Receiver function studies in the southwestern United States and correlation between stratigraphy and Poisson's ratio, southwestern Washington State
This dissertation consists of two separate lines of research. The first uses the receiver function technique to estimate crustal thickness and Poisson's ratio for three receiver stations in the southwestern United States. One station is located in El Paso because relatively few geophysical experiments have been conducted in the southern Rio Grande rift. Two stations are located on the Colorado Plateau, in an attempt to resolve an ongoing dispute concerning the crustal thickness of this province. The results of the receiver functions studies are used as additional constraints for gravity models along two regional profiles coincident with the much shorter profiles of the Pacific to Arizona Crustal Experiment (PACE) that was led by the U.S. Geological Survey on the Colorado Plateau. Because the profiles extend into adjacent provinces, these models are balanced for isostatic equilibrium and are consistent with elevations predicted by buoyancy calculations. The results are most consistent with a thick (≈50 km) crust for the Colorado Plateau and do not support the presence of large lateral thickness variations within the plateau. The second line of research presented also derives Poisson's ratio, in this case from seismic refraction data. The results are used to interpret a structural cross-section in southwest Washington State and to shed light on a feature of low resistivity (1–5 Ωm) located in the High Cascades (the Southern Washington Cascades Conductor or SWCC). This feature is delineated by the interpretation of magnetotelluric and seismic reflection profiles and has been interpreted to be largely composed of Lower Eocene marine sedimentary rocks. Both lines of research estimate Poisson's ratio using dissimilar techniques, but have produced results consistent with one another. Poisson's ratio for quartz-rich rocks (such as sandstones and granites) generally lies between 0.23 and 0.26, as exemplified by the upper crust of the Rio Grande rift, and by sedimentary rocks in southwest Washington. In comparison quartz-poor rocks generally exhibit Poisson's ratios between 0.28 and 0.32, typical of the lower crust and the many basaltic formations that comprise the upper crust in southwest Washington. (Abstract shortened by UMI.)
Kilbride, Fiona Elizabeth Anne, "Receiver function studies in the southwestern United States and correlation between stratigraphy and Poisson's ratio, southwestern Washington State" (2000). ETD Collection for University of Texas, El Paso. AAI9980093.