Name
Earthquake relocations and temporal variability of seismicity in southwest Yukon
Description
Due to its location at a plate boundary between the Pacific and North American plates and the Yakutat microplate, southwest Yukon is undergoing complex active deformation causing abundant seismicity. There are multiple large connected fault systems in southwest Yukon that represent different transpressional regimes including the Fairweather, Denali, and Duke River fault systems. In this study, we look at two major datasets to analyze the tectonic deformation in Yukon. First, we look at statistical catalogue analysis of historical seismicity in southwest Yukon, including estimation of magnitude of completeness, regional b-values, and aftershock analysis for the 2002 Denali Earthquake. We combine these general catalogue studies with an analysis of double-difference earthquake relocations for ~5500 earthquakes from 2010 to 2021. From our relocation results, we are able to provide depth constraints on regional seismicity and show that deformation is brittle in the upper 10 km of the crust. We interpret new faults connecting the Totschunda and Denali faults and map the Connector fault between the Totschunda-Duke River to the Fairweather fault systems. Our analyses of both the historical and modern catalogues demonstrates the fault systems within southwest Yukon are interconnected, and that stress within the systems can be distributed and accommodated on adjacent faults. Overall, we are able to characterize tectonic deformation and motion as occurring on rigid-block boundaries defined by major faulting systems, as opposed to diffuse deformation.