A Persistent Scatterer Interferometry-Based Parametric Framework for Characterizing Pre-, Co-, and Post-Seismic Surface Deformation: Application to the 2025 Dingri Earthquake (Southern Tibet)

Persistent Scatterer Interferometry (PSI) provides dense and temporally continuous measurements of ground deformation, offering a robust framework for investigating, among other phenomena, earthquake-related surface deformation. However, most satellite-based investigations of large earthquakes remain focused on coseismic interferograms, source inversions, and short post-seismic observation windows. In this study, we propose a PSI-based parametric approach that, given a Persistent Scatterer (PS) time series, uses a piecewise linear regression with an imposed coseismic step at the earthquake origin time to estimate the pre-event line-of-sight (LOS) velocity, the coseismic displacement step, and the post-event LOS velocity using ascending and descending satellite observations. The methodology is applied to the 7 January 2025 Mw 7.1 Dingri earthquake (southern Tibet), a recent large normal-faulting event for which previous studies have documented complex rupture behavior and significant co- and post-seismic surface deformation. The results show that our PSI-based approach enables, within a single framework, the isolation of the coseismic jump, the quantification of post-event velocity patterns, and the systematic comparison of pre- and post- event deformation. In addition, the combination of ascending and descending datasets yields a first-order reconstruction of the vertical and east–west deformation components. The proposed approach complements physics-based source modeling by offering a scalable, observation-driven, and point-wise characterization of deformation evolution.