Historical incidence of Modified Mercalli intensity in New Zealand and comparisons with hazard models
Abstract
The historical incidence of Modified Mercalli intensity produced by earthquakes of magnitude Mw ≥ 5.25 and depth ≤ 100 km has been determined for 47 locations in New Zealand for the period 1840-1997 inclusive. Maps for the return periods of intensities MM4 - MM7 were prepared. The effects of the highly attenuating Taupo Volcanic Zone (TVZ) were shown to be important for hazard both in the zone and in areas to the north-west of it. The rate of occurrence of the higher intensities was found to be about 2.5 times greater in the first century of the study period than in the last 50 years. The historical seismic hazard rates for intensities MM5 and MM6 averaged across the country were found to be approximately half those of the now obsolete Smith & Berryman seismic hazard model, and 70% of those of the more recent Stirling et al model.