Insights into deep structure and evolution of Alaska based on a decade of observations of shear wave splitting and mantle flow

Thesis (M.S.) University of Alaska Fairbanks, 2011This thesis covers shear wave splitting results from a decade of temporary networks deployed throughout Alaska. The analysis and interpretation of data from the MOOS (Multidiscipline Observations Of Subduction) and ARCTIC (Alaska Receiving Cross Transect for the Inner Core) PASSCAL (Program for Array Seismic Studies of the Continental Lithosphere) deployments, combined with the previously published BEAAR (Broadband Experiment Across the Alaska Range) results provide anisotropy and flow observations across the state. In south central Alaska, a region dominated by the subduction of the Pacific plate under the North American plate, fast directions are dominantly in the direction of convergence (NNW-SSE), or trench-normal. This is either due to entrained flow below the subducting portion of the Yakutat block, or anisotropy within the block itself. Farther north above the mantle wedge the shear wave splitting results are dominated by fast directions along the strike of the subducting slab (NE-SW), due to along strike flow within the mantle wedge. North of the mantle wedge, fast directions transition into a more NNE to SSW orientation which is the Brooks Range and North slope are in the direction of absolute plate motion.1. Introduction -- 1.1. Shear wave splitting and mantle anisotropy -- 1.2. Networks -- 1.2.1. Multidisciplinary observations of subduction -- 1.2.2. Alaska receiving cross-transect for the inner core -- 1.3. Tectonic setting -- 1.3.1. MOOS tectonic setting -- 1.3.2. 1964 Prince William Sound Earthquake -- 1.3.3. ARCTIC tectonic setting -- 2. Methods -- 3. Results -- 3.1. MOOS -- 3.2. ARCTIC -- 4. Discussion -- 4.1. North of the subducted Pacific Plate -- 4.2. South of the Subducted Plate -- 4.3. Global model and comparisons to other subduction zones -- 5. Conclusion: final model for splitting observations in Alaska -- References -- Appendices