Date of Final Oral Examination (Defense)
Type of Culminating Activity
Master of Science in Geophysics
Lee M. Liberty, M.S.
Dylan Mikesell, Ph.D.
Mark Schmitz, Ph.D.
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This work is licensed under a Creative Commons Attribution-Share Alike 4.0 License.
Receiver functions derived from teleseismic earthquakes contain seismic amplitude and velocity information that relate to compositional changes within the Earth’s crust and upper mantle. The receiver function waveform is a combination of P-S converted waves that have reverberated within the lithosphere. Although the largest seismic velocity boundary is found at the base of the crust, I explore the use of lower amplitude receiver function arrivals that represent smaller velocity contrasts within the crust. In my thesis, I calculate and model receiver functions via a Metropolis algorithm approach to extract seismic velocity distributions in the lithosphere. I use the results to explore changing lithologies and heat signatures beneath the geologically complex southern Idaho region. In addition to a robust crustal thickness estimate for my study area, I show anomalously thick crust beneath the 14 Ma track of the Yellowstone hotspot compared to the surrounding regions, a thinner crust beneath the Oregon-Idaho graben and the Basin and Range province, and a distinct boundary between the Basin and Range and middle Rocky Mountains provinces. I highlight a high velocity zone between 6-14 km depth that is consistent with the presence of mid-crustal sills beneath the hot spot track, partial melt within the Yellowstone caldera, and relatively low velocities at seismogenic depths within the tectonic parabola of eastern Idaho. Anomalously slow velocities in the lower to mid-crust beneath the southern margin of the western Snake River Plain are coincident with high heat flow values and high total magnetic values, offering the possibility of mid-lower crustal partially melted dikes or sill complexes. I utilize legacy active source refraction data to compare with receiver function results to further constrain seismic velocities. Overall, I find that receiver function analyses using a Metropolis algorithm inversion approach to estimate seismic velocity distributions show results below 6 km that are consistent with other studies. This approach offers the possibility of complimenting large-scale refraction experiments with low-cost receiver function analysis by utilizing earthquake waveforms from both permanent and temporary seismic deployments to constrain mid to lower-crustal properties. I discuss the use of this method as a tool for geothermal exploration by constraining crustal lithologies and identifying the presence of partial melt.
Harper, Thomas Branson, "Crustal Composition Beneath Southern Idaho: Insights from Teleseismic Receiver Functions" (2018). Boise State University Theses and Dissertations. 1477.