Abstract:We analyze the characteristics of fault structure and tectonic deformation in the middle-east section of Qilian mountain based on the relocation results of small and medium earthquakes and geophysical data of stress field. The results show that: 1) The focal depth of the middle-east section of Qilian mountain is 2-20 km. The focal depth distribution of the Longshoushan fault is an inverted triangle with a wide upper and narrow lower. The aftershock depth of the Menyuan MS6.4 earthquake is 5-15 km, with a tendency of SW. The eastern section of Jinqianghe fault has strong seismicity, with a tendency of NE and high dip angle. The eastern section of Laohushan fault is highly seismically active, with a tendency of NE and a near vertical occurrence in its depth. The focal depth of the middle-east section of Qilian mountain increases gradually from west to east. It is speculated that deeper tectonic activity may have occurred in the eastern Qilian mountains. 2) The direction of principal compressive stress in the study area is NE-NEE. 3) The combined fracture of a series of strike-slip faults and front thrust faults along the middle-east section of Qilian mountain is an important structural deformation regulation mode for the NE extrusion of the Qinghai-Tibet plateau.
ZHOU Lin,LI Zhangjun,LI Jun et al. Study on Fault Structure and Tectonic Deformation Characteristics of the Middle-East Section of Qilian Mountain[J]. jgg, 2022, 42(6): 565-568.