Use of GPR method for prediction of sinkholes formation along the Dead Sea Shores, Israel

Abstract

It seems the highly saline conditions of the Dead Sea (DS) coast line are not favorable for the use of Ground Penetrating Radar (GPR) method for detection of underground caverns before sinkhole formation (short-time prediction). The location of the formed caverns within the salt layer (significantly more than the penetration depth of the electromagnetic waves) combined with the saline DS brine (groundwater) covering the salt layer from above, characterized by low electrical resistivity, makes the application of electromagnetic waves (EW) impossible. However, our experience has shown that GPR technique in its 2D and 3D modifications can be a very efficient tool to predict sinkhole susceptibility. Case histories of GPR studies in the Mineral Beach and Nahal David sites are presented. The GPR study has shown that the method is effective in both urban sites and at most of sites of human activities of the Dead Sea coast (dwellings, routes, agricultural areas etc.), but it fails in areas composed of saline mud in the subsurface (some areas lower than −400 m elevation). The fan areas are composed of sandy-gravel sediments and the penetrating depth of the electromagnetic waves varies but is usually limited to the first meters up to 8–10 m (maximum to 13–15 m), but in any case not deeper than the water table (depending on the dielectric constant, which as a rule is 4–25). In areas covered by Dead Sea mud, penetration depth is limited to the first meter due to the low electrical resistivity of the sediments. Models of sinkhole formation and principles of cavity detection in the DS area are discussed to understand the fundamentals of GPR use for the prediction of sinkhole susceptibility.