Systematic Comparison of InSAR and Seismic Source Models for Moderate‐Size Earthquakes in Western China: Implication to the Seismogenic Capacity of the Shallow Crust

Abstract

Earthquake source parameters are important for understanding earthquake physics and crustal fault properties. However, strong trade‐offs between parameters (e.g., depth and origin time) and a lack of accurate velocity models and near‐field seismic stations could cause large uncertainties of these parameters in seismic catalogs, particularly for shallow events. To further improve the resolution of earthquake source parameters, we use Interferometric Synthetic Aperture Radar (InSAR) images to derive source solutions of 33 moderate‐size (Mw 4.1–6.6) earthquakes that occurred at shallow depths (<20 km) from November 2014 to July 2020 in western China. After evaluating the uncertainties of the InSAR solutions, we systematically compare the location, centroid depth, focal mechanism and magnitude from InSAR models with that from seismic catalogs. We find that all seismic catalogs generally report deeper (4–10 km) hypocenters or centroid depths. The uncertainties of moment tensor solutions are partially related to the percentage of the non‐double‐couple components in the seismic catalogs. The InSAR solutions indicate that considerable seismic moments (i.e., ∼2×1018 ${2\times 10}^{18}$ Nm) were released in the uppermost crust (i.e., <5 km) in a period of ∼6 years, which is not resolvable in the seismic catalogs. The smooth seismic moment distribution along depth indicates a gradual change of the frictional properties from the surface to the middle crust. As most of the studied earthquakes are located on secondary and/or unmapped faults, these findings imply a considerable portion of velocity‐weakening friction in the uppermost crust along immature, secondary fault systems, which should be included in the seismic hazard evaluation.

Kinematic Slip Evolution During the 2022 Ms 6.8 Luding, China, Earthquake: Compatible With the Preseismic Locked Patch

“…The differences in earthquake source parameters from the Global CMT, CENC, and USGS are not trivial and are intrinsically related to the inversion approaches, station coverage, and seismic velocity model (Duputel et al., 2012; Ekström et al., 2012). Geodetic crustal deformation with positioning accuracy and high spatial resolution could provide independent constraints relative to the seismic data, which can pin down the earthquake horizontal location much closer to the ground truth in comparison to the seismological solutions, especially for earthquakes with no significant surface rupture (e.g., Elliott et al., 2016; H. Luo et al., 2022; Jiang et al., 2014). Due to the complementary nature between seismic and geodetic data, the joint inversion of these two datasets can retrieve more robust and detailed information on the source parameters, which has been demonstrated in a wide range of applications (e.g., Guo, Zheng, An, et al., 2020).…”