Application of ground penetrating radar to investigation of the Wellington Fault (NZ)

A reliable investigation of the position and extension of active faults by nondestructive geophysical methods in urban areas is important to estimate seismic hazard. Ground-Penetrating Radar (GPR) is one geophysical method that can provide data similar to seismic reflection data. GPR is based on the propagation, reflection and scattering of high frequency (from 10 MHz to I GHz) electromagnetic (EM) waves in the subsurface (Davis and Annan, 1989). The vertical resolution and penetration of this method depend on the frequency band used and varies from a few centimeters to a few meters. Recent studies have shown how GPR can help locate previously poorly determined near-surface faults (Cai, McMechan and Fisher, 1996; Meyers et al, 1996; Liner and Liner, 1997). In March 1988, we undertook a series of GPR profiles at several sites around Wellington, New Zealand. The objectives of this study were to determine whether it is possible to obtain shallow geological information from GPR data and to show the applicability of GPR in locating active fault structures. The sites were chosen along part of the Wellington fault, situated in an urban area, where other geophysical techniques have not proved successful in delineating fault traces. Six profiles were acquired along several streets where the Wellington fault is not accurately known. We present and discuss two profiles demonstrating the applicability of GPR data to image the geometry and nature of active faults.