Why Do Large Earthquakes Appear to be Rarely “Overdue” for Aotearoa New Zealand Faults?

Abstract

Understanding temporal patterns of surface‐rupturing earthquakes is critical for seismic hazard assessment. We examine these patterns by collating elapsed time and recurrence interval data from paleoseismic and historical records in Aotearoa New Zealand. We find that the elapsed time since the last earthquake is less than the mean recurrence interval for the majority (∼70%–80%) of the >50 faults sampled. Calculated mean recurrence intervals using slip per event and slip rate for these faults do not indicate systematic bias of the paleoseismic recurrence‐interval dataset due to missing earthquakes. Stochastic modeling of elapsed times indicates that the rarity of elapsed times greater than the mean recurrence interval is consistent with positively skewed Weibull and lognormal recurrence‐interval models. Regardless of the precise explanation for the short elapsed times, the majority of faults sampled are unlikely to be chronically late in their seismic cycles.