New Zealand Journal of Geology and Geophysics abstracts
Short communication
Constraints on the timing of the three
most recent surface rupture events and recurrence interval for the
Ohariu Fault: trenching results from MacKays Crossing, Wellington, New
Zealand
Nicola Litchfield
Russell Van Dissen
David Heron
David Rhoades
GNS Science
P.O. Box 30 368
Lower Hutt, New Zealand
Abstract A trench across the Ohariu Fault at
MacKays Crossing revealed evidence and provided radiocarbon age
constraints for three surface-rupture events in the last 5300 cal. yr
BP. The two older events are dated for the first time at 5270–4410 and
4810–3260 cal. yr BP. The youngest event is correlated to the most
recent event, dated elsewhere along the Ohariu Fault, at 1050–1000 cal.
yr BP. Using statistical methods incorporating inter-event times, mean
slip rate, and single-event displacement, and their uncertainties, a
best estimate mean recurrence interval of 2200 yr is calculated
for the Ohariu Fault, with minimum and maximum 68% and 95% confidence
interval limits of 1300 and 3800 yr, and 800 and 7000 yr,
respectively. Following the procedures outlined in the Ministry for the
Environment Guidelines, these data place the Ohariu Fault in
Fault-avoidance Recurrence Interval Class II (>2000 to
≤3500 yr), with medium to low confidence of classification.
Keywords Ohariu Fault; MacKays
Crossing; Wellington; strike-slip fault; paleoseismology; recurrence
interval; alluvial fan; sea-cliff
G05024; Received 25 May 2005; accepted 26 September 2005; Online
publication date 28 February 2006
New Zealand Journal of Geology & Geophysics, 2006, Vol. 49:
57–61
0028–8306/06/4901–0057 © The Royal Society of New Zealand 2006
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