Delineation of Subsurface Structures using Seismic Refraction Tomographic Inversion in Wadi Al-Dawasir, South Saudi Arabia

The main objective of this paper is to delineate the subsurface structures, especially faults, in Al Haddar, Wadi Al-Dawasir area which is a part of the Sulayyimah Quadrangle, South Saudi Arabia using non-linear seismic refraction tomographic inversion. No major structures or faults are observed from the surface geological studies, while most of the area is covered with sand dunes and recent quaternary deposits. The purpose of the current research is to use the seismic method, which has been widely deployed in detecting and mapping subsurface features, to delineate the subsurface structures utilizing the 2-D seismic refraction travel-time tomographic inversion technique. The main advantages of travel time tomography are that it is a nondestructive technique, it provides a velocity model for the subsurface and delineates the subsurface faults with very high accuracy without involving drilling or trenching. The seismic data were acquired employing the most advanced and up-to-date instruments for high-resolution investigation. The system consists of the source, which is a vibrator (Vibroseis), sensors (receivers or geophones), and the acquisition system. A 40 Hz vertical geophone Model GS-20DH was used as the receiver, Strata Visor with geodes was put into service as the acquisition system, and end-on spread was installed by utilizing 112 geophones, while the source is offset 10 m away from the seismic line. The length of the acquired seismic line was 4.5 km. The final velocity tomogram is graphically presented as a 2-D grid of pixels, where each pixel contains the model parameters of interest such as the velocity value or its reciprocal value known as slowness. The travel-time tomography was able to provide a velocity model for the subsurface and delineate the subsurface faults with high accuracy.