Numerical simulation of seismic stress evolution in the Lajishan Fault zone on the northeastern margin of the Qinghai-Xizang Plateau

To analyze the triggering relationship of historical earthquakes to the 2023 Jishishan earthquake and estimate the seismic risk in the adjacent region after the earthquake, we calculate the evolution process of seismic stress generated by 11 earthquakes with M S ≥ 6.0 and 1 earthquake with M S 5.7 near the source in the past 100 years. The results show that before the 2023 Jishishan earthquake, the entire Lajishan Northern Edge Fault zone was under the stress shadow generated by the 12 earthquakes. The stress reduction at the 2023 Jishishan earthquake epicenter was approximately 15.1 kPa, and the contribution of this stress shadow mainly comes from the 1920 M S 8.5 Haiyuan earthquake. The coseismic stress drop at the epicenter was around −292.1 kPa, and the maximum stress drop for the 2023 Jishishan earthquake was around −346.2 kPa. The Jishishan earthquake increased the stress of the two seismic gaps in the Lajishan Northern Edge Fault by 14.7 kPa and 59.7 kPa respectively, the stress on the Lajishan Southern Edge Fault zone increased by 10.9 kPa, and the stress on the east section of Xunhua Nanshan Fault increased by 11.1 kPa. These stress increments potentially elevate the seismic hazard along these fault zones. In the future earthquake prevention and disaster reduction, attention should be paid to the seismic risk of these fault zones.