Abstract: Earthquake source characteristics provide a valuable constraint on fault behaviour, crustal stress, and regional plate tectonics. In southwestern Yukon, a region of complex active tectonics, studies of earthquake sources have historically been limited by sparse seismic network coverage. In this work, we leverage recent improvements in station coverage to estimate focal mechanisms for small and moderate-magnitude (M ≥ 2.0) earthquakes from P-wave first-motion polarity data. We invert these data using a probabilistic method that rigorously quantifies mechanism uncertainties. We present preliminary solutions for 363 events, which improve the spatial coverage of the focal mechanism catalogue for this region. We observe contrasting P-axis orientations for events on either side of the Fairweather fault. For events within southwestern Yukon, the distribution of faulting mechanism types and P-axis orientations are relatively consistent. Our focal mechanism solutions support the existence of an unmapped fault south of the Duke River fault. Finally, our results provide a valuable input for subsequent detailed analysis of crustal stress throughout the region.

Authors: Gosselin, J.M, Biegel, K, Hamidbeygi, M. and Dettmer, J.

NTS Mapsheet(s): 105B, 105C, 105D, 105E, 105F, 105G, 105L, 105M, 115A, 115B, 115C, 115F, 115G, 115H, 115I, 115J, 115K, 115N, 115O, 115P

Citation: Gosselin, J.M, Biegel, K, Hamidbeygi, M. and Dettmer, J., 2023. Improvements in the regional earthquake focal mechanism catalogue for southwestern Yukon. In: Yukon Exploration and Geology 2022, K.E. MacFarlane (ed.), Yukon Geological Survey, p. 63–76 plus digital appendices.

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