Abstract
Regions of low seismicity present a particular challenge for probabilistic seismic hazard analysis when identifying suitable ground motion models (GMMs) and quantifying their epistemic uncertainty. The 2020 European Seismic Hazard Model adopts a scaled backbone approach to characterise this uncertainty for shallow seismicity in Europe, incorporating region-to-region source and attenuation variability based on European strong motion data. This approach, however, may not be suited to stable cratonic region of northeastern Europe (encompassing Finland, Sweden and the Baltic countries), where exploration of various global geophysical datasets reveals that its crustal properties are distinctly different from the rest of Europe, and are instead more closely represented by those of the Central and Eastern United States. Building upon the suite of models developed by the recent NGA East project, we construct a new scaled backbone ground motion model and calibrate its corresponding epistemic uncertainties. The resulting logic tree is shown to provide comparable hazard outcomes to the epistemic uncertainty modelling strategy adopted for the Eastern United States, despite the different approaches taken. Comparison with previous GMM selections for northeastern Europe, however, highlights key differences in short period accelerations resulting from new assumptions regarding the characteristics of the reference rock and its influence on site amplification.
Highlights
Seismic hazard and risk analysis on a regional scale requires the characterisation of ground motion in regions of high seismic activity, and tectonically stable regions with little seismicity
In representing the complete epistemic uncertainty in the ground motion logic tree for stable cratonic environments, it is still necessary to return to the original hypothesis that strong motions in this region of Europe display fundamentally different source, path and site characteristics to those found within the European Strong Motion flatfile (ESM) database
The characterisation of ground motion and its epistemic uncertainty for application to stable cratonic region of Europe requires special consideration in comparison to the broader approach adopted for shallow seismicity followed elsewhere
Summary
Seismic hazard and risk analysis on a regional scale requires the characterisation of ground motion in regions of high seismic activity, and tectonically stable regions with little seismicity. Despite greater uncertainty in the source, path and site properties, selection of only a small number of models (especially those adopting similar seismological assumptions) will inevitably result in a smaller spread in the epistemic uncertainty This phenomenon was exemplified in the 2013 European Seismic Hazard Model (ESHM13) (Woessner et al 2015), wherein only two ground motion models (Toro 2002; Campbell 2003) were selected for application to the cratonic region of northeastern Europe (the Baltic Sea and surrounding counties), in stark contrast to the more active regions of Europe for which the logic tree contained four to six GMMs that were selected on the basis of their fit to observed data (Delavaud et al 2012). Though the primary target of this investigation is the prediction of ground motion for seismic hazard assessment in northeastern Europe and its uncertainties, we believe that the approach illustrated here be considered as a possible strategy for application in similar tectonic environments elsewhere on the globe
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