The effect of a low density residuum on geoid anomalies and topography

Recent seismological measurements of the Pacific oceanic structure have detected a positive correspondence between surface topography, seismic wave speed, and the geoid (gravitational potential). High seismic wave speed indicates cold material sinking, which pulls the surface downward. Thus, topographic lows are expected to correlate with seismic wave speed highs, contrary to the new seismic measurements. We propose models which include two segregated materials, representing the fertile upper mantle and the residue from crustal melting, in order to decouple the surface topography from subsurface convection and create a positive correlation between topography and wave speed. We add a low viscosity zone beneath the residue to enhance the density contribution to the geoid anomaly and ensure that its sign is in phase with that of the surface topography and wave speed. Our models produce surface topography and geoid anomalies comparable to the recent seismological measurements. These models offer constraints on the strength of the low viscosity zone as well as the density difference between the residue and the upper mantle.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Earth, Atmospheric, and Planetary Sciences

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

1998

Author dc:creator

• Agner, Mary Alexandra

Advisor dc:contributor.advisor

• Bradford H. Hager.

• Earth, Atmospheric, and Planetary Sciences

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/57762

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/57762