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An Earth Model Based on Free Oscillations and Body Waves

Anderson, Don L. and Hart, Robert S. (1976) An Earth Model Based on Free Oscillations and Body Waves. Journal of Geophysical Research, 81 (8). pp. 1461-1475. ISSN 0148-0227. doi:10.1029/JB081i008p01461.

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Several recent inversion studies have clearly indicated the lack of resolving power of the normal mode data set and the possible trade-offs among the various parameters. These studies have also shown that the final model is as dependent on the starting model as on the data set. It is therefore important to incorporate body wave data into any inversion scheme not only to gain resolution but also to reduce trade-offs between density and velocity. An earth model based on special studies of the structure of the mantle and core is inverted to be consistent with both body wave data and a representative set of normal mode observations (437 modes). The resulting model has a 40-km-thick upper mantle lithospheric lid terminating at 61 km, with high density (3.5 g/cm^3) and seismic velocities (8.38 and 4.71 km/s), a pronounced upper mantle low-velocity zone (LVZ) of 180-km thickness, and transition regions of rapid velocity increase at 375–425, 500–550, and 650–675 km. There are also anomalous gradients between 700 and 1200 km. This model, C2, is slow by about 0.6 and 2–4 s for P and S waves, respectively, in comparison with body wave solutions which have a greater continental bias. The major features of the upper mantle can be explained by partial melting (LVZ) and the successive transformation of an olivine-pyroxene mantle to β spinel, γ spinel, and garnet and further phase changes below 750 km. In addition to the radial inhomogeneities in the upper mantle there is evidence for inhomogeneity at the base of the mantle, the top of the core, and the regions on each side of the outer core-inner core boundary.

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Additional Information:© 1976 by the American Geophysical Union. Received June 9, 1975; revised October 14, 1975; accepted November 7, 1975. Article first published online: 20 Sep 2012. This research was supported by the Advanced Research Projects Agency of the Department of Defense and was monitored by the Air Force Office of Scientific Research under contract F44620-72-C-0078. Tom Jordan participated extensively in the early part of this study, and we are indebted to him for much advice. We would like to thank F. Gilbert, A. Dziewonski, D. Helmberger, and B. Bolt for preprints of their papers. Conversations with Martin Smith and Freeman Gilbert were quite helpful. One of us (R.S.H.) thanks the National Science Foundation for graduate fellowship support. Contribution 2637 of the Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125.
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Advanced Research Projects Agency (ARPA)UNSPECIFIED
Air Force Office of Scientific Research (AFOSR)F44620-72-C-0078
NSF Graduate FellowshipUNSPECIFIED
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Caltech Division of Geological and Planetary Sciences2637
Issue or Number:8
Record Number:CaltechAUTHORS:20150220-071738980
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Official Citation:Anderson, D. L., and R. S. Hart (1976), An Earth Model based on free oscillations and body waves, J. Geophys. Res., 81(8), 1461–1475, doi:10.1029/JB081i008p01461.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:55038
Deposited By: Ruth Sustaita
Deposited On:20 Feb 2015 16:02
Last Modified:10 Nov 2021 20:40

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