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TitleSeismicity, geodynamics and seismic hazard in Yukon-western Northwest Territories
AuthorLeonard, L; Hyndman, R D; Cassidy, J F; Allen, T; Rogers, G C; Kao, H; Adams, J
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Abstracts Volume vol. 39, 2016 p. 51-52
LinksDownload entire publication / téléchargement de la publication au complet
Year2016
Alt SeriesEarth Sciences Sector, Contribution Series 20160028
PublisherGeological Association of Canada
Meeting"Margins Through Time" Geological Association of Canada - Mineralogical Association of Canada Joint Annual Meeting; Whitehorse, YT; CA; June 1-3, 2016
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceYukon; Northwest Territories
AreaSt-Elias Mountains; Mackenzie Mountains; Richardson Mountains
Subjectstectonics; faults; earthquakes; continental margins; crustal studies; earthquake studies; tectonic models; seismicity; faults, thrust; epicentres; faulting; Eskimo Lakes Fault zone
ProgramWestern Canada Geohazards Project, Public Safety Geoscience
AbstractThere is substantial earthquake occurrence and hazard in Yukon and western Northwest Territories that is not always appreciated. We describe the distribution of past earthquakes and hazard estimates based on the earthquake data file, geophysical and geological constraints and geodynamic models. There is exceptional seismicity in SW Yukon, adjacent Alaska and BC where the Yakutat terrane is colliding with the continental margin in the Gulf of Alaska, pushing up the spectacular St. Elias Mountains including Mt. Logan, Canada¿s highest mountain. The region has had numerous recorded magnitude 7 to 8 earthquakes in adjacent Alaska. Less well known is the strong seismicity in the Mackenzie Mountains, Richardson Mountains, and the Beaufort Sea regions, with a number of magnitude 6 to 7 recorded earthquakes. The earthquake record and high-precision GPS data support a tectonic model of the Yakutat terrane collision driving the northern Cordillera Yukon block to the north-northeast. The collision drives transpression in SW Yukon, thrust faulting in the Mackenzie Mountains, and dextral strike-slip faulting in the Richardson Mountains region that may extend northward to the continental margin through the Eskimo Lakes Fault zone. The Richardson dextral motion coupled with sinistral motion in the Canning displacement zone in eastern Alaska implies an intervening northward-moving crustal block and active convergence at the Beaufort Sea continental margin. Although there have been no historical large events, the Mackenzie Delta thrust front may be capable of infrequent but large thrust earthquakes with associated tsunamis. The northerly motion also may be responsible for the concentration of seismicity in the Beaufort Sea. There is steady improvement but still limited seismograph station coverage in northwestern Canada which limits the epicentre accuracies, correlations with mapped faults, and calculation of other earthquake parameters. Only earthquakes above about M3 are consistently located, and there is limited depth resolution and rupture mechanism determination. There have been significant recent advances in modelling the ground shaking hazard in the area, from better earthquake data, GPS data, and tectonic models. There are also better models that estimate the attenuation of strong ground shaking with distance, but the hazard characterizations are still only very regional. Future seismic hazard models for the region would benefit from an improved seismotectonic model of the region based on neotectonic evidence of active faulting and enhanced seismic and GPS observations.
Summary(Plain Language Summary, not published)
There is a substantial earthquake hazard in the Yukon and western Northwest Territories that is not always appreciated. We describe the distribution of past earthquakes and hazard estimates based on the earthquake data file, geophysical and geological constraints and geodynamic models. There have been significant advances in modelling the ground shaking hazard in the area, from better earthquake data, GPS data, and tectonic models. We describe improvements to seismic hazard models for the region using an improved seismotectonic model based on neotectonic evidence of active faulting and enhanced seismic and GPS observations.
GEOSCAN ID298720