CAREER: Seismic Anisotropy, Symmetry and Structure - Translating Laboratory Measurements into Seismic Interpretations

Wayne State University, Detroit MI

Investigators

Abstract

The research objective of this project is to determine the factors controlling the magnitude and symmetry of lower crustal seismic anisotropy - directional dependence of seismic velocity - from cm- to km-scale. The ability to interpret seismic data based on the elastic properties of rocks is critical to understanding the composition and structure of the middle and lower continental crust, yet there remains a distinct gap in our understanding of the causes of seismic anisotropy in the crust vs. anisotropy in the mantle. These results will have a significant impact on our ability to interpret seismic observations of crustal anisotropy, and will lay the groundwork for improving seismic methods for measuring crustal anisotropy. The knowledge gained by this work has the potential to transform the way we think about crustal seismic anisotropy, and the resulting improved understanding of the middle and lower crust will ultimately lead to improved models of seismic hazard. The proposed work also includes development of an innovative, tiered peer-mentoring approach to undergraduate research that can be applied in any discipline, and will have significant broader impacts related to undergraduate education and research, as well as participation of underrepresented minority students in a STEM discipline at an urban university. The PI proposes to improve our understanding of the causes of seismic anisotropy in the crust by developing a predictive framework linking mineralogy, texture, and structure to seismic anisotropy using middle and lower crustal rocks exposed at gneiss domes in the northeastern United States. The approach combines laboratory measurements of intrinsic, or cm-scale, elastic properties using electron backscatter diffraction (EBSD) with field measurements and mapping of 0.5-10 km-scale structures in two gneiss domes. Field and laboratory measurements will be used to model and predict the observed seismic anisotropy - magnitude and symmetry -resulting from middle and lower crustal structures at wide-ranging length-scales. Coordinated with the scientific goals of this project, she proposes to develop and implement an innovative teaching approach, Team Research, to increase the number and diversity of undergraduate students participating in research at an urban university. Team Research will be built around a tiered peer-mentoring system, where equal proportions of introductory, intermediate, and advanced undergraduate students work in teams, during a semester long course, to design and implement a field research project relevant to the scientific objectives of this study. Team Research will provide quality field and research experience in a STEM field to 60 undergraduate students from an urban university (12 per year). The anticipated increase in undergraduate students participating in research, in particular related to this project, is likely to contribute to increased diversity of undergraduate geology majors that are qualified and interested in pursuing a graduate degree.