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TitleMoment magnitude - local magnitude calibration for earthquakes in western Canada
 
AuthorRistau, J; Rogers, G C; Cassidy, J FORCID logo
SourceBulletin of the Seismological Society of America vol. 95, no. 5, 2005 p. 1994-2000, https://doi.org/10.1785/0120050028 Open Access logo Open Access
Year2005
Alt SeriesEarth Sciences Sector, Contribution Series 2005528
PublisherSeismological Society of America (SSA)
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceAlberta; British Columbia; Northwest Territories; Yukon
NTS72E; 72L; 72M; 73D; 73E; 73L; 73M; 74D; 74E; 74L; 74M; 75D; 75E; 75L; 75M; 76D; 76E; 76L; 76M; 77B; 77C; 77F; 77G; 78B; 78C; 78F; 82; 83; 84; 85; 86; 87; 88A; 88B; 88C; 88D; 88E; 88F; 92; 93; 94; 95; 96; 97; 98A; 98B; 98C; 98D; 98E; 98F; 102; 103; 104; 105; 106; 107; 114; 115; 116; 117
Areawestern Canada; Washington State; Puget Sound; Canada; United States of America
Lat/Long WENS-145.0000 -110.0000 75.0000 45.0000
Subjectsgeophysics; tectonics; seismology; earthquake magnitudes; earthquakes; earthquake studies; moment measures; seismic data; plate tectonics; subduction zones; continental crust; downgoing slab; seismic risk; tectonic setting; plate motions; Canadian Cordillera
Illustrationssketch maps; focal mechanisms; plots
ProgramNatural Hazards and Emergency Response
ProgramNational Earthquake Hazards Program (NEHP)
AbstractLocal magnitude (ML) is the primary magnitude scale calculated for western Canada by the Geological Survey of Canada (gsc). Moment magnitude (Mw), derived from moment tensor analysis, provides a more robust estimate of the magnitude of earthquakes but is more demanding to calculate. Moment tensor analysis of regional seismic data for earthquakes with magnitudes larger than 3.5 in western Canada is now possible owing to the installation of more than 40 three-component broadband stations in western Canada, the Pacific Northwest of the United States, and southeast Alaska. More than 100 regional moment tensor solutions have been calculated in the Canadian Cordillera and Vancouver Island/Puget Sound region for 1996-2004 at the gsc. These solutions, along with 45 prior solutions, allow the calibration of Mw-ML throughout much of western Canada. Continental crust events in the Canadian Cordillera and Vancouver Island/Puget Sound region are found to have Mw = ML for earthquakes with ML ? 3.6. In contrast, earthquakes located within the subducting slab in the Vancouver Island/Puget Sound region, where there are complex source-receiver travel paths, have Mw systematically larger than ML by nearly 0.6 magnitude units. The calibrations of Mw with ML are an important result that will allow the western Canadian earthquake database to be used more effectively for tectonic studies and seismic hazard analysis.
GEOSCAN ID221505

 
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