| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | July 2, 2019 |
| Latest Amendment Date: | July 2, 2019 |
| Award Number: | 1835947 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Eva Zanzerkia
EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | July 15, 2019 |
| End Date: | June 30, 2023 (Estimated) |
| Total Intended Award Amount: | $294,088.00 |
| Total Awarded Amount to Date: | $294,088.00 |
| Funds Obligated to Date: |
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| Recipient Sponsored Research Office: |
4202 E FOWLER AVE TAMPA FL US 33620-5800 (813)974-2897 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
4202 E. Fowler Ave. NES 201 Tampa FL US 33620-9998 |
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Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | XC-Crosscutting Activities Pro |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
The great earthquakes and tsunamis of 2004 (Sumatra) and 2011 (Japan) were wake-up calls that our forecasting skill for these catastrophic events remains weak. Measurement of the slow motions of the Earth's surface near active faults could help to forecast the location and the size of future earthquakes. This project tests the concept by operating a network of a high precision GPS receivers in Costa Rica. This area is an active subduction zone that experiences frequent large earthquakes. The GPS units will measure ground motion for a 3-year period with a precision of a few millimeters per day. This will continue a long history of geodetic observations here that now span both the late and early stages of the earthquake cycle. The data from this project will improve understanding of the earthquake process, and could lead to improvements in our ability to forecast these potentially deadly events. UNAVCO, the NSF-funded consortium for geodesy, will provide critical maintenance support for the network. The broader impacts of the study include impacts on earthquake hazards and also help to train the next generation of scientists through support for a PhD graduate student.
The existence of earthquake clusters in subduction interfaces suggests that not all accumulated strain is necessarily released in an earthquake, and can be stored over a seismic cycle for release in a subsequent, larger than average event. With the discovery of slow slip events (SSEs: earthquake-like phenomenon within the interseismic phase that release energy slowly) it is now clear that determination of a full strain accumulation budget, and improved understanding of frictional conditions on the plate interface, also require study and understanding of these interseismic strain release mechanisms. Data from the 2012 Costa Rica earthquake suggests that a pre-event SSE changed Mohr Coulomb failure stress by a trivial amount, although other failure mechanisms are possible. SSEs are also important indicators of frictional conditions. Shallow SSEs are an important subset, and while generally difficult to observe, can be clearly seen in northern Costa Rica due to proximity to the trench. They may be critical for understanding tsunami potential in this difficult-to-observe region. More generally, SSEs may outline the region of subsequent seismic rupture, this pattern has now been documented in the active margins off Costa Rica, Ecuador and parts of Japan. This project deploys geodetic infrastructure to better observe and understand these slow slip events in the Nicoya Peninsula.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
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.
Subduction zones, where one geologic plate is pushed beneath another, generate some of Earth’s biggest natural hazards, including destructive earthquakes and tsunamis. Measuring the associated strain accumulation is one way to understand and perhaps forecast these catastrophic events, and is possible with modern geodetic techniques that exploit the precise positioning capabilities of GPS and GNSS receivers. Our project has operated a high precision GNSS network in Central America for many years, and we use these data to study the strain accumulation/release processes associated with subduction. Briefly, during the multi-decade long strain accumulation phase of the earthquake cycle, the upper plate (in our case, the Caribbean plate, including its leading edge in Central America) shortens by measurable amounts, up to half an inch per year. While this may seem small, over many decades it can result in plate shortening of several meters (ten feet or more). This ‘elastic strain’ must ultimately be released, either as an earthquake, or more gradually, in a series of slow slip events. In our case, both have been observed, but the ratio of seismic (earthquake) release versus slow slip release can make a big difference in the destructive potential of the earthquake. We can’t yet predict earthquakes (in some ways the ‘holy grail’ of earthquake research) but being able to reliably forecast the intensity of future earthquakes is a useful first step, enabling improved building codes so that our built infrastructure can withstand future shaking.
Our Central American research project resulted in three graduate students receiving their PhDs: Surui Xie (PhD 2020) currently a faculty member at the University of Houston; Nicolas Voss (PhD 2021) currently working in Silicon Valley’s high-tech industry, and Mitchell Hastings (PhD 2023), currently working in the insurance industry on natural hazard analysis.
Last Modified: 10/20/2023
Modified by: Timothy Dixon
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