1997年以来巴颜喀拉块体周缘强震之间的黏弹性触发研究

2021年5月22日在青海玛多发生M_W7.4地震，为了探究玛多地震的不同滑动模型对周围地区及断层应力的加卸载作用，本文首先以GNSS数据为约束，结合中国地震局地质研究所公布的玛多地震同震滑动模型（模型A）断层面几何结构反演获得同震滑动模型（模型C），再分别利用模型A、模型B（USGS）、模型C计算玛多地震对周围地区及断层的应力加卸载作用。结果显示：① 模型C矩震级为M_W7.46，最大滑动量为3.39 m，主体破裂位于0—10 km深度范围，整体破裂东侧大于西侧，滑动分布相对于模型A也更加均匀平滑，反演效果较好；② 不同模型计算的应力分布基本相同，沿破裂段同震库仑应力加载区域面积随着深度的增加而增加，且在发震断裂带西端、东端分别各有两处明显的库仑应力加载区域，在昆仑山口—江错断裂东、西段、甘孜—玉树断裂、东昆仑断裂东段、玛多—甘德断裂、清水河断裂中、西段、达日断裂西段均产生了明显的应力加载，但模型B计算结果有所差异，昆仑山口—江错断裂中段处于应力卸载状态，震后10年断层应力状态变化不大，但清水河断裂东段在震后应力调整中卸载作用较为明显，地震危险性降低；③ 为了探究强震对玛多地震的影响，本文分别计算了2008年汶川地震以后巴颜喀拉地块M≥7.0强震同震及震后效应对玛多地震的应力加卸载，结果表明所有强震均对玛多地震有应力加载作用，但累积库仑应力并未超过触发阈值。

Coulomb stress interaction among strong earthquakes around the Bayan Har block since the Manyi earthquake in 1997

On May 22, 2021, the M_W7.4 earthquake occurred in Madoi, Qinghai. In order to explore the loading and unloading effects of different sliding models of Madoi earthquake on the surrounding areas and fault stresses, in this paper, the co-seismic sliding model （Model C） is obtained by taking GNSS data as a constraint combining the inversion of the geometric structure of the fault plane of Model A （Institute of Geology, China Earthquake Administration）, and then the loading and unloading effects of Madoi earthquake on the surrounding areas and fault stresses are calculated by using Model A, Model B （USGS）, and Model C respectively. The results show that: ① The moment magnitude of Model C is M_W7.46, the maximum slip is 3.39 m, the main fracture is located in the depth range of 0−10 km, the east side of the overall fracture is larger than the west side, the slip distribution is more uniform and smoother than Model A, and the inversion effect is good. ② The stress distributions calculated by different models are basically the same. The area of co-seismic Coulomb stress loading along the fracture segment increases with the depth, and there are both two distinct Coulomb stress loading areas at the west and east ends of the seismogenic fault zone. Significant stress loading occurs in the east and west sections of Kunlunshankou-Jiangcuo fault, Garze-Yushu fault, east section of the East Kunlun fault, Madoi-Gander fault, middle and west sections of Qingshuihe fault and west section of Dari fault. However, the Model B calculations differ, with the middle section of the Kunlunshankou-Jiangcuo fault in a state of stress unloading at the location. The fault stress state did not change much in the 10 post-seismic years, but the eastern section of the Qingshuihe fault had more significant stress unloading in the post-seismic stress adjustment, and the seismic hazard was reduced. ③ In order to explore the impact of strong earthquakes on Madoi earthquake, this paper calculated the co-seismic and post-seismic effects of the M≥7.0 strong earthquakes in Bayan Hara block after the 2008 Wenchuan earthquake on the stress loading and unloading of Madoi earthquake respectively. The results show that the Madoi earthquake is subject to strong earthquake loading, but it does not exceed the trigger threshold.