HR: 13:55h
AN: NS23A-02    [Abstracts]
TI: Neotectonic Evolution of Normal Faults Within the Taupo Rift (New Zealand) Revealed Using High-Resolution 3D GPR Data
AU: * McClymont, A F
EM: amcclymont@aug.ig.erdw.ethz.ch
AF: Institute of Geophysics, ETH Zurich, Zurich, CH-8093, Switzerland
AU: Villamor, P
EM: p.villamor@gns.cri.nz
AF: GNS Science, PO Box 30368, Lower Hutt, 5040, New Zealand
AU: Green, A G
EM: alan@aug.ig.erdw.ethz.ch
AF: Institute of Geophysics, ETH Zurich, Zurich, CH-8093, Switzerland
AB: The complex shallow subsurface structures of active fault zones are generally difficult to characterize using traditional paleoseismic techniques like surface mapping and trenching. High-resolution 3D ground penetrating radar (GPR) is an excellent tool for imaging these structures, because GPR data can reveal both the complicated patterns of deformation across the fault zone and along-strike variations in fault morphology. We have acquired several 3D GPR data sets over a ~ 250 x 150 m region that crosses five steeply dipping normal faults within the active Taupo Rift of New Zealand. The kinematically linked faults have ruptured a late Quaternary stratigraphic sequence of fluvial sediments and volcanic tephras. A paleoseismic trench excavated at the same location has allowed us to correlate well-dated tephra units with at least three prominent reflections picked from the migrated and depth-corrected GPR volumes. By mapping offsets of these horizons across the faults, we have determined their tectonic evolution over the past ~ 20 ka. From the GPR data we have measured variations in displacement along the length of each fault and with time. We have also observed distributed strain between faults, including fault-related folding and progressive tilting of hanging-wall strata.
DE: 0900 EXPLORATION GEOPHYSICS
DE: 0935 Seismic methods (3025, 7294)
DE: 7221 Paleoseismology (8036)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 7250 Transform faults
SC: Near-Surface Geophysics [NS]
MN: 2007 Fall Meeting