3D ground penetrating radar applied to paleoseismology: examples from the Wellington Fault New Zealand

摘要

Abstract: The main goal of paleoseismology is to estimate futureseismic hazard through an improved characterization ofpast fault behavior in seismically active environments.Paleoseismological investigations provide criticalknowledge about ancient earthquakes that have occurredalong active faults. Such knowledge may be used torefine estimates of local and regional seismic hazard.Earthquake-related features (e.g. faults, folds andfissure fill) observed in trenches and outcropsgenerally exhibit complex three-dimensional (3D)geometries. Ground penetrating radar (GPR) data allowinformation extracted from these conventionalpaleoseismological observations to be extrapolated andcomplemented. We have conducted detailed 2D and 3D GPRsurveys at various locations along the Wellington Faultin the Hutt Valley of New Zealand. Fault-relatedstructures are seen clearly in the GPR data as offsetsor abrupt terminations of laterally continuousreflections. In cross-sections and time- slicesextracted from the 3D GPR data sets, sudden changes ofreflection pattern determine the principal fault plane.After applying a novel topographic migration scheme tothe GPR data, individual lithologic units may bemapped. Our results correlate well with observations atnearby outcrops. They show that 3D GPR surveys arecapable of supplying clear subsurface images in typicalpaleoseismological trenching environments. GPR imagesmay be used to guide trenching strategies aimed atfeatures of special interest to paleoseismology. !9