Red Sea faulting and salt diapirism as a potential geotechnical hazard in Jazan, southwest Saudi Arabia: inferences from gravity data

The main objective of this study is to detect the subsurface extension of salt diapirs and structural deformations in the city of Jazan and its suburbs using gravity data. Salt diapirs are of economic importance, but they can also be geologic hazards. Our results show weak Bouguer anomalies at Jazan Port and Jazan Heritage Village, suggesting the intrusion of near-surface salt diapirs. These anomalies are not observed in regional gravity maps, indicating shallow depths of the interpreted salt diapirs. Edge-detection gravity maps clearly reveal that NW–SE and NE–SW trending fault systems dissect the area. The NW–SE trending faults dissect the city into a series of faults and tilted blocks that generally dip toward the Red Sea, and which are crosscut by a NE–SW transform shear zone at Jazan Heritage Village. The interpreted salt diapirs are controlled by rifting since the Miocene. It is suggested that the salt diapirs migrated vertically through the walls of NW-trending fault blocks to reach the surface in the old city of Jazan. The salt diapirs extend eastward, facilitated by lateral movement along the NE transform fault until they are stopped by the NW-trending uplifted blocks in the western side of the city. The interpreted halokinesys and faulting structures may be a potential geotechnical hazard that could affect the infrastructure and urban buildings in Jazan and its suburbs.