| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | April 13, 2011 |
| Latest Amendment Date: | October 6, 2015 |
| Award Number: | 1062238 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Margaret Benoit
mbenoit@nsf.gov (703)292-7233 EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | July 1, 2011 |
| End Date: | January 31, 2017 (Estimated) |
| Total Intended Award Amount: | $391,185.00 |
| Total Awarded Amount to Date: | $391,185.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
1500 SW JEFFERSON AVE CORVALLIS OR US 97331-8655 (541)737-4933 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
1500 SW JEFFERSON AVE CORVALLIS OR US 97331-8655 |
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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): | Marine Geology and Geophysics |
| 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): | 47.050 |
ABSTRACT
The sizes and locations of earthquakes recorded by eight hydrophones moored in the Equatorial Atlantic Ocean provide an unparalleled view of the seismicity of the poorly understood slow-spreading Mid-Atlantic Ridge in this region. The data also allow testing of the idea that earthquakes can be predicted at ocean transform faults, and they provide insight into how triple junctions (where three tectonic plates meet) work. The Equatorial Atlantic seafloor has not been studied extensively but is interesting for many reasons. First, the Mid-Atlantic Ridge axis is offset on some of the longest transform faults in the oceans. As an example, the Romanche transform is greater than 900 km long. In places, the transform offsets are so large that the total length of the transform faults is longer than the total length of the ridge axis. These fracture zones are extremely rugged, are important conduits for bottom water moving between the North and South Atlantic Ocean, and probably act as physical barriers blocking the transport of hydrothermal vent fauna along the ridge axis. The Equatorial Atlantic transforms are ideal for testing the short-term predictability of earthquakes at ocean transform faults and the results may help in understanding earthquakes on continental faults. A second interesting aspect of the region is that it contains the triple junction where the North America, South America, and Africa tectonic plates meet. The exact location of the triple junction is still a matter of debate, and this study will help to define its location. Third, the location of the plate boundary between the North America and South America plates is not known even though there is motion between the plates. The earthquakes recorded by the hydrophones provide important new information about the motion of these two plates, and how and where that motion is taking place. The hydrophone array also records a variety of natural and man-made noises and will facilitate a wide-range of studies beyond the scope of the proposed work. Examples include the use of ambient sound measurements to study various climate research topics, including estimating wave heights, rainfall intensity and wind speed during hurricanes. In addition, recorded whale vocalizations allow the distribution and migration of these animals to be tracked throughout the Equatorial Atlantic Ocean.
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.
The goal of this project is investigate whether large mainshock earthquakes on faults in the Atlantic ocean exhibit foreshock activity that warns of the impending forshock. We believe the Atlantic faults may exhibit these warning foreshocks, because faults in the Pacific exhibit them as well. Thus these foreshocks may be used to forecast, even predict, earthquakes on these ocean faults.
Our project is different from typical seismic studies because we use hydrophones to detect the earthquake signals. Hydrophones are underwater microphones and can record very small earthquake signals, much smaller magnitude earthquakes than can be detected by seismometers on land. Thus we record many more small magnitude earthquakes which provides us with a much more complete picture of behavior of these ocean faults.
Faults in the ocean tend to exhibit more regular, predicitable, earthquake behavior because both sides of the fault are made of the same type of ocean rock. This rock is made up of basalt, peridotite, and gabbro, and when thee rocks are exposed to seawater, they will metamorphose into a very slick mineral called seprentine. Serpentine allows the fault to slide easily, and thus the fault exhibits a very regular pattern of buidling up stress, then releasing the stress through earthquakes. Also the faults are super saturated by the sewater, which has the effect of lubricating the faults and allowing them to slide very easily.
We have a drafted a manuscript that shows, preliminarily, that there are foreshock precursors to mainshock on at the northern Mid-Atlantic ridge segments and the Blanco Transform fault segments in the NE Pacific ocean. Our ultimate goal will be to see if these methods to forecast earthquakes in the ocean can be used to forecast earthquakes on land.
Last Modified: 03/06/2017
Modified by: Robert P Dziak
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