Highlights:
The 2022 Mw 6.6 Menyuan earthquake was delayed due to the stress shadow caused by historical earthquakes in northeastern Tibet.
The stress shadow covers the middle section of the Tianzhu Seismic Gap and prohibits its seismic activity.
The eastern portion of the Tianzhu Seismic Gap was stress loaded by historical earthquakes, indicating its increased seismic hazards.
Abstract: The 2022 Menyuan earthquake occurred in the Qilian-Haiyuan fault system in northeastern Tibet. To investigate the reason behind this earthquake and the seismic hazards of the Tianzhu Seismic Gap, we demonstrated the spatiotemporal stress variation on the fault system before and after 2022 through numerical modelling. We found that the 2022 earthquake was delayed due to a stress shadow caused by historical earthquakes. This stress shadow also covers the middle of the Tianzhu Seismic Gap and prohibits its seismic activities to some extent. Acting as a stress barrier to prevent the Tianzhu Seismic Gap rupturing in one event, this stress shadow may decrease the possibility of generating a future earthquake of magnitude more than Mw7.7 in this gap. The east portion of the Tianzhu Seismic Gap was stress loaded, indicating its increased seismic hazards. Attention should be paid to the hazards prevention in the eastern portion of the gap.
Plain Language Summary: The 2022 Mw 6.9 Menyuan earthquake occurred in the Qilian-Haiyuan fault system in northeastern Tibet. In this study, we demonstrated the space-time stress variation along the Qilian-Haiyuan fault system by calculating the stress change by several large earthquakes in the target region in the past century. We found a earthquake-induced stress shadow delayed the 2022 Menyuan earthquake. The seismic activities in the middle section of the Tianzhu Seismic Gap (to the east of the Qilian-Haiyuan fault system) are also prohibited by the this stress shadow. However, the east portion of the Tianzhu Seismic Gap was stress loaded by historical earthquake, indicating its increased seismic hazards. More attention should be paid to the future seismic hazards in the eastern portion of the Tianzhu Seismic Gap. It is helpful for hazards prevention and disaster relief for the government of Gansu province, China.
Keywords: The 2022 Menyuan earthquake, Tianzhu Seismic Gap, Haiyuan fault, Stress shadow, Stress trigger