IDENTIFYING NEAR SURFACE SALT DIAPIRS IN ARID ENVIRONMENTS USING OPTICAL AND RADAR REMOTE SENSING

Salt diapirs are commonly investigated for their potential role as oil and gas traps; in this study, surficial and near-surface salt domes within Jazan City in southwest Saudi Arabia and surroundings, are investigated as an environmental hazard. Within the city and proximal to the arid coastline, a salt diapir crops out over an area of 1.5 km² forming a domal structure. The dome rises some 40 meters above the surrounding flat Jazan coastal plain and is composed of a chaotic mix of lithologies from the cap rock and overburden sediments (i.e., anhydrite, gypsum, shale, sandstone). The continuing deformation associated with the salt diapir intrusion compromises the integrity of pre-existing structures and limits the expansion of cities along the Red Sea coastline. Using optical and radar data acquired over the Jazan salt diapir, we identified characteristics indicative of near-surface salt diapirs and used the criteria to delineate potential locations of diapirs within the study area. False color composites were generated from individual bands and band-ratio images in the VNIR and SWIR wavelength regions that are sensitive to vibrational absorptions in the 1000 to 2500 nm wavelength region. Both ASTER [30m] and DigitalGlobe’s commercial WorldView-3 superspectral satellite (8 multispectral [spatial resolution: 1.24m] and 8 short-wave infrared bands [spatial resolution: 7.5m]) imagery were used. Small Baseline Subset (SBAS) and Persistent Scatterer (PS) Radar interferometric techniques were used with ESA’s C-band radar satellites (Envisat: 2003 to 2009; Sentinel-1A: 2014 to 2018). Uplift rates of up to 4 mm/yr were detected over the center of the Jazan diapir. Three areas were identified as potential locations for surficial and subsurface diapirs as they show evidence for uplift and/or spectral characteristics similar to those observed over the Jazan diapir: (1) area A: (lat 16º51’40”, long 42º35’24”); 2 km²; uplift rates up to 5 mm/yr; (2) area B: (lat 16º49’12”, long 42º38’19”); 1 km²; uplift rates up to 4 mm/yr; and (3) area C: a cluster of three domes: (lat 16º41’50”, long 42º42’44; 0.5 km²). The identified locations will be drilled to verify if salt is present and at what depths.