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Fine structure of the upper mantle

Archambeau, C. B. and Flinn, E. A. and Lambert, D. G. (1969) Fine structure of the upper mantle. Journal of Geophysical Research, 74 (25). pp. 5825-5865. ISSN 0148-0227. doi:10.1029/JB074i025p05825.

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The spectral amplitudes and travel times of seismic body waves are used to determine mantle velocity structures appropriate to distinct structural provinces within the western continental United States. In addition to basic amplitude and time data, travel-time delays and Pn velocity data from other studies are used as constraints in the systematic inversion of the data for mantle structure. The regional structures for the upper mantle determined in this manner show collectively rather sharp zones of transition (high velocity gradients) near 150, 400, 650 km and possibly near 1000 km. Comparatively, the regional structures indicate strong lateral variations in the upper mantle structure down to 150 km and possibly as deep as 200 km. The structures appropriate to the Rocky Mountain and Colorado plateau physiographic provinces show low-velocity zones capped by high-velocity lid zones, with variability in both the lid and the low-velocity zone properties from province to province and within these provinces to a much lesser degree. The mantle properties obtained for the Basin and Range contrast sharply with the plateau and mountain structures, with the lid zone being very thin or absent and abnormally low velocities extending from, or very near, the base of a thin crust to 150 km. The velocity determinations are coupled with estimates of the variation of the intrinsic dissipation function (Q) as a function of depth and frequency. These results show a pronounced low-Q zone corresponding to the average low-velocity zone depth range for the velocity models. The data suggest a frequency-dependent Q, with Q increasing with frequency. In total the results of the study strongly suggest phase transitions in the mantle, including a partially melted region corresponding to the low-velocity zone, the latter being highly variable in its properties over the region studied and strongly correlated with tectonic activity.

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Additional Information:Copyright 1969 by the American Geophysical Union. (Received March 3, 1969; revised July 18, 1969.) It is a pleasure to acknowledge the generous cooperation of John Lambert, who ably oversaw the digital data processing, and Bruce Julian, who freely made available to us his program for body-wave calculations, which we modified and used in our work. We also wish to thank our colleagues at the Seismic Data Laboratory and the Seismological Laboratory with whom we have had many beneficial discussions, and whose criticisms have sharpened our arguments in favor of the interpretations in this paper. We thank Bruce Julian, Don Anderson, and R. D. Adams for making available to us their most recent papers in advance of publication. This research was supported by the Air Force Office of Scientific Research, Office of Aerospace Research, United States Air Force, under AFSOR contracts AF-49(638)-1337 and AF 49(638)-1117 and by the Advanced Research Projects Agency, Nuclear Test Detection Office, Technical Applications Center Contract AF 33(657)-12447. Contribution 1589, Division of Geological Sciences, California Institute of Technology.
Funding AgencyGrant Number
Air Force Office of Scientific Research (AFOSR)AF-49(638)-1337
Air Force Office of Scientific Research (AFOSR)AF 49(638)-1117
Advanced Research Projects Agency (ARPA)UNSPECIFIED
Air Force Office of Scientific Research (AFOSR)AF 33(657)-12447
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Caltech Division of Geological Sciences1589
Issue or Number:25
Record Number:CaltechAUTHORS:20141107-161628904
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Official Citation:Archambeau, C. B., E. A. Flinn, and D. G. Lambert (1969), Fine structure of the upper mantle, J. Geophys. Res., 74(25), 5825–5865, doi:10.1029/JB074i025p05825.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:51469
Deposited By: George Porter
Deposited On:10 Nov 2014 16:01
Last Modified:10 Nov 2021 19:11

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