Near-Surface Seismic Refraction Tomography; a case study for geotechnical application

Abstract

Usually, among geophysical techniques, seismic refraction methods are used to investigate near surface geology for engineering purposes. In these study physical parameters, longitudinal seismic wave velocities were used to characterize the shallow subsurface layers for geotechnical application.  The physical response of subsurface materials varies as the structure, porosity, fluid saturation, composition and tie-up vary. These variations primarily viewed in the first arrival time of seismic waves. With the necessary steps, the first arrival waves were inverted to get the seismic velocity model of the area. It has three layers, having an increasing velocity with depth. From the seismic velocity models, the area is covered by low-velocity materials (soil) extend to a maximum of 8 m thickness underlie with phreatomagmatic deposits. The third layer, located at an average depth of 15 m, has undulated topography, welded pyroclastic rocks with average seismic velocities of 2.4 km/s and it is recommended that the base of the foundation should be a tie with this layer.