Importance of Geological Data in Probalistic Seismic Hazard Assessments: A Case Study from ETNE, Western Norway

In intraplate areas of low seismicity, any possible information about the existence of a large (ML>6.0) earthquake based on the local geology is quite valuable in estimating the true seismic hazard potential of the area of interest. Recent examples of destructive earthquakes from the seismically quiet areas such as India and Egypt, have demonstrated the often underestimated hazard potential of these areas. In conventional probabilistic hazard analyses, the seismic source zones are usually defined based on the instrumental catalogues which cover only the last 40–50 years, with a possible extension of a few hundreds of years from the historical data. The only source of information about the earlier events, is therefore dependent upon the detailed knowledge of the local geology of the area. In this study we demonstrate the importance of geological data in probabilistic seismic hazard assessments through an example from Etne in western Norway.