HR: 16:30h
AN: S14C-03    [Abstracts]
TI: Statistical Assessment of Earthquake Recurrence for the W-HV Segment of the Wellington Fault, New Zealand
AU: * Langridge, R M
EM: r.langridge@gns.cri.nz
AF: GNS Science, P.O. Box 30-368, Lower Hutt, 5040, New Zealand
AU: Van Dissen, R J
EM: r.vandissen@gns.cri.nz
AF: GNS Science, P.O. Box 30-368, Lower Hutt, 5040, New Zealand
AU: Rhoades, D A
EM: d.rhoades@gns.cri.nz
AF: GNS Science, P.O. Box 30-368, Lower Hutt, 5040, New Zealand
AU: Villamor, P
EM: p.villamor@gns.cri.nz
AF: GNS Science, P.O. Box 30-368, Lower Hutt, 5040, New Zealand
AU: Wilson, K
EM: k.wilson@gns.cri.nz
AF: GNS Science, P.O. Box 30-368, Lower Hutt, 5040, New Zealand
AU: Litchfield, N
EM: n.litchfield@gns.cri.nz
AF: GNS Science, P.O. Box 30-368, Lower Hutt, 5040, New Zealand
AU: Stirling, M
EM: m.stirling@gns.cri.nz
AF: GNS Science, P.O. Box 30-368, Lower Hutt, 5040, New Zealand
AU: Clark, D
EM: dan.clark@ga.gov.au
AU: Lyman, A
EM: aaron.lyman@gmail.com
AU: Barnett, E
EM: eli@ess.washington.edu
AU: Carne, R
EM: carnerach@student.vuw.ac.nz
AB: New paleoseismic results from a data-rich trench on the Wellington-Hutt Valley (W-HV) segment of the Wellington Fault have allowed for a more robust statistical approach into earthquake recurrence on that fault. The paleoseismic data is used to generate Monte Carlo simulations of the event age and recurrence interval distributions. Based on a combination of stratigraphic (peats buried by colluvium/scree) and structural (faulting) evidence we recognise up to 4 dateable, co-seismic events in the Te Kopahou-1 trench, at the south coast of Wellington. We have developed 6 different earthquake event age models that draw increasingly on trench interpretations, data from previous trenches, and/or less certain data in order to extend the length of the paleoseismic record. In addition, for 4 of these examples we have run simulations in parallel with a Slip Rate-SED model of recurrence interval for the fault, using a lognormal distribution of a c. 140 kyr slip rate (6-7.6 mm/yr) in combination with a single event displacement (SED) of 4.2 +/- 1.3 m (i.e. SED with CoV of 0.3). We present here two variations of the results from 20,000 random number results; in which both of the distributions include the effects of the Slip Rate-SED model. The first, which includes the last 3 dated paleo- earthquake events with some interpretative weighting gives a mean, median, and 95% lower and upper bounds of 641, 605, 332, and 1107 yr, respectively for earthquake recurrence. The second model includes the last 4 dated paleo-earthquake events (3 inter-event times) with increased interpretive weighting. This model yields recurrence times with parameters of 625, 591, 352, and 1074 yr, respectively. These same 2 models run using the paleoearthquake data alone yield mean intervals of c. 903 and 742 yr based on 3 and 4 events, respectively. We recognise that the recurrence interval distributions are lognormal in form (as is the Slip Rate model). The Slip Rate distribution, the CoV on SED, and the paleoearthquake record each have significant uncertainties that drive the recurrence interval results. The beauty of our technique is that all of these uncertainties are taken into account. Further work will be undertaken to improve these models to output the most robust recurrence model for New Zealand's highest seismic risk fault segment.
DE: 7221 Paleoseismology (8036)
DE: 7250 Transform faults
DE: 8002 Continental neotectonics (8107)
SC: Seismology [S]
MN: 2007 Fall Meeting