| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | November 27, 2015 |
| Latest Amendment Date: | November 27, 2015 |
| Award Number: | 1600890 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Eva Zanzerkia
EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | December 1, 2015 |
| End Date: | November 30, 2017 (Estimated) |
| Total Intended Award Amount: | $99,990.00 |
| Total Awarded Amount to Date: | $99,990.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
1523 UNION RD RM 207 GAINESVILLE FL US 32611-1941 (352)392-3516 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
Gainesville FL US 32611-2120 |
| 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): |
International Research Collab, DEEP EARTH PROCESSES SECTION |
| 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 PIs proposed to deploy 20 broadband seismic stations for one year in the rupture zone of the Mw 8.3 Illapel, Chile earthquake. The instruments will enable locating and characterizing thousands of aftershocks from the large earthquake. This data can be used to better understand the Nazca-South America plate interface as well as the processes behind the megathrust rupture and postseismic activity. The ability to capture the high seismicity rate immediately after the earthquake will enable both a finer picture of the subduction structure, as well improve our understanding of seismic hazard in the region.
The vigorous aftershock series now occurring in the wake of the 2015 Illapel, Chile Earthquake provides a rare opportunity to study syuduction zone segmentation, as delineated by adjacent megathrust ruptures. While the aftershock seismicity rate is high, researchers can take advantage to illuminate the Nazca and South American interplate interface, looking for evidence of differences in slip regime as discernible from aftershock locations and characteristics such as focal mechanisms, slip speed and spectral and attenuation characteristics. The deployment will produce a high quality, open access data set that will capture time-limited phenomena.
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 Mw=8.3 Illapel, Chile, earthquake ruptured a segment of the Nazca-South America subduction zone directly to the north of the 2010 Maule Mw 8.8 earthquake. Shortly thereafter the PIs and Chilean collaborators installed 20 broadband seismic stations to record aftershocks for one year. The spatial and temporal proximity of the Maule and Illapel events provided an unprecedented opportunity to examine possible structural controls on rupture segmentation: results from P wave and attenuation tomographies carried out using the Maule data set, in conjunction with studies of the rupture processes of that event, reveal that the presence of a large, dense, ultramafic body situated deep in the Chilean forearc crust, likely acted as a rupture asperity. This body, the Cobquecura anomaly, is possibly a product of Triassic rifting of the Chilean margin. Triassic rifting affected other areas of the margin, and outcrops of rocks related to the rifting occur within the Illapel rupture zone, as defined by aftershocks. The new data collected as the main activity of thisproject will allow us to assess the hypothesis that dense ultramafic Triassic rifting structures, distributed throughout the Chilean forearc crust in the study area, acted as asperities and may play a part in rupture segmentation and slip distribution along the subduction interface.Among targets related to evolution of the Andean margin, we note that, unlike the Maule event, the Illapel earthquake triggered a significant number of earthquake in the southern Andean ‘flat slab’ region. Preliminary analyses of hypocenters of these events lead us to believe that the slab structure in this area may be more complicated than previously thought. Possible interpretations of these new data include a slab tear and perhaps a vertical doubling of the subducted Nazca lithosphere instead of a smoothly contorted slab morphology. Alternatively, the hypocenters may be indicative of ‘normal’ subduction of the Nazca slab beneath an area of delaminating South American lithosphere. Validation of the hypothesis that particular geologic structures are clearly associated with rupture segmentation, as we suspect may be the case for Triassic ultramafic bodies present in the Chilean forearc crust, will allow Chilean civil defense authorities will use this knowledge to refine seismic and tsunami hazard assessments. Such a result could also spur searches for similar structures in the overriding lithosphere of other subduction zones.
Last Modified: 07/11/2018
Modified by: Raymond M Russo
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