Continuous monitoring of ground motion using Sentinel-1 InSAR time series: A case study from Doha, Qatar

An operational ground motion monitoring system was developed using Sentinel-1 data and applying Persistent Scatterer Interferometry (PSI). The automated system involves (1) downloading of archived Sentinel-1 data and orbital correction files, (2) extracting deformation products using archived Sentinel-1 data at full-resolution and applying the PSI method, (3) updating deformation products every 48 days with newly acquired Sentinel-1 images, and (4) disseminating the results through an interactive web-based GIS application. The system was implemented over Doha city in Qatar, which has been experiencing rapid urbanization, land use change, and groundwater level variations (i.e., dewatering, injection) over the last decade. The study investigates the impact of these anthropogenic activities on ground motion together with those of natural forcings. Initial ground motion products (line-of-sight [LOS], quasi-vertical, and quasi-East-West) were extracted from the archival Sentinel-1 data (Mar. 2017 Mar. 2021; 123 ascending and 107 descending scenes). The products were made publicly available online (https://www.esrs.wmich.edu/webmap/qatar) and are being updated every 48 days. The extracted initial rates were validated using continuous GPS stations. The factors controlling the observed ground motion were investigated by conducting spatial and temporal correlations of the ground motion products with relevant datasets (e.g., groundwater levels, land use, multi-temporal optical imagery, and distribution of subsurface openings such as caves, sinkholes, metro construction locations). Findings include: (1) high subsidence rates (up to 35 mm/yr) over landfills and dumpsites, (2) moderate subsidence rates (up to 10 mm/yr) over recently constructed industrial and residential buildings, (3) ground motion (up to 12mm/yr) associated with slope instability in a golf course, (4) localized subsidence (up to 5 mm/yr) over several land reclamation areas, and (5) uplift (up to 20 mm/yr) over the sabkha areas. The established system is expected to monitor ground motion continuously at the site and potentially detect other issues related to infrastructure, sinkhole formation, and groundwater management practices in the future.