Research Papers
Frequency of occurrence of catastrophic earthquakes
Euan Smith & Warwick Smith - IGNS
The probabilities of occurrence in a five year period of a specified small number of catastrophic earthquakes, i.e. ones that are expected to cause losses of B$0.5 to B$1.0, have been calculated by generating synthetic seismicity catalogues based on the historical catalogue and a range of reasonable assumptions about earthquake occurrence. The principal assumption is that the rate of occurrence of M>7 earthquakes in the main seismic region of New Zealand is 20 per 100 years.
The models developed enable the solution of different problems specified by the same types of parameters, so that e.g., the specified number of events, the specified time interval and the specified excess may be varied, whereupon a corresponding solution may by readily calculated.
For models which made no special provision for clustering of earthquakes in time, the probability of sustaining three or more catastrophes in a five year period ranges from less than four in 10,000 for B$1 loss events to 35 in 10,000 for B$0.5 loss events.
For a model where clustering is as bad as the most active five years of the historical period, viz, during 1929-1934, the probability increases to about 15 in 10,000 for B$1 events and 174 in 10,000 (1.7%) for B$0.5 events.