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TitreSeismic hazard in western Canada from GPS strain rates versus earthquake catalog
AuteurMazzotti, S; Leonard, L J; Cassidy, J F; Rogers, G C; Halchuk, S
SourceJournal of Geophysical Research vol. 116, B12310, 2011 p. 1-17,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20110036
Documentpublication en série
Mediapapier; en ligne; numérique
ProvinceColombie-Britannique; Alberta; Région extracotière de l'ouest
SNRC82; 83; 92; 93; 102; 103
Lat/Long OENS-134.0000 -110.0000 56.0000 46.0000
Sujetsrisque sismique; déformation; secousses séismiques; analyses; magnitudes des séismes; catalogues des tremblements de terre; risque de tremblement de terre; études séismiques; zones sismiques; analyses statistiques; méthodes statistiques; distributions de probabilité; failles; zones de subduction; géophysique; géomathématique
ProgrammeTargeted Hazard Assessments in Western Canada, Géoscience pour la sécurité publique
Résumé(disponible en anglais seulement)
Probabilistic seismic hazard analyses (PSHA) are commonly based on frequency - magnitude statistics from 50 - 100 year-long earthquake catalogs, assuming that these statistics are representative of the longer-term frequency of large earthquakes. We test an alternative PSHA approach in continental western Canada, including adjacent areas of northwestern U.S.A., using regional strain rates derived from 179 Global Positioning System (GPS) horizontal velocities. GPS strain rates are converted to earthquake statistics, seismic moment rates, and ground shaking probabilities in seismic source zones using a logic-tree method for uncertainty propagation. GPS-based moment rates and shaking estimates agree well with those derived from earthquake catalogs in only two zones (Puget Sound and mid-Vancouver Island). In most other zones, GPS-based moment rates are 6 - 150 times larger than those derived from earthquake catalogs, and shaking estimates are 2 -5 times larger. This discrepancy may represent an under-sampling of long-term moment rates and shaking probabilities by earthquake catalogs in some zones; however a systematic under-sampling is unlikely over our entire study area. Although not demonstrated with a high confidence level, long-term regional aseismic deformation may account for a significant part of the GPS / catalog discrepancy and, in some areas, represent as much as 80 - 90% of the total deformation budget. In order to integrate GPS strain rates in PSHA models, seismic vs. aseismic partitioning of long-term deformation needs to be quantified and understood in terms of the underlying physical and mechanical processes.