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EARTHQUAKE ›› 2021, Vol. 41 ›› Issue (2): 1-13.doi: 10.12196/j.issn.1000-3274.2021.02.001

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Study on Seismogenic Structure of the Yutian MS6.4 Earthquake in Xinjiang in 2020

GENG Shuang1, WANG Lin1, TIAN Qin-jian1, XU Yue-ren1, LI Wen-qiao1, YUAN Zhao-de2   

  1. 1. Institute for Earthquake Forecasting, China Earthquake Administration, Beijing 100036, China;
    2. Institute of Geology, China Earthquake Administration, Beijing 100029, China
  • Received:2021-01-19 Revised:2021-02-23 Published:2021-08-06

Abstract: The Yutian MS6.4 earthquake, which occurred on 26 June 2020 in West Kunlun, Xinjiang, is another strong earthquake following the 2008 MS7.3 and 2014 MS7.3 earthquakes. Determination of the seismogenic structure of this earthquake is a basic problem to be solved for seismic anatomy. Based on GIS platform and technology, this paper fully integrates various data such as structure geology, high-resolution remote sensing, topography, seismology, GPS velocity field and focal mechanism. The dynamic and kinematic mechanisms related to earthquakes are studied, and the seismogenic structure is preliminarily determined. The Yutian earthquake may be the result of a further southwest rupture of the ruptured segment of the 2014 strong earthquake. The results of seismic relocation show that the epicenter is located near Ulugh Muztagh. The results of high-resolution remote sensing interpretation and tectonic geomorphology deformation analysis show that the epicentral area is a typical extensional basin-ridge tectonic area, and there are small faulted basins and basin-controlling normal faults. High resolution satellite images after the earthquake showed that no obvious surface rupture zone and secondary earthquake disasters were found in the earthquake area. This earthquake may be caused by the activity of the NE-trending tectonic system in the tectonic belt between the West Kunlun block and the Songpan-Ganzi block. Due to the oblique tension movement of the blocks on both sides of the structural belt, normal faults and strike-slip faults are successively formed and continuously and synchronously faulted in the structural belt. Normal faults are more active than strike-slip faults in the area. Normal faults and strike-slip faults can well adapt to and absorb the tensile pure shear component and the lateral simple shear component respectively, so that normal faults and strike-slip earthquakes occur frequently in the tectonic belt. There may be a multi-level extensional tectonic system in the crust from the surface to the deep, and there may be no obvious correlation between the various systems. This earthquake may have little relationship with the surface tensional structural system, and it is inferred that it is the result of the activity of deep-seated tensional structural system.

Key words: The Yutian MS6.4 earthquake in Xinjiang in 2020, Seismogenic structure, High-resolution remote sensing, Tectonic block movement

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