Investigations of the shallow bedrock using the seismic refraction method – A case study in New Qena City, Eastern Desert, Egypt

Abstract

The seismic refraction technique has demonstrated its efficiency as a cost-effective geophysical approach for bedrock investigation, which is very important for major construction projects. In the eastern part of New Qena City, along Qena-Safaga Road in the Eastern Desert of Egypt, construction of many domestic facilities is planned. Therefore, a prior site investigation focusing on bedrock is required to validate the site for construction and other projects. In this study, a site investigation of the eastern part of New Qena City is conducted using the seismic refraction method to estimate the depth and thickness of the bedrock and to present the surface structural features affecting the area. Ten seismic refraction profiles were measured in the area. The results of tomographic modeling show that the bedrock consists of three layers, with the bedrock represented by the mudstone unit of the Pliocene Durri Formation. This layer is located at a shallow depth and varies in thickness in the area. The seismic velocity sections show that the layer is characterized by relatively low velocities as well as lateral velocity variations. This is interpreted to be due to the clay content of the layer, the high degree of fracturing, and the lateral facies variation. Therefore, the layer could undergo geotechnical problems that could affect future construction projects in the area. Four subsurface faults were also detected in the velocity sections created by the tomographic inversion.