Quaternary Geology – An Essential Clue to Evaluating Seismicity

Abstract

The geologic record, particularly that of the late Quaternary period, is a far more valuable tool in estimating seismicity and associated seismic hazard than has generally been recognized. This is simply because, by looking into the recent geologic past, the geologist is able to overcome many of the statistical inadequacies of the relatively short instrumental and historic records. These shortcomings are best illustrated in those parts of the world with the longest historic records of earthquakes—2000 years for Japan and the Middle East and 3000 years for China—where surprising variations in both the rates of recurrence and places of recurrence are evident. These long records show that earthquakes are by no means uniform in space and time, at least over intervals of only 1000 or 2000 years.