| NSF Org: |
OCE Division Of Ocean Sciences |
| Recipient: |
|
| Initial Amendment Date: | October 23, 2018 |
| Latest Amendment Date: | May 13, 2021 |
| Award Number: | 1827452 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Joseph Carlin
OCE Division Of Ocean Sciences GEO Directorate for Geosciences |
| Start Date: | November 1, 2018 |
| End Date: | October 31, 2022 (Estimated) |
| Total Intended Award Amount: | $749,555.00 |
| Total Awarded Amount to Date: | $768,064.00 |
| Funds Obligated to Date: |
FY 2021 = $18,509.00 |
| History of Investigator: |
|
| Recipient Sponsored Research Office: |
615 W 131ST ST NEW YORK NY US 10027-7922 (212)854-6851 |
| Sponsor Congressional District: |
|
| Primary Place of Performance: |
61 Route 9W Palisades NY US 10964-8000 |
| Primary Place of
Performance Congressional District: |
|
| Unique Entity Identifier (UEI): |
|
| Parent UEI: |
|
| NSF Program(s): | Marine Geology and Geophysics |
| Primary Program Source: |
01002122DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): |
|
| Program Element Code(s): |
|
| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
At the Cascadia Subduction Zone, the slow ongoing descent of the Juan de Fuca plate beneath the northwestern coast of North America has generated large earthquakes and associated tsunami in the past. Geologic records suggest that some sections of the subduction zone fault or "megathrust", which extends ~35-90 miles seaward from the coasts of northern California all the way to southern British Columbia, slipped less than other sections during the last large earthquake (1700 AD), and that in some prior EQ only parts of the subduction zone ruptured. Whether these along-margin variations may persist in future EQ has important implications for quantifying earthquake and tsunami hazards within the heavily populated Pacific Northwest margin. Geologic structure such as seamounts and other topographic features in the descending Juan de Fuca plate, the structure and properties of the thick folded and faulted package of sediments that forms above the subduction zone fault, or the properties of megathrust fault rocks, could contribute to these along-margin variations. However the current observations are limited and allow for a wide range of possible future earthquake scenarios. Modern marine seismic reflection imaging techniques provide the best tools available for illuminating a subduction zone to the depths of the earthquake source region and below. The overall goal of this project is to acquire a regional grid of modern marine seismic reflection data spanning the entire Cascadia Subduction zone to image how the geologic structure and properties of this subduction zone vary both along and across the margin. This project will serve the national interest in that the acquired data will form a foundational dataset for future initiatives focused on hazard assessment in the U.S. Pacific Northwest, including for an earthquake early warning network and deep drilling to sample the fault zone rocks, and it will promote the advancement of science by providing a new regional framework relevant for the wide range of multi-disciplinary onshore and offshore studies conducted in this region over the past several decades.
Specifically, this study will use ultra-long-offset multi-channel seismic (MCS) data to characterize subducting plate and accretionary wedge structure, and properties of the megathrust, to address the following specific questions: 1. Are there any systematics in the structure and properties of the incoming Juan de Fuca plate, the megathrust zone, and accretionary wedge associated with inferred paleo-rupture segmentation? 2. Are there down-dip variations in megathrust geometry and reflectivity indicative of transitions in fault properties, and what are the properties of the potentially tsunamigenic shallow portion of the megathrust? Long 15-km-offset MCS data will be acquired along twenty 2-D profiles at 50-100 km spacing oriented perpendicular to the margin and located to provide coverage in areas inferred to be paleo-rupture patches and their boundary zones. The survey will also include one continuous strike line along the continental shelf centered roughly over gravity-inferred fore-arc basins to investigate possible segmentation near the down-dip limit of the seismogenic zone. The margin normal lines will extend approximately 50 km seaward of the deformation front to image the region of subduction bend faulting in the incoming oceanic plate, and landward of the deformation front to as close to the shoreline as can be safely maneuvered. The acquired data will be designed to characterize 1) the deformation and topography of the incoming plate, 2) the depth, topography and reflectivity of the megathrust, 3) sediment properties and amount of sediment subduction, 4) the structure and evolution of the accretionary wedge, including geometry and reflectivity of fault networks, and how these properties vary along strike, spanning the full length of the margin and down dip across what may be the full width of the seismogenic zone at Cascadia. The data will be processed to pre-stack depth migration using state-of-the art seismic processing techniques and will be made openly available to the community, providing a high-quality data set illuminating the regional subsurface architecture all along the Cascadia Subduction Zone.
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.
At the Cascadia Subduction Zone, the slow ongoing descent of the Juan de Fuca plate beneath the northwestern coast of North America has generated large earthquakes (EQ) and associated tsunami in the past. Geologic records suggest that some sections of the subduction zone fault or ?megathrust?, which extends ~35-90 miles seaward from the coasts of northern California all the way to southern British Columbia, slipped less than other sections during the last large earthquake (1700 AD), and that in some prior EQ only parts of the subduction zone ruptured. Whether these along-margin variations may persist in future EQ has important implications for quantifying earthquake and tsunami hazards within the heavily populated Pacific Northwest margin. Geologic structure such as seamounts and other topographic features in the descending Juan de Fuca plate, the structure and properties of the thick folded and faulted package of sediments that forms above the subduction zone fault, or the properties of megathrust fault rocks, could all contribute to these along-margin variations. However, the current observations are limited and allow for a wide range of possible future earthquake scenarios. Modern marine seismic reflection imaging techniques provide the best tools available for illuminating a subduction zone to the depths of the earthquake source region and below but to date little of these data have been acquired at Cascadia.
The overall goal of the Cascadia Seismic Imaging Experiment 2021- CASIE21 was to acquire and process a regional grid of modern marine seismic reflection data from the Cascadia Subduction zone to image how the geologic structure and properties of this subduction zone vary both along and across the margin. In support of this project, in summer of 2021 we made use of the advanced seismic imaging capabilities of the Research Vessel Marcus G Langseth to acquire a total of 5347 line kilometers of deep penetration, high resolution Multi-Channel Seismic (MCS) data. The CASIE21-MCS data were acquired on 18 primary margin perpendicular lines spaced 50-75 km apart and 6 partial margin parallel lines spanning the subduction zone from the north Gorda plate to offshore Vancouver Island near the Nootka fault zone. While we experienced a number of challenges during the expedition due to equipment problems and poor weather, over 80% of the planned data coverage was acquired and the majority of cruise objectives were met. Following data acquisition, advanced data processing techniques were used to process the data to pre-stack depth migration including for removal of noise and multiple reflected energy, and for determining detailed seismic wavespeed models needed to locate the reflections beneath the seafloor in depth. The final CASIE21 processed data set reveals excellent imaging of the oceanic plate and overriding sediment blanket prior to subduction, of the actively forming accretionary wedge within the Washington portion of the margin, top of the downgoing oceanic plate and the base of oceanic crust all along the margin, as well as new constraints on the location of the plate boundary fault at Cascadia. The dataset is allowing for construction of new maps of the Cascadia plate interface along the margin which can be used for next generation models of Cascadia subduction zone earthquake and tsunami sources. This project will serve the national interest in that the acquired data will provide a foundational dataset for future initiatives focused on hazard assessment in the Pacific Northwest, and it will promote the advancement of science by providing a new regional framework relevant for the range of multi-disciplinary onshore and offshore studies conducted in this region over the past several decades.
Last Modified: 01/31/2023
Modified by: Suzanne M Carbotte
Please report errors in award information by writing to: awardsearch@nsf.gov.
