Illuminating co-seismic deformation and seismogenic structures by combined 3-D seismic imaging and InSAR analysis: a case study from the Qaidam Basin, northern Tibetan Plateau

Understanding the relationship between co-seismic deformation and seismogenic structures is usually impeded by limited knowledge of underground deformation. We herein attempt to precisely establish the relationship through a case study of 2019 Mangya Earthquake in the Shizigou anticline, western Qaidam Basin (northern Tibetan Plateau) based on multiple datasets. Three-dimensional seismic imaging reveals complicated underground structures, including a shallow thrust, a deeply-buried reverse fault, and an intervening salt-bearing weak layer. The InSAR geodesy reveals co-seismic surface folding in the northeastern limb rather than the core of the anticline. Elastic inversion suggests a likely underground co-seismic slip surface at depth of ~2.1 km. They together indicate that Mangya Earthquake was caused by neither the shallow thrust nor the deep reverse fault; instead, it likely resulted from bed-parallel slip caused by local salt flow. Our findings demonstrate that complicated seismic behavior in structurally complex regions could be resolved by illumination of seismogenic structures.