| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | January 8, 2013 |
| Latest Amendment Date: | March 24, 2014 |
| Award Number: | 1246903 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Eva Zanzerkia
EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | June 1, 2013 |
| End Date: | May 31, 2016 (Estimated) |
| Total Intended Award Amount: | $161,726.00 |
| Total Awarded Amount to Date: | $161,726.00 |
| Funds Obligated to Date: |
FY 2014 = $88,411.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
801 LEROY PL SOCORRO NM US 87801-4681 (575)835-5496 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
NM US 87801-4681 |
| 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 |
| Primary Program Source: |
01001415DB 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
Recent discoveries that demonstrate the wide spectrum of fault slip along subduction megathrust faults prompt important questions about the relationships between large earthquakes, small earthquakes, slow slip, and non-volcanic tremor. In many areas, the deep portion of the fault that lies at the transition between the fast and slower slip mechanisms is out of view, sitting offshore, away from nearby monitoring. However, an existing seismic and geodetic network along the Oaxacan segment of the Middle America subduction zone provides an excellent dataset for use to quantify earthquake occurrence and source parameters in an area that has experienced M > 7 earthquakes, tremor, and slow slip events.
This research will address several hypotheses related to the spatial and temporal relationships between slow slip, tremor, and large earthquakes. These include determining 1) if a sharp transition in seismicity characteristics exists along the megathrust as events approach the downdip seismicity limit and the area of episodic tremor and slip, 2) if slow slip events produce stress loading in adjacent regions that lead to increased seismicity rates and changes in source characteristics of small earthquakes, and 3) if large earthquakes are associated with temporal changes in earthquake occurrence and source characteristics in adjacent regions due to stress changes. We will employ several seismological techniques, including the construction of a uniform event catalog, focal mechanism determination, rupture duration and stress drop calculations, and investigation of seismicity rates along specific fault patches, to address these hypotheses.
The overall goals of the project revolve around a better understanding of the deep roots of the earthquake-producing region of the Mexican subduction zone, with applicability to other global subduction zones. Thus the results of the study will produce societal benefits related to earthquake hazards, particularly in providing information needed for improving temporal variations in probabilistic seismic hazard. The outcome of this project will include data products disseminated to a wide international community through meeting presentations, publications, and archival in the relevant data repositories. The project will train 4 US based graduate and undergraduate students as well as provide capacity-building seismological training for 2 Mexican students. Another outcome of the project will be 2 educational lessons that will be disseminated through online educational activity portals.
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 subduction megathrust, where the majority of large earthquakes occur around the world, is a fault that allows for motion of two tectonic surface plates. This fault not only produces the largest earthquakes and tsunami, but it also hosts a variety of fault slip processes, including slip so slow that it is observed only with geodetic instruments. Much of this very slow slip occurs at the deeper portions of the megathrust fault, and there are many questions remaining about what causes this slow slip, and how the slow slip might be connected to faster slip on the shallower megathrust. We studied over 380 small to moderate sized earthquakes along the Oaxaca segment of the Mexican subduction megathrust, largely in the region where the fast slip transitions into the slow slip, in order to study this transition. We find similarities between the deeper slower slip processes and other seismicity in the seismogenic zone, with the small earthquakes in areas adjacent to the slow slip events also having characteristics of slow slip or low stress ruptures. In addition, we find that the transition in earthquake characteristics is gradual, rather than sharp, which places some constraints on other studies underway to understand the required conditions for slow slip to occur on the megathrust fault. The project also provided training for 2 female students and international collaboration, with public dissemination of results in 4 international meeting presentations and a student M.S. thesis to date.
Our results will improve understanding of the regional tectonics and earthquake behavior along this portion of the Mexican subduction zone as well as the conditions required to produce slow slip events in Mexico, as well as around the world. Our results also provide new observations about how smaller magnitude earthquakes might be impacted by the conditions present in other slow slip zones, such as Cascadia, along the western North American margin.
Last Modified: 08/12/2016
Modified by: Susan L Bilek
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