Finite element simulation of stress change for the M_(S)7.4 Madoi earthquake and implications for regional seismic hazards

On May 22,2021,the M_(S)7.4 earthquake occurred in Madoi County,Qinghai Province;it was another strong event that occurred within the Bayan Har block after the Dari M_(S)7.7 earthquake in 1947.An earthquake is bound to cast stress to the surrounding faults,thus affecting the regional seismic hazard.To understand these issues,a three-dimensional viscoelastic finite element model of the eastern Bayan Har block and its adjacent areas was constructed.Based on the co-seismic rupture model of the Madoi earthquake,we analyzed the co-and postseismic Coulomb stress change caused by the Madoi earthquake on the surrounding major faults.The results show that the Madoi earthquake caused significant co-seismic stress increases in the Tuosuo Lake and Maqin-Maqu segments of the East Kunlun fault(>10 kPa),which exceeded the proposed threshold of stress triggering.By integrating the accumulation rate of the inter-seismic tectonic stress,we conclude that the Madoi earthquake caused future strong earthquakes in the Tuosuo Lake and Maqin-Maqu segments of the East Kunlun fault to advance by 55.6-623 and 24.7-123 a,respectively.Combined with the influence of the Madoi earthquake and the elapsed time of the last strong earthquake,these two segments have approached or even exceeded the recurrence interval of the fault prescribed by previous research.In the future,it is necessary to focus greater attention on the seismic hazard of the Maqin-Maqu and Tuosuo Lake segments.This study provides a mechanical reference to understand the seismic hazard of the East Kunlun fault in the future,particularly to determine the seismic potential region.