Award Abstract # 1737328
Hikurangi Trench Regional Electromagnetic Survey to Image the Subduction Thrust

NSF Org: OCE
Division Of Ocean Sciences
Recipient: THE TRUSTEES OF COLUMBIA UNIVERSITY IN THE CITY OF NEW YORK
Initial Amendment Date: March 2, 2018
Latest Amendment Date: November 5, 2020
Award Number: 1737328
Award Instrument: Continuing Grant
Program Manager: Gail Christeson
gchriste@nsf.gov
 (703)292-2952
OCE
 Division Of Ocean Sciences
GEO
 Directorate for Geosciences
Start Date: June 1, 2018
End Date: May 31, 2023 (Estimated)
Total Intended Award Amount: $1,207,620.00
Total Awarded Amount to Date: $1,227,163.00
Funds Obligated to Date: FY 2018 = $989,694.00
FY 2019 = $126,563.00

FY 2020 = $110,906.00
History of Investigator:
  • Kerry Key (Principal Investigator)
    kkey@ldeo.columbia.edu
  • Samer Naif (Former Principal Investigator)
  • Kerry Key (Former Co-Principal Investigator)
Recipient Sponsored Research Office: Columbia University
615 W 131ST ST
NEW YORK
NY  US  10027-7922
(212)854-6851
Sponsor Congressional District: 13
Primary Place of Performance: Columbia Univeristy Lamont-Doherty Earth Obs.
61 Route 9W
Palisades
NY  US  10964-8000
Primary Place of Performance
Congressional District:
17
Unique Entity Identifier (UEI): F4N1QNPB95M4
Parent UEI:
NSF Program(s): Marine Geology and Geophysics
Primary Program Source: 01001819DB NSF RESEARCH & RELATED ACTIVIT
01001920DB NSF RESEARCH & RELATED ACTIVIT

01002021DB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s): 1620
Program Element Code(s): 162000
Award Agency Code: 4900
Fund Agency Code: 4900
Assistance Listing Number(s): 47.050

ABSTRACT

The Hikurangi subduction zone (HSZ) of New Zealand is where the Pacific tectonic plate dives beneath the crust of the North Island along its eastern coast. The HSZ displays marked changes in seismicity and plate-slip along its length: to the south the plates appear to be locked and have the capacity to generate great earthquakes whereas to the north the plates are creeping and regularly host episodic slow slip events and the occasional tsunami earthquake. The physical conditions controlling this contrast in plate coupling is not well understood. Recent investigations suggest fluids may play a critical role. To delineate whether fluids act as a primary control on the style of slip expressed along the HSZ, this study will use electromagnetic (EM) methods to image the electrical resistivity structure of the HSZ. Our measurements will provide important constraints on the hydrologic architecture by quantifying the along and across-strike variations in porosity and the fluid budget of the HSZ. This project will support a Ph.D. student and several graduate students, postdocs and early career scientists will be involved in the field work. The PI is an early career scientist who will gain valuable experience leading the field project and mentoring a graduate student. Additionally, a marine EM short-course will be given for students and unfunded collaborators to learn about marine EM theory, applications, data processing, and inverse modeling.

This project will use newly proven marine EM imaging technology to constrain the porosity and fluid budget of the crust and mantle along both segments of the HSZ. The survey cruise will deploy a grid of ocean-bottom EM receivers in a 400 km by 150 km area that spans the incoming plate and fore-arc margin. Magnetotelluric (MT) response functions will be estimated from the recorded electric and magnetic field time-series. In addition, controlled-source EM (CSEM) data will be recorded by deep towing a horizontal electric dipole transmitter near the seafloor along three trench-crossing transects located in the southern, central, and northern segments of the HSZ. The MT and CSEM data will be inverted for electrical resistivity and used to quantify the porosity structure across the margin. The HSZ resistivity results will be interpreted in conjunction with existing and planned geophysical and drilling data to test the hypothesis that along-strike variations in seismicity and interplate locking are related to the fluid budget of the incoming oceanic plate, fluid content along the plate interface, and upper plate permeability/porosity structure. The MT data will also image the electrical resistivity of the lithosphere and asthenosphere, providing independent constraints on the origin of the lithosphere-asthenosphere boundary.

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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Chesley, Christine and Naif, Samer and Key, Kerry and Bassett, Dan "Fluid-rich subducting topography generates anomalous forearc porosity" Nature , v.595 , 2021 https://doi.org/10.1038/s41586-021-03619-8 Citation Details

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.

1)    We conducted the largest marine EM survey at a subduction zone to date. This culminates in the largest amphibious EM dataset to date when combined with the hundreds of onshore MT sites collected by GNS Science of New Zealand.

2)    We successfully acquired MT data at 168 stations and CSEM data at 136 of those stations, spanning the majority of the Hikurangi margin.

3)    Analysis of the northern profile led to two major discoveries: a) the rough topography of a subducting seamount generates highly porous damage zones in the upper plate forearc where microseismicity is concentrated; b) a large seamount on the incoming plate holds approximately 3­x–5x more water than typical oceanic crust, adding a substantial volume to the flux of water that is input at subduction zones. More generally, the electrical structure is highly heterogeneous, which is consistent with other geophysical observations, suggesting that structural heterogeneity may be responsible for why the northern half of Hikurangi experience repeating shallow slow-slip events.

4)    Analysis of the southern profile found far more homogeneous electrical structure, where the porosity of the incoming plate and accretionary prism is primarily controlled by compaction due to overburden. This supports the hypothesis that structural heterogeneity is an important control on plate coupling and the prevalence of slow-slip events versus stick-slip earthquakes, where the southern half of Hikurangi margin is locked and accumulating stress that may be released in a future earthquake. The analysis further showed enhanced compaction starting 25 km seaward of the deformation front (i.e., trench axis), possibly due to horizontal stresses that delineate the development of a proto-thrust zone. In the near-surface, resistive structures indicate the presence of abundant gas hydrates, consistent with prior studies using seismic reflection imaging.

 


Last Modified: 10/30/2023
Modified by: Kerry Key

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