New Zealand Journal of Geology and Geophysics abstracts
Paleoseismology of the Waverley Fault Zone and implications for earthquake
hazard in South Taranaki, New Zealand
TRACEY TOWNSEND
Institute of Geological & Nuclear Sciences
PO Box 30 368
Lower Hutt, New Zealand*
*Present address: Schlumberger Geco-Prakla, P.O. Box 7496, Cloisters Square,
Perth WA 6850, Australia.
Abstract The Waverley Fault Zone, c. 40 km
northwest of Wanganui, New Zealand, has clearly defined surface fault scarps
trending southwest-northeast for a distance of c. 8 km, from Lake
Oturi in the south through to the Brunswick Terrace strandline northeast of
Waverley. Paleoseismic studies involving trenching were carried out to
determine the timing of past earthquakes, the amount of surface displacement
associated with them, and an estimation of associated earthquake magnitudes.
The Waverley Fault Zone has been the site of several large, surface-rupturing
events in the past. Trench excavations across the fault zone revealed that the
zone consists of normal faults dipping 50-80deg.SW, with a minimum of two
displacements having occurred since deposition of the Kawakawa Tephra
22 500 yr ago. Single-event fault displacements were measured to be at
least 1-2 m vertically. From these values the estimated earthquake
magnitudes associated with past earthquake events are calculated, using the
Wells & Coppersmith fault regression formula, to range from M 6.6 to
6.7. Calculations using the formula Mo = u ù L w
show significantly lower magnitudes, having a maximum value of M
6.5. An average value of M 6.3 was obtained and accepted by this
study.
Keywords Waverley Fault Zone; paleoseismic studies;
earthquake hazard; normal faulting; Kawakawa Tephra; Taupo Volcanic Zone;
Ngarino Terrace; Rapanui Terrace; Brunswick Terrace
New Zealand Journal of Geology & Geophysics, 1998, Vol. 41:
467-474
0028-8306/98/4104-0467 $7.00/0 (c) The Royal Society of New Zealand
1998
PDF file of entire paper: medium quality (1527K); (scanned from paper original: notes about this process)
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