InSAR Measurements and Viscoelastic Modeling of Sinkhole Precursory Subsidence: Implications for Sinkhole Formation, Early Warning, and Sediment Properties

During the past three decades, thousands of sinkholes were formed along the Dead Sea (DS) shorelines in Israel and Jordan, due to dissolution of subsurface salt by undersaturated groundwater. The sinkholes are associated with gradual subsidence preceding their collapse by periods ranging from a few days to almost 5years. To determine the factors controlling this precursory subsidence, we examine tens of subsidence-sinkhole sequences along the DS shorelines in Israel. The duration and magnitude of the precursory subsidence are determined by Interferometric Synthetic Aperture Radar (InSAR) measurements and simulated by viscoelastic damage rheology models. Longer periods of precursory subsidence are found in the cemented alluvial fans and in simulations of higher-viscosity sediments. While surface subsidence accelerates during the precursory period, the widths of the subsiding areas remain uniform, suggesting that during this period upward propagation of damage from the subsurface cavity is not accompanied by upward migration of the actual cavity. Our observations and simulations are used to constrain the viscosity of the sediments along the DS and to reduce sinkhole hazards by assessing the precursory times of future sinkholes in the different sedimentary environments. Plain Language Summary During the past three decades, thousands of sinkholes were formed along the Dead Sea (DS) shorelines in Israel and Jordan, due to groundwater dissolution of a subsurface salt layer. The sinkholes are associated with gradual subsidence preceding their collapse by periods ranging from a few days to almost 5 years. To determine the factors controlling this precursory subsidence, we examine tens of subsidence-sinkhole sequences along the DS shorelines in Israel. The duration and magnitude of the precursory subsidence are determined by radar measurements taken every 16 days by the Italian Space Agency COnstellation of small Satellites for the Mediterranean basin Observation (COSMO) SkyMed satellites and then compared to simulations of deformation above a subsurface cavity in the salt layer, testing different cavity depths and sediment properties. Longer periods of precursory subsidence are found in the consolidated sediments and in simulations of the higher-viscosity sediments. The agreement between the observed and simulated duration of the precursory subsidence is used to constrain the mechanical properties of the sediments along the DS and to reduce sinkhole hazards by assessing the precursory times of future sinkholes in the different sedimentary environments.