A seismotectonic study of the Southeastern Alaska Region |
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| Authors: | Diane I Doser Hugo Rodriguez |
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| Institution: | 1. Department of Geosciences, University of Arkansas, 216 Ozark Hall, Fayetteville, AR 72701, United States;2. Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Building 130, 10100 Burnet Rd, Austin, TX 78758, United States;3. Kansas Geological Survey 1930 Constant Ave., Lawrence, KS 66047, United States;4. Department of Geology, University of Kansas, 1475 Jayhawk Blvd. Rm 120, Lawrence, KS 66045, United States;5. Department of Chemistry and Biochemistry, University of Arkansas, 119 Chemistry Building, Fayetteville, AR 72701, United States;6. Department of Geology and Geophysics, University of Alaska, Fairbanks, Reichardt, Rm 308, 900 Yukon Dr. P.O. Box 755780, Fairbanks, AK 99775, United States;7. Perot Museum of Nature and Science, 2201N. Field Street, Dallas, TX 75201, United States |
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| Abstract: | We compare relocations of recent (1973–2005) and historic (1919–1972) earthquakes to geologic and geophysical (gravity, aeromagnetic, and uplift) information to determine the relationship of seismicity to crustal deformation in southeastern Alaska. Our results suggest that along strike changes in the structure of the Pacific plate may control the location of the ends of rupture zones for large earthquakes along the offshore Queen Charlotte fault system in the southern portion of the study area. There is a marked increase in background seismicity in the northern portion of the study area where the Fairweather fault begins to bend toward the northwest and crustal uplift due to glacial unloading exceeds 20 mm/year. Focal mechanisms indicate that thrust and reverse mechanisms predominate in the region of maximum uplift, as might be expected by the decrease in ice sheet thickness. The diffuse nature of seismicity between the Fairweather and Denali faults in the northern study area suggests a complex interaction between plate/microplate interactions and glacial unloading, making it difficult to determine the optimal fault orientation for failure in moderate magnitude (5.5 to 6.5) earthquakes within this region. |
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