东昆仑断裂带玛沁—玛曲段三维形变研究

doi:10.12196/j.issn.1000-3274.2023.04.011

摘要/Abstract

摘要： 东昆仑断裂带是青藏高原内部最活跃的左旋走滑断裂之一, 是巴颜喀拉地块的北部边界。东昆仑断裂东段的玛沁—玛曲段是近400年来5级以上地震空区。本文基于PS-InSAR技术, 利用欧空局Sentinel-1A/B卫星升降轨SAR数据获取玛沁—玛曲段的震间LOS向形变速率场, 结合GNSS数据插值解算欧亚参考框架下的三维速率场, 合成平行于断层走向的速度场; 然后利用马尔可夫链蒙特卡罗方法反演玛沁—玛曲段及周围断层的滑动速率和闭锁状态。研究结果表明, 玛沁—玛曲段未发现明显的蠕滑现象, 其滑动速率从距离东昆仑末端300 km左右的阿尼玛卿山开始由西向东逐渐减小, 由4.7 mm/a逐渐减小到2.3 mm/a; 玛沁—玛曲段大部分存在10 km以上的闭锁深度, 并且在不断积累应变, 已接近古地震的复发周期。玛沁段与玛曲段的地震矩积累均可达到1.00×10²⁰ N·m, 均相当于一次M_W7.3地震的能量; 若两段同时破裂, 释放的地震矩能量相当于一次M_W7.5地震, 因此玛沁—玛曲段的地震危险性值得关注。

关键词: 玛沁—玛曲段, InSAR, 三维形变, 断层闭锁, 滑动速率

Abstract: The East Kunlun Fault (EKF) is one of the most active left-lateral strike-slip faults located in the Qinghai-Tibet Plateau, and it is the northern boundary of the Bayan Har Block. The Maqin-Maqu segment of the East Kunlun Fault is a M_W5.0 earthquake gap in the past 400 years. Based on PS-InSAR technology, we use Sentinel-1A/B Ascending and Descending SAR data from European Space Agency to obtain the LOS deformation velocity of the Maqin-Maqu segment. Combined with GNSS data, the three-dimensional velocity and fault-parallel velocity under the Eurasian reference frame are derived. Then, the Markov chain Monte Carlo method is used to invert the slipping rate and locking depth of the Maqin-Maqu segment and its surrounding faults. The results indicate that no obvious creep has been observed in the Maqin Maqu section. From west (Animaqing Mountain, 300 km away from the end of the East Kunlun fault) to east, the slipping rate gradually decreases from 4.7 mm/a to 2.3 mm/a. The Maqin-Maqu segment has a locking depth more than 10 km, resulting in sustained strain accumulation and closing to the recurrence. The cumulative seismic moments of both Maqin and Maqu segments reach ~1.00×10²⁰ N·m, equalling to an M_W7.3 earthquake. If the two segments rupture simultaneously, the released seismic moment energy is equivalent to an M_W7.5 earthquake. The seismic risk of the Maqin-Maqu segment is worth poajing attention to.

Key words: Maqin-Maqu section, InSAR, Three-dimensional deformation, Fault coupling, Slip rate

中图分类号:

P315.7

张夏, 董彦芳, 洪顺英. 东昆仑断裂带玛沁—玛曲段三维形变研究[J]. 地震, 2023, 43(4): 169-184.

ZHANG Xia, DONG Yan-fang, HONG Shun-ying. Research on the Three-Dimensional Deformation along the Maqin-Maqu Section of the East Kunlun Fault zone from InSAR[J]. EARTHQUAKE, 2023, 43(4): 169-184.

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