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Dynamically supported geoid highs over hotspots: Observation and theoryHotspots are associated with long wavelength geoid highs, an association that is even stronger when the geoid highs associated with subduction zones are removed. These associations are quantified by expanding the hotspot distribution in spherical harmonics and calculating correlation coefficients as a function of harmonic degree. The hotspot distribution spectrum is essentially white, with peaks at degrees 2 and 6. It is correlated positively with the slab residual geoid for degrees 2 to 6, with low seismic velocity in the lower mantle at degree 2, and with low seismic velocity in the upper mantle at degree 6. A variety of fluid mechanical models were tested for hotspots, including lithospheric delamination and hot plumes, by calculating their predicted dynamic geoid responses and comparing them to the observations. These models include the effects of temperature dependent rheology. The preferred hotspot model, based on observations of the geoid and seismic tomography, has plumes preferentially occurring in regions of large scale background temperature highs in a mantle with substantial viscosity increase with depth, although other models are possible.
Document ID
19860015598
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Richards, M. A. (California Inst. of Tech. Pasadena, CA, United States)
Hager, B. H. (California Inst. of Tech. Pasadena, CA, United States)
Sleep, N. H. (Stanford Univ. Calif., United States)
Date Acquired
September 5, 2013
Publication Date
January 1, 1986
Subject Category
Geophysics
Report/Patent Number
NASA-CR-176766
NAS 1.26:176766
Accession Number
86N25069
Funding Number(s)
CONTRACT_GRANT: NAG5-315
CONTRACT_GRANT: NSG-7610
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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