Measuring and Monitoring Land Subsidence and Earth Fissures in Al-Qassim Region, Saudi Arabia: Inferences from InSAR

Abstract

Numerous land deformations (land subsidence and fissures) events have been reported from the Central part (Al Qassim) of the Kingdom of Saudi Arabia. An integrated approach (geo-informatics, geologic, and hydrogeology) is adapted to identify areas threatened and affected by land deformations, and also to evaluate the causes of these phenomena. A fourfold approach is applied in this research including; (1) Conducting field visits to collect observations, (2) Constructing spatial correlations in a GIS for the damaged locations which related to the registered spatial datasets (surface and subsurface geology) and temporal datasets (e.g., land use, groundwater extraction, distribution, depth and magnitude of earthquakes), (3) Extracting deformation rates (subsidence) using SBAS radar inter-ferometric technique using ENVISAT data sets, and (4) Correlating the extracted subsidence rates spatially and temporally with GRACE mass variations data. The SBAS investigation revealed high subsidence rates (−5 to −12 mm/yr) along a NW-SE direction, with some subsidence (−2 to −4) in the southwestern part of the study area. This subsidence is correlated with areas witnessing a huge drawdown in the fossil groundwater levels and a depletion in GRACE-derived TWS. Most earth fissures are located around the margins of the subsiding areas and are caused by bending beam activities surrounding the subsiding lands.