Collaborative Research: Structure and Composition of Oceanic Lithosphere and the Lithosphere/Asthenosphere Boundary

Lead PI: James Gaherty

Unit Affiliation: Seismology, Geology and Tectonophysics, Lamont-Doherty Earth Observatory (LDEO)

March 2010 - February 2015
Pacific Ocean
Project Type: Research

DESCRIPTION: The lithosphere is the Earth's rocky outer shell. Lithospheric 'plates' drift over the Earth, carrying the continents, and large earthquakes and volcanic eruptions occur where the plates interact. Hence, understanding the lithosphere is central to our understanding of how the Earth works. The oceanic lithosphere, which covers some 70% of the Earth, is central to our understanding of global geodynamics and plate tectonics, but our understanding of its character (including composition and thickness) and the factors that control them is poor. Variations of seismic and electrical properties of the Earth are indicators of compositional variations. The aim of this project is to use the most up-to-date seismic and electromagnetic methods to address two fundamental questions about the lithosphere that lies beneath the Pacific basin: What factors control the seismic structure of the lithosphere, and what defines the base of the lithosphere? The broader impacts of this work include improved understanding of factors such as the composition of the lithosphere that affect volcanic eruptions, great earthquakes and tsunamis that threaten heavily populated areas in Alaska, the Pacific Northwest, and elsewhere around the Pacific Rim.

OUTCOMES: 30 of 34 OBSs were recovered successfully and the team is working to better characterize 6-hz noise that was picked up. A website has been created and an interview was published in OurAmazingPlanet.


National Science Foundation (NSF)




Woods Hole Oceanographic Institution, Brown University



Sarafian, E., R.L. Evans, J.A. Collins, J. Elsenbeck, G.A. Gaetani, J.B. Gaherty, G. Hirth and D. Lizarralde. "The electrical structure of the central Pacific upper mantle constrained by the NoMelt experiment," Geochem. Geophys. Geosyst.,, v.16, 2015. doi:doi:10.1002/2014GC005709


magneto-telluric experiments marine geology and geophysics active-source seismic refraction oceanic lithosphere ocean bottom seismographs