Award Abstract # 1658491
Collaborative Research: Imaging small-scale convection and structure of the mantle in the south Pacific: a US contribution to international collaboration PacificArray

NSF Org: OCE
Division Of Ocean Sciences
Recipient: THE TRUSTEES OF COLUMBIA UNIVERSITY IN THE CITY OF NEW YORK
Initial Amendment Date: August 14, 2017
Latest Amendment Date: August 4, 2020
Award Number: 1658491
Award Instrument: Continuing Grant
Program Manager: Deborah K. Smith
OCE
 Division Of Ocean Sciences
GEO
 Directorate For Geosciences
Start Date: August 15, 2017
End Date: October 31, 2020 (Estimated)
Total Intended Award Amount: $516,396.00
Total Awarded Amount to Date: $516,396.00
Funds Obligated to Date: FY 2017 = $92,194.00
FY 2018 = $71,161.00

FY 2020 = $0.00
History of Investigator:
  • James Gaherty (Principal Investigator)
    james.gaherty@nau.edu
  • Goran Ekstrom (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: Lamont-Doherty Earth Observatory
61 Route 9W
Palisades
NY  US  10964-1707
Primary Place of Performance
Congressional District:
17
Unique Entity Identifier (UEI): F4N1QNPB95M4
Parent UEI:
NSF Program(s): Marine Geology and Geophysics,
OCE SPECIAL PROGRAMS
Primary Program Source: 01001718DB NSF RESEARCH & RELATED ACTIVIT
01001819DB NSF RESEARCH & RELATED ACTIVIT

01002021DB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s):
Program Element Code(s): 1620, 5418
Award Agency Code: 4900
Fund Agency Code: 4900
Assistance Listing Number(s): 47.050

ABSTRACT

All deformation on the surface of Earth, including faulting responsible for earthquakes, is produced by the motion of tectonic plates. It is widely accepted that thermal convection in the mantle drives plate motion, but details of that convection and how exactly it moves the plates are poorly understood. Oceanic plates make up 70% of the Earth's surface and offer important windows into mantle convection, yet they are largely unexplored due to the lack of seismic data from the ocean basins. Questions abound regarding the thermal structure of oceanic plates, the significance of volcanism in the middle of oceanic plates, and how the convecting mantle beneath the plates controls their movements. Waves in the gravity field and un-explained shallowing of the ocean floors hint at small-scale convection beneath the oceanic plates. This project contributes to an international effort to strategically place temporary arrays of instruments across the Pacific Ocean basin that record the energy from earthquakes. Recent community advances in ocean bottom seismographs will be used to record unique datasets in locations where large gaps in coverage exist today. These data will allow us to infer deformation and variations in mantle temperature related to small-scale convection. As part of the international collaboration, all data will be openly available to scientists worldwide. The project supports the training of graduate and undergraduate students.

This project will collect 12-15 months of broadband ocean bottom seismograph (OBS) data in two 30-station arrays in the central and southern Pacific. These arrays, deployed at two distinct plate ages (~30 Ma and ~120 Ma), will address specific critical questions on the dynamics of the oceanic asthenosphere, including its underlying state (temperature, presence of melt, water or other volatiles, and deformation mechanism). The arrays are designed to image the anisotropic velocity signature of small-scale convection, which has been invoked to explain the flattening of the age versus depth curve in old ocean plates, 140-200 km wavelength gravity lineations, and ubiquitous off-axis, non-plume volcanism observed at a variety of scales. Anisotropic surface wave and body wave tomographic models will be supplemented by shear wave splitting and attenuation measurements to obtain a multi-faceted understanding of the asthenosphere and base of the plates. Finally, the order-of-magnitude increases in path coverage for surface and body waves in the south-central Pacific will enable new advances in global tomography.

PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH

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Russell, Joshua B. and Eilon, Zachary and Mosher, Stephen G. "OBSrange: A New Tool for the Precise Remote Location of Ocean?Bottom Seismometers" Seismological Research Letters , 2019 https://doi.org/10.1785/0220180336 Citation Details

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