a seismic gap capable of hosting earthquakes of Mw 7.0 or greater. In September 2022, the Ms 6.8 Luding earthquake occurred on the Moxi fault, resulting in destructive landslide damage, with 93 people dead and 25 missing. Using regional and global seismic recordings, we performed a multiple-point source analysis, finite fault inversions, and backprojection imaging to investigate in detail the rupture process associated with the 2022 Luding, China, earthquake. Our model results show that this event is characterized by asymmetric bilateral evolution with three episodes: (1) an initial bilateral rupture propagation mainly toward NNW; (2) major rupture propagating toward SSE and up-dip direction; (3) SSE-rupture propagation speed accelerates to ~2 km/s. The rupture toward NNW is dominated by high-frequency (1-2 Hz) seismic radiation. Over 70% of the seismic moment is released at shallow depths <12 km thus explaining significant damaging effects. Furthermore, based on the analysis of Coulomb stress changes, the seismic potential of the remaining locked portions of the XSH and Anninghe faults is still high due to the stress loading imposed by the Luding earthquake.