Review of satellite radar interferometry for subsidence analysis

This paper includes a critical review of the existing literature on the use of satellite SAR imagery for subsidence analysis. Land subsidence, related to multiple natural and human-induced processes, is observed globally in an increasing number of areas. Potentially leading to severe impacts on economics and the environment, subsidence has attracted growing scientific attention and, over the last decades, new tools and methods have been developed for accurately measuring the spatial and temporal evolution of surface deformations associated with subsidence phenomena. The collection of the existing scientific literature on the satellite InSAR for subsidence analysis was conducted in January 2022 exploiting the WoS's freely accessible web search engine. An extensive database of 1059 scientific contributions was compiled, covering the period 1997–2021. The content of each record in the literature database has been critically examined to collect and store information regarding the study area location, microwave band adopted, satellite used, processing approach, subsidence cause, application type, field evidence and strategies to validate and compare InSAR data. Analysis of temporal distribution revealed a substantial growth in scientific production and an increasing interest of geoscientists, with a mean value of 21 articles per year from 1997 to 2014, rising to about 100 articles per year between 2015 and 2021. All continents include at least a study area, with Asia and Europe having the largest number of case studies, with 586 and 281 analyses in their territory, respectively, and revealing a clear geographical bias in subsidence study locations. Graphical visualizations and syntheses of current applications are presented. The large availability of different acquisition bands, the increasing imaging capabilities, refinement of processing approaches, and growing expertise in data interpretation allowed InSAR data to be used at different scales of analysis, for different purposes and subsidence types, in a wide range of physiographic settings. This review highlights that satellite InSAR has moved from being a niche topic to an operative tool with a major role in subsidence studies. Despite more than 25 years of progress and advancements, technical and operational challenges remain to be faced. Leveraging on the analysis of the literature review and authors' experience, recommendations and perspectives are provided for a more effective use of InSAR data.