Historical earthquakes: a case study for Adelaide 1954 earthquake

Abstract

The accuracy of a seismic risk assessment is related to the time span of the data base. The longer the seismicity of an area is observed, the better the ability to predict future activity. Historical records of earthquakes stretch back more than four times the period of instrumentally recorded earthquakes, so the value of historical earthquakes and isoseismal maps is of great importance for calibration of ground motion models because the building type is taken into account during assigning of the intensity values and such maps reflect the local geology and soil characteristics. Of interest to the insurers are also interrelated aspects of risk calculation such as the expected earthquake occurrences, maximum magnitudes and intensities, and anticipated damage. We have used a well-documented case of the Adelaide 1954 earthquake to address these aspects and tried to compare the MM intensities with the damage ratios for the purposes of loss calculation. Our estimates expressed in percentage of the effective loss of the replacement value of insured dwellings in Adelaide are comparable with the results of the recent studies by the insurance industry.