| NSF Org: |
OCE Division Of Ocean Sciences |
| Recipient: |
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| Initial Amendment Date: | July 20, 2022 |
| Latest Amendment Date: | July 20, 2022 |
| Award Number: | 2217468 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Scott M. White
scwhite@nsf.gov (703)292-8369 OCE Division Of Ocean Sciences GEO Directorate for Geosciences |
| Start Date: | August 1, 2022 |
| End Date: | July 31, 2024 (Estimated) |
| Total Intended Award Amount: | $100,459.00 |
| Total Awarded Amount to Date: | $100,459.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
4333 BROOKLYN AVE NE SEATTLE WA US 98195-1016 (206)543-4043 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
4333 Brooklyn Ave NE Seattle WA US 98195-0001 |
| 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): | Marine Geology and Geophysics |
| Primary Program Source: |
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| Program Reference Code(s): | |
| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
The Cascadia Subduction Zone in the Pacific Northwest is a region of great national interest and growing public awareness because of its high earthquake and tsunami hazard. The Cascadia margin has low levels of recorded seismicity, which reduces what is known of the properties of the earthquake zone. This project aims to identify variations in the structure and properties of the Cascadia margin to better understand the earthquake and tsunami risk to the Pacific Northwest. This project will work with other groups to build a new 3-dimensional picture for the margin. The project will support for four graduate students, two postdoctoral researchers, and three early-career scientists.
From June 1 to July 11, 2021, a regional-scale multi-channel seismic study of the Cascadia Subduction Zone was collected using the state-of-the-art long-offset capabilities of the R/V Marcus G. Langseth as part of the CAscadia Seismic Imaging Experiment 2021 (CASIE21). During the expedition, 5,347 km of high quality 12-15 km streamer data were acquired in a 50-75 km spaced grid of seismic lines spanning the margin from the northern Gorda plate at 42°N to the end of subduction offshore Vancouver Island and from ~50 km seaward of the deformation front to near the coastline. This new survey represents the first regional-scale study conducted at Cascadia, spanning most of the subduction zone and filling important gaps in data coverage. This project utilizes the CASIE21 dataset in order to study nearly the whole Cascadia margin and will yield unique insights into three core questions: (1) What is the geometry of the plate interface along the margin, where is significant sediment subduction occurring, and how do plate interface properties including reflectivity and roughness vary along the margin and down dip? How do plate interface properties relate to incoming plate and upper plate structure and megathrust rupture segmentation? (2) How do the structural style and evolution of the upper plate vary along strike and how are they related to megathrust strength, backstops, and fluid migration? (3) How does the lithostratigraphic architecture of the sediment section, and structure, deformation and hydration potential of the shallow-most oceanic crust of the incoming plate associated with bend faulting, distribution of seamounts and propagator shear zones vary along the margin and how do these properties contribute to wedge evolution and megathrust rupture segmentation? This study will result in construction of a new regional-scale structural interpretation of the offshore Cascadia region from seismic images as a primary product along with select studies making use of reflectivity, velocity models, and strain analysis.
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.
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.
The Cascadia Subduction Zone in the Pacific Northwest is a region of great national interest and growing public awareness because of its high earthquake and tsunami hazard. The Cascadia margin has low levels of recorded seismicity, which reduces what is known of the properties of the earthquake zone. This collaborative project aims to identify variations in the structure and properties of the Cascadia margin to better understand the earthquake and tsunami risk to the Pacific Northwest. This project has contributed to a broader grand-challenge effort to build a new 3-dimensional understanding of the faulting, fault history, and tsunamigenic potential of the Cascadia subduction zone offshore. picture for the margin.
In 2021, a study of the Cascadia Subduction Zone was collected, by an multi-institutional team, using reflected seismic waves to make images of the Cascadia Fault and surrounding geology of the plate boundary fault zone along a series of transects from the deep ocean to the continental shelf off the coasts of Oreogn, Washington, and Vancouver Island. The University of Washington team’s role in this overall project has specifically been to to address the nature of offshore faults that break up the outer paert of the upper, or North American, plate, including so called “splay faults” that may play a key role in the tsunami hazard from mega-earthquakes.
Tobin and doctoral students Madeleine Lucas and Anna Ledeczi, have carried out comprehensive structural interpretation of the major splay faults and the frontal thrust zone. With our collaborators, we have published two papers detailing the results and implications of our studies, and have three others in review at prominent journals. The portion of this work that we have led has shown that the outermost (frontal) splay faults show evidence of very recent activity, indicating they slip during giant earthquakes. This would uplift the seafloor and be a part of the tsunami source displacement. Conversely, we have found that a previously hypothesized, mid-continental slope major splay fault is mostly non-existent or inactive over 100,000 year time scales, for the entire central portion of the Cascadia subduction zone. If this finding holds up, it has broad implications for the weighting of model scenarios in planning for tsunami hazard in the Oregon, Washington, and Vancouver Island regions. Additionally, we have found that frontal thrust structure, dip, and complexity varies markedly along the length of the margin. This is especially true as a first order difference between the landward-vergent wedge zone and the seaward-vergent zones, but also we have documented variability within each of these zones. We are now analyzing these results to understand their implications for likelihood of splay fault slip vs slip to the trench and other key variables in subduction zone megathrust earthquakes. This work is integrated into much broader efforts taking place by many NSF-funded researchers, the US Geological Survey, state survey entities, NOAA, and others.
This project provided the core training of two Un. of Washington doctoral students, who have had the opportunity to work closely with the US Geological Survey on the project and with academic collaborators. Because the work bears on tsunami and earthquake hazard and the processes that lead up to them, it has relevance to public safety on the west coast of the USA.
Last Modified: 12/20/2024
Modified by: Harold J Tobin
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