| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | May 12, 2010 |
| Latest Amendment Date: | December 20, 2013 |
| Award Number: | 0952166 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Gregory Anderson
greander@nsf.gov (703)292-4693 EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | July 1, 2010 |
| End Date: | June 30, 2016 (Estimated) |
| Total Intended Award Amount: | $285,504.00 |
| Total Awarded Amount to Date: | $285,504.00 |
| Funds Obligated to Date: |
FY 2011 = $126,761.00 FY 2012 = $68,619.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
1664 N VIRGINIA ST # 285 RENO NV US 89557-0001 (775)784-4040 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
1664 N VIRGINIA ST # 285 RENO NV US 89557-0001 |
| 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): | EARTHSCOPE-SCIENCE UTILIZATION |
| Primary Program Source: |
01001112DB NSF RESEARCH & RELATED ACTIVIT 01001213DB 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
Collaborative Research: Geodetic Constraints on the Kinematics of the Colorado Plateau and its Western and Southern Margin
The Colorado Plateau, southwestern United States, has played an important role in the geologic evolution of the Pacific-North America plate boundary zone. Unlike most other parts of the western U.S., the Colorado Plateau has remained largely intact during most of its geologic history. Indeed, the area shows little to none active earthquake faults. However, earthquakes do happen within the Colorado Plateau, and some very large ones have occurred in southern Arizona and northern Mexico.
This project uses precise GPS measurements to establish how the crust of the Colorado Plateau moves relative to stable North America. Interpretation of the horizontal velocities tells the investigators whether the area moves as a coherent block or is internally deforming. In case of the former little earthquake activity is expected, and in case of the latter the seismic hazard in the region may be higher than currently thought. The deformation implied by the GPS data and earthquake data is compared in order to assess whether the earthquake activity can be related to the deformation measured in this project or whether they are due to other processes, such as gravitational collapse.
To perform the measurements, 33 new GPS stations are installed in Arizona, southern Utah and southeastern Nevada. These stations complement and densify the long-running continuous GPS stations of NSF EarthScope's Plate Boundary Observatory. The additional stations are needed to create well-constrained models to describe the region's present-day tectonics. With a well-constrained model of the deformation can the origin of the motion and deformation of the Colorado Plateau be investigated. Some of the models that are considered include a rigid motion of the plateau causing opening of the Rio Grande Rift, crustal extension encroaching into the plateau due to evolving mantle processes, and the effect of Pacific plate motion on the deformation of the southern Basin and Range.
Many of the new GPS stations are installed in National Parks and Monuments, as well as in State Parks. The investigators provide educational material to inform the parks on the active tectonics of the region and the aim of the project. The goal of these outreach activities is to educate the parks' visitors that the geologic wonderland they are in is actively changing due to geologic processes. Measurements are made for four years and the project involves training of a graduate student. The outcome of this project may be used in a reassessment of the seismic hazard in the region?s urban centers.
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.
This project was aimed at monitoring the Colorado Plateau and southern Basin and Range in Arizona with high-precision GPS stations in order to determine how and how much the area moves laterally compared to stable North America. Data prior to this project was inconclusive whether the whole area is slowly extending in an east-west direction similar to the northern Basin and Range area, or whether the Colorado Plateau moves as a coherent crustal block away from North America. We installed 34 new GPS stations throughout Arizona, southern Utah, and southern Nevada. We operated the network for six years and analysed the data along with those from existing stations that were installed and operated as part of NSF EarthScope's Plate Boundary Observatory. Unfortunately, it has been difficult to answer the questions posed above, because a few months before the start of the project in 2010, a large earthquake occurred near the San Andreas Fault system, just south of the US-Mexico border. What became clear through our subsequent analysis is that the lateral motion of the crust in a large part of the study changed in speed and orientation after the earthquake compared with before. Consequently, the concept of long-term crustal motion was jeapordized and no conclusions can be drawn except to say that the deformation field in the study area must often be affected by the occurrence of large earthquakes in southern California. The process that is responsible for this is called visco-elastic deformation. This means that the sudden stress change in the Earth due to the earthquake gets transmitted into the lower crust and upper mantle, where the stresses relax slowly because of the viscous behavior of these layers. We know from the northern Basin and Range that this relaxation can take 100+ years. One important thing we set out to do is to infer what level of viscosity would explain the observed changes in motion at the surface. We found that the mantle has to be weaker (i.e., lower viscosity) than the lower crust to explain the observations. This explains why we see the effect of this earthquake so far away because deformation in the upper mantle has a much larger spatial reach than deformation in the lower crust. The most important conclusion from our project is that deformation in a large part of our study area is time-dependent, which probably also means that the associated seismic hazard is time-dependent.
This project has benefited from the fieldwork support of many graduate and undergraduate students. The project also supported a student for a summer internship through the RESESS program (Research Experiences in Solid Earth Sciences for Students)
Last Modified: 10/31/2016
Modified by: Cornelis Kreemer
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