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EARTHQUAKE ›› 2021, Vol. 41 ›› Issue (4): 93-105.doi: 10.12196/j.issn.1000-3274.2021.04.007

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Study on the Focal Mechanism of the 2020 Qiaojia M5.0 Earthquake and the Stress Field in the Epicentral Area

YANG Fan1, SHENG Shu-zhong2, HU Xiao-hui3, CUI hua-wei4   

  1. 1. Yunnan Earthquake Agency, Kunming 650224, China;
    2. State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, Nanchang 330013, China;
    3. University of Science and Technology of China, Hefei 230026, China;
    4. Shandong Earthquake Agency, Ji’nan 250102, China
  • Received:2021-02-20 Revised:2021-06-16 Online:2021-10-31 Published:2022-03-25

Abstract: Based on the digital waveform from Data Management Centre of National Seismic Network, the focal mechanism solutions of the May 18, 2020 Yunnan Qiaojia M5.0 earthquake and 51 historical earthquakes in the focal area were inverted by using gCAP method, and collect 50 focal mechanism solutions in the study area. Wan’s grid search method is used to invert the tectonic stress field in the seismic source area, and the study area is divided into different divisions for stress field inversion. The results show that: ① the mainshock parameters are as follow, nodal plane I: strike=175°, dip=67°, rake=-19°; nodal plane Ⅱ: strike=273°, dip=73°, rake=156°, the moment magnitude is 4.97, centroid depth is 8.8 km, focal mechanisms represent that the Qiaojia earthquake is a strike-slip event with thrust component. ② The orientation of maximum principal compressive stress axis is NWW in nearly horizontal direction; the orientation of minimum principal compressive stress axis is NNE in nearly horizontal direction; the stress field in source region shows a strike-slip stress regime. ③ The stress field results obtained from the division of different regions are not much different, indicating that the stress field in this region is relatively stable, and is less affected by the type of deep and large faults and focal mechanism solutions.

Key words: 2020 Qiaojia M5.0 earthquake, Focal mechanism, Tectonic stress field

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