Date of Award

12-2020

Degree Name

Doctor of Philosophy

Department

Geological and Environmental Sciences

First Advisor

Dr. Mohamed Sutlan

Second Advisor

Dr. William Sauck

Third Advisor

Dr. Alan E. Kehew

Fourth Advisor

Dr. Racha El Kadiri

Keywords

Gravity, passive seismic, salt diapirs, land deformation, Saudi Arabia

Abstract

Salt diapirs are rarely preserved on the surface and seldom considered as environmental hazards. The Jazan city diapir (JZD) is located in southwest Saudi Arabia along the Red Sea coastal plain and outcrops in the middle of a rapidly growing port city. The intrusion of the diapir (~ 2 km2) into the overburden sediments continues to cause uneven surfaces, compromises building foundations and infrastructure, caused dissolution sinkholes, and limits the expansion of the city along the coastline. This research aims to better understand the distribution and deformation associated with salt diapirs in arid environments.

Using integrated Interferometric Synthetic Aperture Radar (InSAR) datasets (Envisat: 2003–2009; Sentinel-1: 2014–2018), local and regional gravity surveys, and passive seismic data, the environmental hazards associated with the rise of the Miocene JZD were investigated, and areas at risk in its immediate surroundings were identified. Drilling, field investigations, GPS, and optical remote sensing data were used to calibrate and validate the radar-based velocities and distribution of the diapir. The findings include: (1) the JZD outcrop and its northern, southern, and western bordering areas have been undergoing substantial uplift (up to 4.7 mm/yr), whereas the surrounding sabkhas are witnessing subsidence (up to −7.5 mm/yr); (2) a low relative Bouguer anomaly was observed over the JZD with the steepest gradient along its eastern side; (3) strong and clear horizontal/vertical (H/V) spectral ratio peak and high frequency (5–10 Hz) over the JZD outcrop and areas proximal to its western margin, but areas to the east have a weak H/V peak and low frequency (1.5-3 HZ); (4) drilling confirmed the presence of a shallow (4 m) salt bedrock layer west of the JZD, and the absence of this layer to the east (up to depths of 60 m); (5) uplift patterns along the diapir margins are indicative of near-vertical contact along the JZD eastern margin and less steep contacts along the remaining margins; (6) the presence of rising diapirs proximal to the shoreline and their apparent absence inland could be related to their preservation in areas affected by sea water intrusion; and (7) additional near-surface diapirs could potentially be identified in the vicinity of the JZD using the above integrated approach.

Access Setting

Dissertation-Open Access

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