SEISMIC HAZARD IN FENNOSCANDIA - A REGIONALIZED STUDY

A seismic hazard evaluation has been conducted for Fennoscandia, inclu ding Norway, Sweden, Finland, Denmark, areas of Russia, and adjacent s ea areas. Several subregions were considered. Data were taken from a F ennoscandian earthquake catalog comprising both macroseismic and instr umental observations. The analysis was based on a maximum likelihood a pproach using incomplete historical and complete instrumental data, di fferent detection thresholds, and assessment of earthquake magnitude u ncertainty. The output for the selected subregions consists of the pro babilities that a given magnitude will not be exceeded in a given inte rval of time and mean return periods for earthquakes of magnitudes exc eeding a given value M(L). The evaluated parameters are the maximum re gional magnitude, Gutenberg-Richler 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 appl ied method were observed: both the patterns of earthquake occurrence a nd the reporting of historical events tend to deviate from the model. Differences in output can be expected according to the decisions to de al with these discrepancies.