Seismic investigations of the northern Transantarctic Mountains

• Main Author: Graw, Jordan Hunter
• Other Authors: Hansen, Samantha E., Robinson, D. M., Stowell, Harold Hilton, Zhang, Bo, Wiens, Douglas Alvin
• Format: Thesis
• Language: English
• Published: University of Alabama Libraries 2017
• Subjects: Geophysics; Geology; Ross Sea; Transantarctic Mountains; Antarc*; Antarctica
• Online Access: http://ir.ua.edu/handle/123456789/3175

Electronic Thesis or Dissertation Stretching ~3500 km across Antarctica and reaching elevations of ~4500 m, the Transantarctic Mountains (TAMs) are the largest non-compressional mountain chain on Earth. The TAMs show no evidence of folding or reverse faulting as is typically seen in contractional mountain building, calling the origin of the mountain range into question. Using data from the recent Transantarctic Mountains Northern Network seismic deployment, this dissertation integrates Rayleigh wave surface wave tomography, downward continuation and wavefield decomposition, and seismic anisotropy studies to better characterize the structure beneath the northern TAMs and to assess uplift. Surface wave tomographic images indicate a previously unidentified low shear wave velocity anomaly beneath the northern TAMs, with faster seismic velocities behind the TAMs front. The low shear wave velocity anomaly is interpreted as reflect rift-related decompression melting associated with Cenozoic extension. Uplift for the TAMs is attributed to a thermal buoyancy force associated with this anomaly. When trying to assess crustal structure, ice coverage is typically troublesome as reverberations in the ice layer can complicate the P-wave response. Downward continuation and wavefield decomposition removes the effect of ice layers on the P-wave response, resulting in signal that can be directly modeled for Earth structure. Inversion solution models agree well with results from previous studies based on S-wave receiver functions and tomography, confirming relatively thin crust beneath the northern TAMs. Upper mantle structure can also be assessed with seismic anisotropy. I performed shear wave splitting analyses on PKS, SKS, and SKKS phases to obtain the splitting parameters (fast axis directions φ and delay times δt). Behind the TAMs front, the anisotropic signature is interpreted as relict fabric “frozen” into the lithosphere from tectonic processes in the geologic past. Near the Ross Sea coastline, the signature is ...