| NSF Org: |
OPP Office of Polar Programs (OPP) |
| Recipient: |
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| Initial Amendment Date: | October 11, 2011 |
| Latest Amendment Date: | October 11, 2011 |
| Award Number: | 1139739 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Mark Kurz
OPP Office of Polar Programs (OPP) GEO Directorate for Geosciences |
| Start Date: | January 1, 2012 |
| End Date: | June 30, 2014 (Estimated) |
| Total Intended Award Amount: | $70,408.00 |
| Total Awarded Amount to Date: | $70,408.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
801 UNIVERSITY BLVD TUSCALOOSA AL US 35401-2029 (205)348-5152 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
201 7th Ave., 2031 Bevill Bldg. Tuscaloosa AL US 35487-0104 |
| 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): | ANT Earth Sciences |
| Primary Program Source: |
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| 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): | 47.078 |
ABSTRACT
Intellectual Merit:
Numerous candidate models for the geologic processes that have shaped the Antarctic continent have been proposed. To discriminate between them, detailed images of the upper mantle structure are required; however, the only existing continental-scale images of seismic structure beneath Antarctica lack sufficient resolution to delineate important, diagnostic features. Using newly available data from various Antarctic seismic networks, the PI will employ the adaptively parameterized tomography method to develop a high-resolution, continental-scale seismic velocity model for all of Antarctica. The proposed tomography method combines regional seismic travel-time datasets in the context of a global model to create a composite continental-scale model of upper mantle structure. The proposed method allows for imaging of finer structure in areas with better seismic ray coverage while simultaneously limiting the resolution of features in regions with less coverage. This research will help advance understanding of important global processes, such as craton formation, mountain building, continental rifting and associated magmatism. Additionally, the proposed research will have important impacts on other fields of Antarctic science. Constraints provided by tomographic results can be used to develop thermal models of the lithosphere needed to characterize the history and dynamics of ice sheets. Also, further constraints on lithospheric structure are required by climate-ice models, which are focused on understanding the cooling history of the Antarctic continent.
Broader impacts:
The PI is a new faculty member at the University of Alabama after having been funded as a National Science Foundation Postdoctoral Fellow in Polar Regions Research. The graduate student supported by this project is new to polar research. Through the UA-Tuscaloosa Magnet School partnership program, the PI will educate K-12 students about the Antarctic environment and associated career opportunities through various online and hands-on activities. University of Alabama dedicates a significant percentage of its enrollment space to underrepresented groups.
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.
Seismic tomography is a commonly employed technique used to image the Earth’s subsurface structure and to understand deep geologic processes. Most tomographic approaches divide the study area of interest into a series of equally-sized grid cells, and the velocity within those cells is adjusted to match the observed travel times of seismic waves. However, by forcing all the cells to have the same size, the model is equally parameterized between areas with many seismic rays passing through them (i.e. more data) and areas with fewer rays (i.e. less data), which can cause resolution issues in the final velocity model. In this project, we instead use an adaptively parameterized tomographic approach, where the cell sizes are determined by the seismic ray path coverage. Areas with increased ray coverage correspond to smaller cell sizes, where improved resolution can be obtained.
Our study area of interest is the continent of Antarctica. The subsurface structure of Antarctica is much less resolved than beneath other continents given an historic paucity of data, leading to a relative lack in understanding of its geologic history and ongoing processes. Presently available continental-scale models for Antarctica provide only broad interpretations of the subsurface structure. Therefore, we have generated the first continental-scale adaptively parameterized tomography model for Antarctica using data from many new seismic network. Our results highlight considerably more subsurface heterogeneity than previous continental-scale models and provide higher resolution imaging to deeper mantle depth.
Beneath East Antarctica, fast velocities are consistent with ancient (Archean- or Proterozoic-aged) continental lithosphere, but slower velocities beneath the Polar Subglacial Basin near South Pole may reflect a suture, where two sections of continental lithosphere were joined. A boundary between fast velocities in East Antarctica and slow velocities in West Antarctica is found about 100-150 km beneath the Transantarctic Mountains, which roughly divide Antarctica in half. Slow velocities beneath Ross Island may reflect rift-related processes. Further into West Antarctica beneath Marie Byrd Land, slow seismic velocities extend to great depths in the mantle (~800 km), and these are interpreted as the signature of a mantle plume. Our new model provides important new insights on the subsurface geologic processes shaping the Antarctic continent.
Last Modified: 07/11/2014
Modified by: Samantha E Hansen
