Distributed deformation characteristics near faults during strike-slip earthquakes

The coseismic fault damage zone is a region of nonelastic permanent deformation along a fault during an earthquake. It consists of localized dislocation deformation and peripheral distributed diffuse deformation. Diffuse deformation consists of microcracks and other features, and thus is difficult to observe directly. It requires imaging geodetic techniques for detection. However, in high-gradient deformation zones near the fault rupture trace, InSAR often suffers from decorrelation. It leads to gaps in deformation measurements. This study uses the Pixel Offset Tracking (POT) technique, which is based on SAR backscatter intensity to capture near-fault large-gradient deformation from several strike-slip earthquakes (eg. 2019 Mw7.1 Ridgecrest earthquake, the 2021 Mw7.4 Maduo earthquake,  the 2022 Mw6.7 Menyuan earthquake). We quantitatively analyzed the width and magnitude of the distributed diffuse deformation within the seismic fault damage zone. Results show that distributed deformation spreads hundreds of meters to several kilometers from the fault on both sides. The width of the fault damage zone shows similar trends along the fault strike, with significant increases in geometrically complex areas (fault bends, branches, stepovers, and secondary faults). The destructive effect of diffuse deformation is less abrupt than dislocation deformation. However, it still shows considerable deformation gradients. Moreover, its spatial extent often far exceeds that of dislocation-type deformation. This leads to substantial economic and human losses. Therefore, summarizing distributed deformation patterns in large earthquake fault damage zones is important. It provides both a theoretical foundation and technical support for engineering seismic design.