HR: 0800h
AN: T11A-1228    [Abstracts]
TI: Upper Mantle Seismic Anisotropy of the Ross Sea, Trans-Antarctic Mountains, and East Antarctica From SKS Splitting Analysis
AU: * Barklage, M E
EM: mitchb@levee.wustl.edu
AF: Washinton University, Dept. of Earth and Planetary Sciences, St. Louis, MO 63130
AU: Pozgay, S
AF: Washinton University, Dept. of Earth and Planetary Sciences, St. Louis, MO 63130
AU: Fisher-Lawrence, J
AF: Washinton University, Dept. of Earth and Planetary Sciences, St. Louis, MO 63130
AU: Shore, P
AF: Washinton University, Dept. of Earth and Planetary Sciences, St. Louis, MO 63130
AU: Wiens, D A
AF: Washinton University, Dept. of Earth and Planetary Sciences, St. Louis, MO 63130
AU: Nyblade, A
AF: Penn State University, Department of Geosciences, State College, PA 16804
AU: Anandakrishnan, S
AF: Penn State University, Department of Geosciences, State College, PA 16804
AU: Voigt, D
AF: Penn State University, Department of Geosciences, State College, PA 16804
AB: The Trans-Antarctic Mountains seismic experiment (TAMSEIS), a two year deployment of 43 broadband seismographs extending from Ross Island to the interior of East Antarctica, offers an excellent opportunity to study the anisotropic fabric of the Antarctic upper mantle, which is largely unconstrained. We analyze SKS and SKKS phases for shear wave splitting using the method of Silver and Chan (1991). To check the robustness of our results, we also utilize the cross-correlation method (Bowman and Ando, 1987) and visually inspect particle motions. The splitting functions are then stacked to obtain the best fit splitting parameters for each station. Results show that the Antarctic lithosphere beneath the Trans-Antarctic Mountains (TAM) and the adjacent East Antarctic craton are characterized by a uniform region of mantle anisotropy, with fast axes oriented at about N35E to N65E and splitting magnitudes of 0.5 - 1.0 seconds. This is consistent with azimuthal variations of Rayleigh wave phase velocities reported by Lawrence et al [2004]. The Rayleigh wave anisotropy is strongest at periods of about 40 seconds, suggesting the anisotropy is strongest in the uppermost mantle. This suggests that it represents upper mantle lattice preferred orientation that is remanent from past deformational episodes, rather than the current upper mantle flow pattern. The continuity of anisotropic directions between the TAM and the East Antarctic craton suggests the fabric is remnant from past deformational episodes, rather than a result of the current TAM uplift. The mapping of upper mantle anisotropic directions offers a possible method for delineating geologic terranes in ice-covered East Antarctica.
UR: http://epsc.wustl.edu/seismology/TAMSEIS/
DE: 7218 Lithosphere and upper mantle
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 7200 SEISMOLOGY
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting