HR: 0800h
AN: S41C-1032    [Abstracts]
TI: Upper mantle structure beneath the Transantarctic Mountains and East Antarctic Craton from P and S body wave tomography
AU: Watson, T
EM: tdw130@psu.edu
AF: Dept. of Geosciences, Penn State University, University Park, PA 16802 United States
AU: * Nyblade, A
EM: andy@geosc.psu.edu
AF: Dept. of Geosciences, Penn State University, University Park, PA 16802 United States
AU: Wiens, D
EM: doug@seismo.wustl.edu
AF: Dept. of Earth and Planetary Sciences, Washington University, St. Louis, MO 63130 United States
AU: Anandakrishnan, S
EM: sak@geosc.psu.edu
AF: Dept. of Geosciences, Penn State University, University Park, PA 16802 United States
AU: Benoit, M
EM: mbenoit@geosc.psu.edu
AF: Dept. of Geosciences, Penn State University, University Park, PA 16802 United States
AU: Shore, P
EM: partrick@seismo.wustl.edu
AF: Dept. of Earth and Planetary Sciences, Washington University, St. Louis, MO 63130 United States
AU: Voigt, D
EM: voigt@geosc.psu.edu
AF: Dept. of Geosciences, Penn State University, University Park, PA 16802 United States
AB: The Transantarctic Mountains (TAM) consists of gently tilted fault blocks resulting from vertical crustal movement during the Cenozoic. Paralleling much of the West Antarctic Rift System, the TAM has been considered to be a classic example of rift flank uplift by many, however origin of the uplift remains uncertain. Proposed uplift models include: flexural uplift augmented by a thermal load, isostatic uplift in response to crustal thickening, isostatic uplift in response to climate-triggered erosional unloading, and various combinations of these mechanisms. To investigate the origin of the TAM uplift, body-wave tomography was performed with broadband seismic data collected by the 2000-2003 Transantarctic Seismic Experiment (TAMSEIS). The multi-channel cross-correlation method of VanDecar and Crosson (1990) was utilized to determine relative P and S wave arrival times for teleseismic events. The corresponding travel-time residuals were inverted using the method of VanDecar (1991) to obtain images of velocity variations in the upper mantle. The P and S wave tomography models reveal a low velocity anomaly beneath Ross Island and adjacent portions of the TAM front in the upper 200-250 km of the mantle. The P model, exhibiting better resolution than the S model, indicates that the anomaly may be discontinuous beneath the TAM front to the north and south of Ross Island. Following the method of Karato (1993), the observed low velocity anomaly corresponds to a thermal perturbation of 200-300 K. Inland beneath East Antarctica both the P and S models reveal fast upper mantle velocities, as expected for cratonic lithosphere. The presence of a thermal anomaly beneath the TAM front corroborates models invoking flexural uplift augmented by a thermal load. However, the discontinuity of the anomaly beneath the mountain range to the north and south of Ross Island suggests that other uplift mechanisms may be important elsewhere along the TAM.
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 1212 Earth's interior: composition and state (7207, 7208, 8105, 8124)
DE: 1236 Rheology of the lithosphere and mantle (7218, 8160)
DE: 6982 Tomography and imaging (7270, 8180)
SC: Seismology [S]
MN: Fall Meeting 2005