Abstract: The Yutian region is located at the intersection region of borderland of the Tibet Plateau and Tarim craton. Four major earthquakes all occurred around the southwestern end of the Altyn Tagh Fault zone since 2008. The earthquake sequence provides a great opportunity to study the spatial distribution of regional moderate strong earthquakes and their interaction. Firstly, we analyze the seismicity in the Yutian region using small earthquake catalogue since 1970, and present a spatial pattern of b-value. Then, we calculate stress migration between 4 major earthquakes since 2008 using a layered viscoelastic dislocation model. We found that the migration of major earthquakes in Yutian region may be controlled by crustal stress level. More historical earthquakes were recorded along the Kangxiwar fault, and b-value derived from background seismicity is relative higher. In contrast, b-value along the Longmu Co-Guozha Co fault zone, the southern branch of the Altyn Tagh fault, is relative lower, while strong earthquake occurred frequently in recent years. In addition, the stress transfer caused by the 4 strong earthquakes in Yutian area is complicated. The ΔCFS that produced by the 2008 earthquake have negative effects on the occurrence of the 2012 event. While occurrence of the 2014 and 2020 events are both promoted by previous major earthquakes. Based on the results of seismic activity and stress transfer, it can be concluded that the crustal stress near the Longmu Co-Guozha Co fault zone is still relatively high, hence still with relative higher potential seismic risk in future.

Key words: Yutian earthquake sequence, Altgn Tagh fault, seismicity, ΔCFS