Seismic risk of circum-pacific earthquakes I. Strain energy release

Abstract

Commonly used earthquake “whole process” frequency - magnitude and strain energy - magnitude laws are merged to obtain an analytic expression for an upper bound magnitude to regional earthquake occurrenceM3, which is expressed primarily in terms of the annual maximum magnitudeM1 and the magnitude equivalent of the annual average total strain energy releaseM2. Values ofM3 are also estimated graphically from cumulative strain energy release diagrams. Both methods are illustrated by application to the high seismicity of the circum-Pacific belt, using Duda’s (1965) data and regionalisation. Values ofM3 obtained analytically, with their uncertainties, are in agreement with those obtained graphically. Empirical relations are then obtained betweenM1,M2, andM3, which could be of general assistance in regional seismic risk considerations if they are found to be of a universal nature. For instance.M3 andM2 differ by one magnitude unit in subregions of the circum-Pacific.