New Zealand Journal of Geology and Geophysics abstracts
Late Quaternary movement on the Ohariu Fault, Tongue Point to MacKays Crossing, North Island, New Zealand
DAVID HERON
RUSS VAN DISSEN
Institute of Geological & Nuclear Sciences
P.O. Box 30 368
Lower Hutt, New Zealand
MASUMI SAWA
A-17, 327-7
Inooka, Wada
Tsuruoka City
Yamagata, Japan
Abstract The Ohariu Fault is one of the major active dextral
strike-slip faults in the Wellington region. It extends northeastward from
offshore at Tongue Point to Waikanae and beyond, but in the north the fault
trace becomes intermittent. Extrapolation of the trend of the Ohariu Fault
across Porirua Harbour suggests a 1.5 km right step.
South of Porirua Harbour the fault is characterised by lateral displacement of
drainage features of up to 450 m, a single-event lateral displacement of
4-5 m, an average horizontal slip rate of 1-2 mm/yr, and a recurrence
interval of 2000-5000 yr. The timing of the last event was between 150 and
1130 cal. BP. North of the harbour the fault is characterised by lateral
displacement of drainage features of up to 250 m, a single-event lateral
displacement of 2.9 m, a horizontal slip rate of 0.6-1.9 mm/yr, and a
recurrence interval of 1530-4830 yr. The timing of the last event was
between 1070 and 2310 cal. BP.
Although the possibility exists that Porirua Harbour is a pull-apart basin
marking separate rupture segments on the Ohariu Fault, the data suggest there
is a single rupture segment from Tongue Point to Waikanae. On this assumption,
the last movement on the fault occurred 1070-1130 yr ago. The average
horizontal surface displacement for the event was 3.7 m (based on seven
sites) and the estimated earthquake magnitude was Mw 7.1-7.5.
Keywords Ohariu Fault; Wellington; Porirua; Makara; Tongue
Point; Mackays Crossing; neotectonics; late Quaternary; active fault;
strike-slip; dextral; slip rates; NZMS 260 R26, R27
New Zealand Journal of Geology & Geophysics, 1998, Vol. 41:
419-439
0028-8306/98/4104-0419 $7.00/0 (c) The Royal Society of New Zealand
1998
PDF file of entire paper: medium quality (4947K); (scanned from paper original: notes about this process)
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