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TitreSeismic hazard in western Canada from global positioning system vs. earthquake catalogue data
AuteurMazzotti, S; Leonard, L J; Cassidy, J C; Rogers, G; Halchuk, S
SourceSSA 2010, abstracts of the Annual Meeting; Seismological Research Letters vol. 81, no. 2, 2010 p. 364-365,
LiensOnline - En ligne
Séries alt.Secteur des sciences de la Terre, Contribution externe 20100153
Réunion2010 Annual Seismological Society of America Meeting; Portland; US; avril 21-23, 2010
Documentpublication en série
Mediapapier; en ligne; numérique
ProvinceAlberta; Colombie-Britannique
Sujetssecousses séismiques; catalogues des tremblements de terre; études séismiques; géophysique
ProgrammeÉvaluations ciblées des dangers dans l'Ouest du Canada, Géoscience pour la sécurité publique
Diffusé2010 03 01
Résumé(disponible en anglais seulement)
Probabilistic seismic hazard analyses are principally based on frequency-magnitude statistics of historical and instrumental earthquake catalogues. This method assumes that return periods of large damaging earthquakes (100s - 1000s yr) can be extrapolated from 50-100 yr statistics of small and medium earthquakes. The method has obvious limitations when applied to areas of low-level seismicity where the earthquake statistics may be poorly constrained. In this study, we test an alternative approach to assess seismic hazard in Western Canada. We use horizontal velocities at ~250 Global Positioning System (GPS) sites in BC and Alberta to calculate strain rates and earthquake statistics within seismic source zones. GPS-based strain rates are converted to seismic moment, earthquake frequency-magnitude statistics, and seismic hazard using a logic-tree method. The GPS-based earthquake statistics and seismic hazard are then compared to those derived from the earthquake catalogue. In one zone (Puget Sound), the GPS seismic hazard estimates are in good agreement with those from earthquake statistics. In nearly all other zones (e.g., most of BC and Alberta), the GPS seismic hazard estimates are significantly larger than those from the earthquake catalogue by one or two orders of magnitude. This discrepancy could indicate that the earthquake catalogue significantly under predicts long-term seismic hazard in areas of low-level seismicity. Alternatively, significant aseismic deformation may occur over long time-scales, which would imply that the GPS strain rates over predict the true seismic hazard. We discuss the nature and limitations of both methods in light of our results for Western Canada, with the goal of defining a methodology to incorporate GPS strain rate data into probabilistic seismic hazard assessments.