HR: 0800h
AN: T41C-1218    [Abstracts]
TI: New constraints on the Pleistocene slip rate of the Hope Fault, South Island, New Zealand.
AU: * Hall, L S
EM: lisa.hall@rms.com
AF: Risk Management Solutions, 7015 Gateway Blvd, Newark, CA 94560 United States
AU: Lamb, S
EM: simon.lamb@earth.ox.ac.uk
AF: Oxford University, Dept of Earth Sciences Parks Road, Oxford, OX1 3PR United Kingdom
AB: The Marlborough Fault Zone (MFZ) is a series of 4 major strike-slip faults which lie along the Australian-Pacific plate boundary in the northern part of the South Island, New Zealand. The MFZ accommodates almost all of the relative plate motion in this region and the most southerly structure, the Hope Fault, is considered to be the most active. Despite its regional significance, the Pleistocene slip rate of the Hope Fault remains poorly constrained and current geological estimates range between 18 and 35 mm/yr for its central segment. More robust slip rate measurements would therefore be important for seismic hazard analysis. At Sawyers Creek a flight of river terraces have been clearly offset by the Hope Fault. These have been used to calculate some of the existing published slip rates, however the complexity of the offset geomorphic features and the dating methods used limit the accuracy of these results. This study revisits the Sawyers Creek area, employing contemporary surveying and dating techniques to resolve these issues. Kinematic GPS height measurements are combined with interpretations of aerial photographs and field observations to produce a 2 m resolution digital elevation model of the offset features, and the detailed nature of this allows a reinterpretation of the offset distances. Optically stimulated luminescence dating of river silts from the terrace tread provides more accurate age constraints than the weathering rind dating technique used previously. The calculated slip rate of 18-20 mm/yr lies at the lower end of the range of published estimates, in line with the relative plate motion and geological slip rate estimates on the adjacent faults.
DE: 9355 Pacific Ocean
DE: 9604 Cenozoic
DE: 7223 Seismic hazard assessment and prediction
DE: 8010 Fractures and faults
DE: 8110 Continental tectonics--general (0905)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting