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Abstract:
Seismic hazard assessment has advanced beyond relying solely on magnitude recurrence rates to incorporating additional parameters, such as faults and deformation rates. In the stable craton of Canada, active faults have been difficult to identify as there is only one earthquake with a known surface rupture (northern Quebec, 1989). Additional sources of information, such as GNSS and INSAR, have thus far been of limited value for hazard assessment in this region because of poor spatial coverage and the relatively modest sizes of recent earthquakes. Nevertheless, the region comprises several active seismic zones with well recorded earthquakes and large earthquakes have occurred historically. Building on an initial study of the Western Quebec Seismic Zone, statistical analyses of focal mechanisms focusing on modal values (e.g. Salvado-Gálvez et al. 2020) in all seismically active regions of southeastern Canada and the eastern Canadian Arctic are applied to determine probable fault planes. In the Canadian craton, this method has been successful in determining strike direction and dip angles but the results for dip direction have been largely equivocal. The results, however, have been useful for developing weighting schemes for incorporating dip directions into the hazard assessment. Additionally, relocations of active aftershock sequences in some seismic zones provide information about fault orientations. Although the impetus of this study is to provide input to future Canadian seismic hazard models, the results will also provide input to other research topics, such as associating earthquakes with actual faults.
