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Bradford H. Hager. Agner, Mary Alexandra Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences 2010-08-31T14:27:47Z 2010-08-31T14:27:47Z 1998 1998 http://hdl.handle.net/1721.1/57762 42519397 Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1998. Includes bibliographical references (p. 27-28). 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. by Mary Alexandra Agner. S.M. 47 p. eng Massachusetts Institute of Technology 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. http://dspace.mit.edu/handle/1721.1/7582 Earth, Atmospheric, and Planetary Sciences The effect of a low density residuum on geoid anomalies and topography Thesis application/pdf false Publication unknown unknown <Publication xmlns="https://www.openaire.eu/cerif-profile/1.1/" id="636021c3-f1ed-4158-9cc0-065420c757d6"> <Type xmlns="https://www.openaire.eu/cerif-profile/vocab/COAR_Publication_Types">http://purl.org/coar/resource_type/c_1843</Type> <Language>eng</Language> <Title>The effect of a low density residuum on geoid anomalies and topography</Title> <PublishedIn> <Publication> </Publication> </PublishedIn> <PublicationDate>1998</PublicationDate> <Authors> <Author> <DisplayName>Agner, Mary Alexandra</DisplayName> <Affiliation> <OrgUnit> </OrgUnit> </Affiliation> </Author> </Authors> <Editors> </Editors> <Publishers> <Publisher> <DisplayName>Massachusetts Institute of Technology</DisplayName> <OrgUnit /> </Publisher> </Publishers> <License>http://dspace.mit.edu/handle/1721.1/7582</License> <Keyword>Earth, Atmospheric, and Planetary Sciences</Keyword> <Abstract>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.</Abstract> <Access xmlns="http://purl.org/coar/access_right" > </Access> </Publication>