<title>3D ground penetrating radar applied to paleoseismology: examples from the Wellington Fault, New Zealand</title>

Abstract

The main goal of paleoseismology is to estimate future seismic hazard through an improved characterization of past fault behavior in seismically active environments. Paleoseismological investigations provide critical knowledge about ancient earthquakes that have occurred along active faults. Such knowledge may be used to refine estimates of local and regional seismic hazard. Earthquake-related features (e.g. faults, folds and fissure fill) observed in trenches and outcrops generally exhibit complex three-dimensional (3D) geometries. Ground penetrating radar (GPR) data allow information extracted from these conventional paleoseismological observations to be extrapolated and complemented. We have conducted detailed 2D and 3D GPR surveys at various locations along the Wellington Fault in the Hutt Valley of New Zealand. Fault-related structures are seen clearly in the GPR data as offsets or abrupt terminations of laterally continuous reflections. In cross-sections and time- slices extracted from the 3D GPR data sets, sudden changes of reflection pattern determine the principal fault plane. After applying a novel topographic migration scheme to the GPR data, individual lithologic units may be mapped. Our results correlate well with observations at nearby outcrops. They show that 3D GPR surveys are capable of supplying clear subsurface images in typical paleoseismological trenching environments. GPR images may be used to guide trenching strategies aimed at features of special interest to paleoseismology.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.