T008-03
Upper Mantle Seismic Anisotropy of Antarctica from Shear Wave Splitting Analysis

Tuesday, 8 December 2020: 04:08
Virtual
Erica Margaret Lucas, Pennsylvania State University Main Campus, University Park, PA, United States, Natalie J Accardo, Pennsylvania State University, Department of Geosciences, University Park, PA, United States, Andrew Nyblade, Pennsylvania State University Main Campus, Department of Geosciences, University Park, PA, United States, Andrew Jason Lloyd, Columbia University, Lamont-Doherty Earth Observatory, Palisades, NY, United States, Richard C Aster, Colorado State University, Geosciences Department, Fort Collins, CO, United States, Douglas A Wiens, Washington University in St Louis, Department of Earth and Planetary Sciences, St. Louis, MO, United States, John Paul O'Donnell, University of Leeds, Leeds, LS2, United Kingdom, Graham William Stuart, University of Leeds, School of Earth and Environment, Leeds, United Kingdom, Terry J Wilson, Ohio State University, Columbus, OH, United States, Ian W D Dalziel, University of Texas at Austin, Institute for Geophysics, Austin, TX, United States, John Paul Winberry, Central Washington University, Department of Geological Sciences, Ellensburg, WA, United States and Audrey D Huerta, Central Washington University, Ellensburg, WA, United States
Recorded Presentation
Abstract:
Using seismic data collected between 2008 and 2018 by the Polar Earth Observing Network (POLENET/A-NET), UK Antarctic Network (UKANET), and Gamburtsev Antarctic Mountains Seismic Experiment (GAMSEIS), we constrain azimuthal anisotropy in the Antarctic upper mantle using shear wave splitting parameters obtained from teleseismic SKS, SKKS, and PKS phases. After employing the Teanby cluster-analysis algorithm to pick robust windows around individual seismic phases, we applied an eigenvalue technique to linearize the rotated and shifted shear wave particle motions and determine the best splitting parameters. Each splitting measurement was inspected and assigned a quality rating based on several factors, including signal-to-noise ratio, linearity of particle motion, and error contours. We stacked the best results from each station to determine average splitting direction and delay time. Delay times generally range from 0.3 s to 1.0 seconds across Antarctica. Throughout both East and West Antarctica, fast anisotropic directions are not consistent with the Antarctic absolute plate motion, indicating that the anisotropic fabric does not result from shear associated with the motion of the Antarctic plate over the mantle. Our results, along with previous studies, reveal a number of mantle regimes within both East and West Antarctica. In East Antarctica, fast splitting directions are predominantly oriented parallel to the axes of the Gamburtsev Subglacial Mountains and adjacent Vostok Subglacial Highlands. Within the West Antarctic Rift System (WARS), we find fast anisotropic directions oriented subparallel to the inferred WARS extension direction. Variable fast directions and delay times observed within Marie Byrd Land may be indicative of complex mantle fabric, possibly resulting from a mantle plume. Anisotropy throughout Queen Elizabeth Land and the Haag-Ellsworth Whitmore Mountains crustal block may be attributed to deformation associated with the Jurassic extension of the Weddell Sea Rift System.
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