Seismic Activities and Hazards of the Seismic Gaps in the Haiyuan Fault in Northeastern Tibet: Insights From Numerical Modeling Earthquake Interaction

The 2022 Mw 6.6 Menyuan earthquake occurred in the Qilian‐Haiyuan fault system in northeastern Tibet. To investigate the mechanism behind the 2022 Menyuan earthquake and the seismic hazards (SHs) of the Tianzhu seismic gap, the spatiotemporal stress variations on the Qilian‐Haiyuan fault zone were assessed before and after 2022 by modeling the stress changes caused by 12 historical large earthquakes during the last century. The results showed that the 2022 Menyuan earthquake was delayed due to a stress shadow caused by the 1927 Mw 8.3 Gulang earthquake. The stress shadow also covers the middle section of the Tianzhu seismic gap and inhibits its seismic activities to some extent. By preventing the rupture of the Tianzhu seismic gap in a single event, this stress shadow may reduce the risk of a future earthquake with a magnitude of more than Mw 7.7 in the Tianzhu seismic gap (length = approximately 260 km). The western portion of the Tianzhu Seismic Gap (length = approximately 18 km) was stress‐loaded with the peak ΔCFS value of approximately 375.15 kPa due to the 2016 Mw 5.9 and 2022 Mw 6.6 Menyuan earthquakes, indicating its increased SHs. The eastern portion of the Tianzhu seismic gap (length = approximately 149 km) was stress‐loaded with the peak ΔCFS value of approximately 1,035 kPa due to the 1927 Mw 8.3 Gulang and 1920 Mw 8.5 Haiyuan earthquakes, indicating its increased SHs. Therefore, more efforts should be made to prepare for the future hazards prevention in the eastern portion of the Tianzhu seismic gap.