Study on deformation and structural characteristics of the M w 7.4 earthquake fault zone in Maduo, Qinghai Province by combining optical, InSAR and seismic data

Abstract

Abstract By means of D-InSAR and weighted least square method, the coseismic deformation field of the Mw7.4 earthquake in Maduo, Qinghai Province on May 22, 2021 was solved by using Sentinel-1A data of ESA. The horizontal deformation field of earthquake was extracted from Sentinel-2 optical data, and the vorticity field, divergence field, and shear strain field were introduced as operators to obtain the special surface deformation mode associated with surface rupture geometry. On this basis, the singular value decomposition algorithm was used to fit the point cloud data of the aftershocks so as to obtain the geometric structure parameters of the seismogenic faults. The fine structure characteristics of coseismic slip distribution were inverted with the constraint of InSAR deformation field in ascending orbit. The results show that the length of surface rupture trajectory of the Maduo earthquake reaches 166 km, and branch ruptures occur at both the head and the end. The movement of seismogenic faults is mainly left-lateral strike-slip; the main rupture occurs in the depth range of 0 ~ 10 km. There are 8 ruptured concave-convex bodies along the fault strike, with the maximum slip amount reaching 5 m, and the moment magnitude being Mw7.42. The area where static Coulomb stress increases on the seismogenic fault is consistent with the distribution of aftershocks, indicating that aftershocks are triggered by static Coulomb stress loading. Combined with field investigation, geological data and geodetic data, it is concluded that the seismogenic fault is a fault in its early evolution process, and the rupture of the main fault F3 may excite the immature F2 fault.