Abstract - The Taupo Rift in the central North Island of New Zealand is a region of active
extension of up to 15 mm/yr in the back-arc of the Hikurangi subduction system. Mapping
and trenching has defined a network of active normal faults. Because the paleoseismic
and historical earthquake catalogs are short and inhomogeneous, a deterministic computer
model of seismicity has been constructed to better understand the earthquake history.
The model consists of 26 primary normal fault segments (corresponding to mapped faults
with vertical displacement rates of 0.1–1.6 mm/yr) and 4700 randomly distributed small
normal faults in a 40 x 25 km area. All of the model faults interact elastically.
Parameters of the model are adjusted to reproduce the geologically observed displacement
rates, a regional b value of ca 1.0, and average slip/event of ca 1 m. The result is a long
catalog of 500,000 events, magnitude 3.82 to 6.62, which simulates a time period of
2 Myr. Characteristic slip events on each segment are mostly well defined and their
recurrence times can usually be described by a three parameter Weibull distribution. The
coefficient of variation (CV) for recurrence intervals ranges from 0.12 to 1.22 with an
average of 0.66; these reduce by about half if fault interactions are turned off. The time
series of characteristic earthquakes shows clear evidence of triggered slip up to about
3 years after large magnitude events, followed by relative seismic quiescence. On all
segments the moment release rate is relatively stable over time periods of more than about
five recurrence intervals (2–20 kyr) but can vary on time scales less than that.
Journal of Geophysical Research 114, B12306, 2009.