Detecting infrastructure hazard potential change by SAR techniques on postseismic surface deformation: A case study of 2016 Meinong earthquake in southwestern Taiwan

Abstract

Over the past two decades, multi-temporal InSAR techniques have been successfully utilized to monitor surface deformation throughout earthquake cycles. As sensor resolution and observation frequency of radar satellites have significantly improved, the spatial monitoring capability has expanded from tectonic to regional and local scales. Although regions with higher deformation rates are generally considered to have greater hazard potential, from an engineering perspective, locations with abrupt displacement rate changes may pose greater risks. This paper presents a robust method to transform tectonic-scale geodetic data into engineering-scale deformation tolerance ratios for assessing infrastructure safety during the postseismic period. Using the persistent scatterer InSAR (PSI) method, we measured line-of-sight (LOS) displacements from Sentinel-1 satellite images. By correcting LOS velocities with GNSS data and constraining the velocity in the N-S direction, we inverted the 2D (E-W and UD) postseismic deformation rates for the three years following the 2016 Meinong earthquake. The 2D rates were then converted into annual deformation tolerance ratios (ADTR), with a statistically established threshold to identify infrastructure segments with high hazard potential. Additionally, we conducted time-series variation analysis on the inherent pixel unit to evaluate the state of hazard potential and characterize the spatiotemporal behavior of fault systems during the postseismic period. Our results indicated that the postseismic deformation rates in the E-W and UD directions are 1.5 and 2–3 times higher, respectively, than those in the interseismic period. The horizontal ADTR index of high-speed railway infrastructures identified a high-hazard potential segment located on the Chegualin fault in Kaohsiung, while the vertical ADTR index highlighted a high-hazard potential segment at a junction between multiple fault extensions in Tainan. Moreover, statistical time-series variation analysis revealed a gradual decrease in hazard potential after 2017, which is related to a slow earthquake that occurred in early to mid-2018, modulating regional stress during the postseismic period. Our novel method not only highlights the impact of postseismic deformation on infrastructure but also provides a crucial basis for future earthquake hazard prevention and mitigation.