Seismic hazard in Fennoscandia: A regionalized study

A seismic hazard evaluation has been conducted for Fennoscandia, including Norway, Sweden, Finland, Denmark, areas of Russia, and adjacent sea areas. Several subregions were considered. Data were taken from a Fennoscandian earthquake catalog comprising both macroseismic and instrumental observations. The analysis was based on a maximum likelihood approach using incomplete historical and complete instrumental data, different detection thresholds, and assessment of earthquake magnitude uncertainty. The output for the selected subregions consists of the probabilities that a given magnitude will not be exceeded in a given interval of time and mean return periods for earthquakes of magnitudes exceeding a given value ML. The evaluated parameters are the maximum regional magnitude, Gutenberg-Richter b-value, and annual activity rate, all with standard errors. The obtained parameters correspond well to the characteristic seismicity features of inspected regions. However, discrepancies between the data used and the data model behind the applied method were observed: both the patterns of earthquake occurrence and the reporting of historical events tend to deviate from the model. Differences in output can be expected according to the decisions to deal with these discrepancies. © 1993.