CRUST AND UPPER MANTLE STRUCTURE OF WEST ANTARCTICA FROM A SPARSE SEISMIC ARRAY

• Main Author: Cho, Tongjun
• Other Authors: Sridhar Anandakrishnan, Charles J. Ammon, Joseph L. Rose, Bernhard R. Tittmann
• Format: Text
• Language: English
• Published: Penn State 2006
• Subjects: Acoustics; Antarctic; West Antarctic Ice Sheet; West Antarctica; Antarc*; Antarctica; Ice Sheet
• Online Access: http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-1209/index.html

The West Antarctic Rift System is poorly understood relative to the other major rift systems of the world because of the remoteness of Antarctica and because the West Antarctic Ice Sheet covers most of the rift. In this paper, the crust and upper mantle structures of the interior of the West Antarctic Rift System were investigated using broadband seismic data from five widely spaced stations installed on the West Antarctic Ice Sheet. The crust and upper mantle seismic wave velocity structures were modeled using receiver functions and the inter-station surface wave dispersion curves. A new surface waveform extraction technique involving ambient seismic noise field correlation was applied for refining the surface wave dispersion measurements. A method for removing the ice layer reverberation effects on the receiver functions was designed and applied to retrieve the receiver function for crust and mantle-only structure. The mantle anisotropy of the rift region was measured by shear wave splitting analysis. The crust and uppermost shear wave velocity structure modeled in this study show that the crust is relatively thin, which we hypothesize is due to extension of the West Antarctic Rift System. In support of this hypothesis, I show that the measured anisotropy indicates that the fast axis direction is rift orthogonal. I model an approx. 100km thick anisotropic layer in the upper mantle, which may represent preservation of fabric from the major Late Cretaceous extension between East and West Antarctica.