关键词: 青白江Ms 5.1级地震, 地震反射剖面, 地震重定位, InSAR同震形变, 龙泉山断裂带

Abstract: On February 3, 2020, an Ms 5.1 earthquake occurred in Qingbaijiang District, Chengdu City, Sichuan Province, with the epicenter located in the northern part of Longquanshan fault zone of the Western Sichuan Basin. There are east and west branch faults in the north part of Longquanshan fault zone, the seismogenic fault, earthquake genesis and power source of this earthquake are not clear at present, which makes it difficult to deeply analyze and evaluate the potential earthquake risk in Longquanshan area. In this study, the multiple constraint method was used to comprehensively study the Qingbaijiang Ms5.1 earthquake through geophysics, seismology, geodesy, combined with structural geology and fault-related fold theory. In this paper, the basic structural features of the epicenter are revealed by using the artificial seismic reflection profile, there is a combination of a back-thrust fault and a thrust fault developed on the regional detachment layer of middle -lower Triassic. The result of seismic relocation shows that the focal depth is 5 km, which indicates that the earthquake is related to the activity of shallow faults. The aftershock relocation is mainly distributed near the east branch of the north Longquanshan fault zone, and the occurrence of the east branch is consistent with the focal mechanism solution. The coseismic deformation field of InSAR near the epicenter is extracted, and the maximum coseismic deformation is 4cm; the deformation caused by the earthquake is uplift in the northwest of the epicenter and depression in the southeast, which is in line with the characteristics of thrust activity of the east branch of the north Longquanshan fault zone. In this study, through multidisciplinary and multiple constraints, the Qingbaijiang Ms 5.1 earthquake structure in 2020 is analyzed in detail, the seismogenic fault is determined, and the possible seismic dynamic background is discussed, which provides a certain basis for fault activity analysis and seismic risk assessment in Longquanshan area.

Key words: Qingbaijiang Ms 5.1 earthquake, seismic reflection profile, seismic relocation, InSAR coseismic deformation field, Longquanshan fault zone