Distribution of historical earthquakes in southwestern Yukon and locations of major faults (dashed black lines).
Earthquakes and neotectonic activity (recent movement and deformation of the earth’s crust) in southwestern Yukon are associated with the subduction of the Yakutat micro-plate under the St. Elias Mountains. Small seismic events are common in southwestern Yukon, but large earthquakes may be about 50 years apart, judging from the recent historical record. Earthquakes occur on the Denali and Duke River fault systems, with larger ones along strands of the Fairweather fault near the coast of the Gulf of Alaska.
Seismicity can trigger a variety of natural hazards in southwestern Yukon, including: ground vibrations, large landslides and avalanches, liquefaction of saturated sediments, and surface rupture. Such phenomena could compromise the integrity of the Alaska Highway and potential Alaska Highway gas pipeline route, in addition to community infrastructure and local mine workings.
In 2002, a magnitude 7.9 earthquake occurred along the Denali Fault in Alaska approximately 350 km west of the Yukon/Alaska border. This earthquake ruptured the ground surface for 340 km, extending across both the Richardson Highway and the TransAlaska pipeline route in Alaska.
While the Yukon portion of the Denali Fault has accommodated up to 400 km of right-lateral strike-slip displacement in the past several million years, relatively little is known about the pre-historical history of this fault in the last few thousand years. New research conducted by USGS in 2008 suggested that large magnitude surface rupture earthquakes occurred along the Yukon portion of the Denali Fault around 1050 AD, 230 BC and 970 BC, which suggests an average recurrence interval of approximately 1000 years (Seitz et al., 2008).
Since 2008, YGS has been collaborating with a number of agencies to collect important baseline data that will improve our understanding of neotectonic activity in southwestern Yukon. This information will improve our ability to assess and manage related hazards.
Field activities currently include:
• lake sediment coring near Duke River to detect the frequency of large magnitude earthquakes that have occurred on the Denali Fault in the recent past (John Clague, SFU; Brian Menounos (UNBC); Panya Lipovsky & Jeff Bond, YGS)
• deploying and maintaining GPS and seismometer instrumentation to monitor present day earthquake activity (Mike Schmidt, Stephane Mazzotti & Charlie Roots, GSC)
• detailed geological mapping to better characterize the past history of Duke River fault (Rosie Cobbett, UBC; Steve Israel, YGS)
• Overview of neotectonics investigations in SW Yukon – Canadian Quaternary Association (CANQUA) 2009 talk [3.4 MB ]
• Earthquake Preparedness:
o GSC - Earthquakes Canada
o Yukon Emergency Measures Organization (EMO)
• Educational Resources:
o GSC – General Earthquake Information
o USGS – Earthquake Hazards Program
For more information about Earthquakes in the Yukon contact Panya Lipovsky.