Deep seismogenic tectonics of Yangbi Ms6.4 on 21 May 2021 in the SE margin of the Tibetan plateau from earthquake sequence relocation, stress field and seismic anisotropy
Deep seismogenic tectonics of Yangbi Ms6.4 on 21 May 2021 in the SE margin of the Tibetan plateau from earthquake sequence relocation, stress field and seismic anisotropy
复制标题
从地震序列重定位、应力场和地震各向异性分析2021年5月21日青藏高原东南缘漾濞Ms6.4深部发震构造
DOI：
10.1016/j.tecto.2023.229768
复制
发表时间：
2023
期刊：
影响因子：
2.9
通讯作者：
Yan Luo
中科院分区：
文献类型：
--
作者：
Jianhui Tian;Yuan Gao;Yan Luo
2021年5月21日，云南省中国杨碧县发生6.4级地震。地震位于青藏高原东南缘川滇块体西部边界红河断裂的西侧。洋壁6.4级地震因其独特的地理位置和云南强震频发而备受关注。利用双差定位方法，对杨壁6.4级地震序列的4 695个震源位置进行了重新定位，其中主震震源位置为东经99.879°，北纬25.687°，震源深度9.67亿千米。主震的阶矩震级为6.1级，其中一个断层面解的走向为13 7°，倾角为83°，−为16 3°。结合定位解和震源机制解结果，认为杨壁6.4级地震的发震断裂为魏西-桥侯断裂(WQF)西南侧的NW-SE向断裂，具有较高的南西倾角，是一条未知的隐伏断裂。区域二维应力场显示，羊壁地震周围的主压应力方向为NNW-SSE和近N-S方向，其东侧为逆时针方向的小角度偏转，西侧为N-S和NNE-SSW向，而羊壁地震南北两侧具有方向一致性。构造应力场和地震各向异性反映了震源东北方向上地壳强烈的差异变形，反映了丽江-小金河断裂(LXF)的强烈影响。震源区应力场受青藏高原东南缘的东南向运动、印度板块的北东向运动和不同构造块体之间的差异运动共同控制。
TheMS6.4 earthquake occurred in Yangbi County, Yunnan Province, China, on 21 May, 2021. The earthquake is located on the west side of the Red River fault, the western boundary of the Sichuan-Yunnan block in the SE margin of the Tibetan Plateau. The YangbiMS6.4 earthquake has aroused great concern due to its unique geographical location and frequent strong earthquakes in Yunnan. In this study, a total of 4695 local earthquakes of the YangbiMS6.4 earthquake sequence are relocated using the double-difference location method, including the mainshock source location of 99.879°E, 25.687°N, and depth of 9.67 km. The mainshock has a moment magnitude of 6.1, and one of the fault-plane solutions is 137°, 83° and − 163° in strike, dip, rake respectively. Combined with the relocation and focal mechanism solutions results, it is suggested that the seismogenic fault of the YangbiMS6.4 earthquake is a NW-SE trending fault on the southwest side of the Weixi-Qiaohou fault (WQF), with high dip of SW, which is a previously-unknown blind fault. The regional 2D stress field shows that the principal compressive stress around the Yangbi earthquake is NNW-SSE and nearly N-S direction, which appears to be deflected counterclockwise by a small angle on its east side and changed to N-S and NNE-SSW direction on its west side, while both the north and south sides of the Yangbi earthquake show directional coherence. Strong differential deformation distorts in the upper crust to the northeast of the seismic source as reflected by tectonic stress field and the upper crust seismic anisotropy, indicating strong influence of Lijiang-Xiaojinhe fault (LXF). The stress field in the source area is jointly controlled by southeastward movement of southeastern margin of Tibetan Plateau, the northeastward movement of Indian plate and the differential movement between the different tectonic blocks.