Crustal Flow-Induced Earthquake Revealed by Full-Waveform Tomography and Implications for Prehistoric Civilization Destruction

Abstract

The 2023 Jishishan earthquake resulted in significant casualties and extensive damage to community infrastructure. To understand its seismogenesis, we employed state-of-the-art full-waveform tomography to obtain high-resolution, multiparameter seismic models of the crust surrounding the epicenter. The earthquake's hypocenter was situated in a transition zone with substantial variations in seismic structure. Notably, the mid-lower crust of the plateau's interior exhibited pronounced low-velocity zones, positive radial anisotropy (V_SH > V_SV), and high Vp/Vs ratio. Conversely, the plateau's margin showed relatively high velocities and low Vp/Vs ratio anomalies. Radial anisotropy in the hypocenter region, characterized by negative values (V_SH < V_SV), indicates a predominantly vertical deformation regime. We suggest that the outward flow of mid-lower crustal material, resisted by more stable marginal regions, leads to stress accumulation in the overlying crust, resulting in earthquakes. Furthermore, the destruction of the nearby prehistoric Lajia Ruins, partly attributed to ancient earthquakes, highlights the significant impact of the Tibetan Plateau's lateral expansion on the evolution of surrounding civilizations.