Revealing the slip distribution and seismogenic structure of the magnitude 6.2 Jishishan (Gansu) earthquake in 2023 through multi-source InSAR observations

On 18 December 2023, Jishishan County in Gansu Province, China, was struck by an earthquake with magnitude 6.2, resulting in considerable loss of life and property. The seismogenic fault and rupture model of the event has sparked significant controversy, leading to diverse opinions among researchers. Some attribute the earthquake to the northern segment of the west-dipping Lajishan fault, whereas others consider an east-dipping blind fault on the Jishishan fault to be the seismogenic fault. This study integrates InSAR observations, aftershock relocation, and active tectonic analysis to determine the structure and rupture characteristics of seismogenic faults. Considering the active fault distribution, a listric fault model has emerged as the most plausible source of this earthquake event. The model of this study suggests a hidden branch of the southern segment of the Lajishan fault, whose reverse movement caused an uplift in the shallow crust. Supported by InSAR-derived coseismic deformation data and relocated aftershocks, this seismogenic model provides valuable insights into the regional tectonic framework. This study emphasizes the complexity of fault systems involved in earthquake genesis and contributes to a deeper understanding of seismic risk in the area.