The Dead Sea sinkhole hazard - new findings based on a multidisciplinary geophysical study
Résumé
A geophysical study has been carried out in the Dead Sea (DS) coastal area of Israel and Jordan with the goal of better understanding the development of sinkholes in the area. The following surface geophysical methods have been applied: (1) Seismic Refraction method for mapping the buried salt formation; (2) Microgravity and Magnetic Resonance Sounding (MRS) for detecting cavities in the subsurface; (3) Transient Electromagnetic method (TEM) for estimating groundwater salinity. It has been found that: (1) sinkholes have formed within a strip 50-100 m wide along the salt formation edge; (2) a zone with a large density of cavities with a total volume of tens of thousands of cubic meters have been inferred in sinkhole sites; (3) cavities underlying sinkholes are filled with unconsolidated sediments locally reducing hydraulic conductivity. Further development of new cavities has not been detected; (4) groundwater salinity variations along the DS shore are insignificant and changes in the electrical conductivity of the groundwater obtained using TEM were in most cases related to changes of porosity caused by collapse of subsurface sediments. (5) the applied geophysical methods provide valuable data on the development of sinkholes in the DS coastal areas.