Zhao Bin, Bürgmann Roland, Wang Dongzhen, Zhang Jian, Yu Jiansheng, Li Qi
Key Laboratory of Earthquake Geodesy, Institute of Seismology, China Earthquake Administration, Wuhan, 430071, China.
Institute of Disaster Prevention, Yanjiao, Sanhe City, Hebei Province, 065201, China.
Nat Commun. 2022 Jun 2;13(1):3098. doi: 10.1038/s41467-022-30883-7.
The frictional properties and slip behaviors of subduction thrusts play a key role in seismic and tsunami hazard assessment, especially in weakly coupled "seismic gaps". Here, we rely on GPS observations in the Shumagin Gap of the Aleutian subduction zone to derive the slip distribution of the 2020 Mw 7.8 Simeonof Island, Alaska earthquake and of the subsequent afterslip during the first 87-day period. Our modeling results show that the mainshock ruptured at depths of ∼30-40 km beneath Simeonof Island. Kinematic and stress-driven models indicate that the afterslip occurred both updip and downdip of the mainshock rupture. Physically plausible locking models derived from interseismic GPS velocities suggest that the 2020 Simeonof and 2021 Mw 8.2 Chignik earthquakes ruptured persistent asperities on the subduction thrust. We infer that there are several additional persistent asperities at depths of 20-50 km west ∼157°W. However, it is still uncertain whether there are additional locked asperities at shallow depths because of the current lack of geodetic observations close to the trench.
俯冲逆冲断层的摩擦特性和滑动行为在地震和海啸灾害评估中起着关键作用，特别是在弱耦合的“地震空区”。在此，我们依靠阿留申俯冲带舒马金空区的GPS观测数据，来推导2020年阿拉斯加锡莫诺夫岛Mw 7.8级地震以及随后87天内余滑的滑动分布。我们的模拟结果表明，主震在锡莫诺夫岛下方约30 - 40千米深处破裂。运动学和应力驱动模型表明，余滑发生在主震破裂的上倾和下倾方向。根据震间GPS速度推导的物理上合理的锁定模型表明，2020年锡莫诺夫地震和2021年Mw 8.2级奇尼克地震破裂了俯冲逆冲断层上的持续凹凸体。我们推断，在西经约157°以西20 - 50千米深处还有几个额外的持续凹凸体。然而，由于目前在靠近海沟处缺乏大地测量观测数据，浅部是否存在额外的锁定凹凸体仍不确定。
