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.