| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | January 28, 2015 |
| Latest Amendment Date: | February 4, 2019 |
| Award Number: | 1454829 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Eva Zanzerkia
EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | February 1, 2015 |
| End Date: | January 31, 2022 (Estimated) |
| Total Intended Award Amount: | $527,248.00 |
| Total Awarded Amount to Date: | $527,248.00 |
| Funds Obligated to Date: |
FY 2017 = $117,306.00 FY 2018 = $124,575.00 FY 2019 = $57,611.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
5700 CASS AVE STE 4900 DETROIT MI US 48202-3692 (313)577-2424 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
0224 Old Main Detroit MI US 48201-1203 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): |
Geophysics, EDUCATION AND HUMAN RESOURCES |
| Primary Program Source: |
01001718DB NSF RESEARCH & RELATED ACTIVIT 01001819DB NSF RESEARCH & RELATED ACTIVIT 01001920DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
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.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
There were 3 major goals of this project:
1. Relate mineralogy and fabric strength to elastic anisotropy for lower crustal rock types.
2. Determine how structure affects observed anisotropy.
3. Increase the number and diversity of undergraduate students participating in research at an urban university.
Tangible outcomes were achieved under each of the 3 goals, but the most significant outcomes are under goals 1 and 3.
Intellectual Merit
The outcomes in intellectual merit fall under goals 1 and 2, and the most significant outcomes are under goal 1. We analyzed 110 samples, 55 from each of the two gneiss domes, Chester and Pelham domes. We were able to define a few clear relationships between mineralogy, fabric strength, and elastic anisotropy for the rocks of Chester and Pelham gneiss domes.
1. Minerals that develop strong crystallographic preferred orientations in response to strain, like mica and amphibole, show a positive correlation between the strength of the preferred orientation and the magnitude of the resulting elastic anisotropy. However, this correlation is not linear.
2. For amphibole, we were able to identify 3 different types of preferred orientation, and the resulting elastic anisotropy is highly dependent on the type of preferred orientation. The types of amphibole preferred orientation are likely related to the types of strain, although our study cannot confirm that relationship. This result suggests that for amphibole-rich rocks, like lower crustal amphibolites, elastic anisotropy may be used to distinguish the strain regime, i.e. between constriction, flattening, and pure shear.
3. For schists, the magnitude of elastic anisotropy is linearly correlated to the modal proportion of mica, and the specific type of mica does not significantly affect that relationship.
4. For amphibolites, the relationship between modal proportion amphibole and magnitude of anisotropy depends on the type of amphibole preferred orientation.
5. Trends in elastic tensor symmetry vs. mineralogy are slightly different between the two gneiss domes, in particular the effect of quartz is much stronger in Pelham dome than in Chester dome.
Broader Impacts
Perhaps the biggest outcome of this project is that 57 Wayne State undergraduate students gained field research experience through the Team Research course. More than half of these students were part of an underrepresented group in STEM: 30 were female, and 4 were underrepresented minority students. Of the 57 students, 23 continued on with research during their undergraduate career, and 13 have now gone on to pursue graduate education in a STEM field. Research projects that were initiated by students in Team Research have resulted in 3 Honor’s theses, and 8 student-led conference presentations. Furthermore, the Team Research course continues to be offered beyond the completion of this grant, and thus the impact will continue to grow.
4 Masters students were directly supported by this grant, resulting in 4 completed MS theses, and 6 conference presentations by those students. 3 of the 4 MS students have obtained jobs in their desired field.
Finally, developing and running the Team Research course has helped me to grow into my own as a teacher. Teaching students how to do research is very different than teaching a course like Mineralogy, but through working with students on research, I feel I have developed into a better teacher in all aspects of teaching.
Last Modified: 04/03/2023
Modified by: Sarah J Brownlee
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