Triggering effect of historical earthquakes in the northern Tibetan Plateau on the Coulomb stress of the 2022 Menyuan MS6.9 earthquake and subsequent earthquakes

We employ the Burgers viscoelastic model to investigate the Coulomb stress change on the Menyuan M(S)6.9 earthquake that occurred on January 8, 2022. We aim to explore the viscoelastic triggering effect of strong historical earthquakes in the northern Tibetan Plateau since 1125 AD on the Menyuan earthquake and its impact on subsequent earthquakes. The results reveal that the Haiyuan M81/2 earthquake in 1920, the Gulang M8.0 earthquake in 1927, and the Shandan M71/4 earthquake in 1954 have the most significant loading effect on the Menyuan earthquake in 2022. These historical earthquakes advance the occurrence of the Menyuan earthquake by 7.6 years, 5.3 years, and 5.22 years, respectively. Additionally, the 1986 Menyuan M(S)6.4 earthquake has the most prominent unloading effect on the 2022 Menyuan earthquake, delaying its occurrence by approximately 14.4 years. Furthermore, the 2021 Madoi M(W)7.3 earthquake has a significant triggering effect on the Menyuan earthquake in 2022, while the Menyuan M(S)6.9 earthquake triggers the Hala Lake M5.8 earthquake on January 23, 2022. The Hala Lake M5.8 earthquake has a strong triggering effect on the Sunan M5.1 earthquake on March 17, 2022, as well as the Hala Lake M6.0 earthquake on March 26, 2022. Finally, the Hala Lake M6.0 earthquake triggers the Hala Lake M5.4 earthquake on April 15, 2022. Based on the comprehensive analysis of the Coulomb stress evolution results of strong historical earthquakes and the influence of faults by viscoelastic Coulomb stress of historical earthquakes, we conclude that the stress accumulation in this area is high. The internal faults of Qilian Mountain are prone to instability and sliding when disturbed by stress, including the vicinity of the Menyuan earthquake area, the northern part of Halahu Lake in the western part of Qilian Mountain, the western part of Laohushan fault, the middle part of the northern margin of Qilian Mountain, the middle part of Changma-Ebo fault, the Altyn Tagh Fault (Aksai segment), the western part of Tolaishan fault, Elashan fault, and DachaidanZongwulongshan fault, and should be fully considered in the future.