The very low‐frequency step‐frequency GPR system and its application to active fault detection

Abstract

ABSTRACTGround‐penetrating radar (GPR) in the high‐frequency range is subject to attenuation, which limits its application in many fields, such as underground water detection and other near‐surface geological studies. We built a very low‐frequency GPR system based on a vector network analyser (VNA) and developed the system controlling software using visual basic for application (VBA). We also built a wire‐line antenna with a central frequency of 10 MHz on the ground. Results from an experiment on a water reservoir dam showed that the system works well.Active fault evaluation is important for city planning and construction. The soil layer in Changchun City, Northeast China, has low‐resistivity and a depth of 10–20 metres. It is difficult for conventional GPR systems to detect bedrock in Changchun City. In this paper, we investigate the active fault in Changchun City using the very low‐frequency step‐frequency GPR system. The results from the step‐frequency GPR shows clearly the undulation of the bedrock. From this and the resistivity soundings we are able to interpret the location and the depth of the fault.