Large earthquake recurrence in low seismicity regions: accounting for aperiodicity

Characterising earthquake hazard in low seismicity regions is challenging, due to both the inherent lack of data and an incomplete theoretical understanding of the controls on earthquake occurrence away from plate boundaries. In the plate boundary paradigm, elastic rebound theory predicts that cycles of strain accumulation and release will result in regular, or quasiperiodic, recurrence of large earthquakes on individual faults. Analysis of a global compilation of long-term earthquake records shows that this largely holds in plate boundary regions, but begins to break down in intraplate and other low seismicity regions, where more irregular, or aperiodic, earthquake recurrence is observed. In this talk the Otago region of southern New Zealand is used as a case study of a low seismicity region with evidence for aperiodic earthquake recurrence. New paleoearthquake and slip rate data are used to extend the record of faulting back more than 100 ka on two faults, the Hyde and Dunstan faults. These data allow the variability of earthquake rates on these faults to be characterised, with novel Bayesian methods developed to forecast the probability of future earthquakes. Finally, the talk discusses the potential for application of these methods in the Australian context.