The seismic mechanisms and seismogenic environment of the Ms 6.2 earthquake in Jishishan, Gansu, China: Evidence from relocation, focal mechanisms, and rupture processes

Recently, the research achievements of Xu Tairan, an engineer from the China Earthquake Networks Center, and his team were published online in the journal Earth and Planetary Physics. Following the Ms 6.2 earthquake in Jishishan County, Gansu Province, China, in 2023, the research team utilized methods such as relocation, focal mechanism solutions, and rupture process inversion to reveal the seismogenic structural characteristics of this earthquake. The results indicated that the main shock and aftershocks were concentrated at a depth of 12 km, with high consistency in depth exploration across multiple methods. The aftershocks extended unilaterally in the NNW direction, and the main shock was a reverse thrust event with a small dextral strike-slip component. The study also incorporated historical GPS observations, geological surveys, and regional principal stress field data, inferring that the earthquake was triggered by the activity of the main fault at the northern margin of the Lajishan Fault, which activated some secondary faults. The compressive forces on both sides of the Lajishan Fault Zone led to mountain uplift and landslides, ultimately causing the disaster. The research further discussed the activity relationships between the 2022 Ms 6.9 Menyuan earthquake, the 2019 Ms 5.7 Xiahe earthquake, and the Jishishan earthquake under regional stress, providing new evidence and cross-scale analytical insights for studying the seismogenic mechanisms of the Lajishan Fault Zone. For details, refer to the original article.