Feasibility of Detecting Near-Surface Cavities Using Integrated Seismic and GPR Techniques

Abstract

The feasibility of directly detecting near-surfaces cavities is challenging due to the complexity of nearsurface materials and the limited resolution of seismic techniques. Therefore, Shallow seismic survey has been applied for an area of limestone rocks includes subsurface cavity at depth about 3 meters under the ground surface. seismic waves have been generated and acquired with high resolution and good quality characteristics along profiles passing through the cavity with 1 meter geophone spacing and multi-channels seismograph. During a comprehensive sequence of data processing and using more sophisticated software for refraction tomography and multi-channel analysis of surface waves (MASW ) , the cavity has detected at about 3 meters depth and about 30 meters of lateral extension has been clearly identified. Furthermore, the location of the cavity has been confirmed successfully through the application of GPR surveying profiles along the inspected cave position. The acquired GPR profiles are processed and filtered to minimize the noise effects. High amplitude reflections are observed within the profile. These high amplitude reflections are good indicator to the presence of cavity at a depth of 3 meters from the earth's surface with thickness of about 8 meters and extend laterally for about 30 meters in the profile direction. It noticed that both of lateral extension and depth to the top of the cavity have been identified through seismic and GPR data interpretation. It is concluded that, the integration between two different near surface geophysical techniques is powerful and helpful way in detecting not only the depth for the subsurface features but also in determining their lateral dimensions.