Sharpness of upper-mantle discontinuities determined from high-frequency reflections
Nature
By: H.M. Benz and J.E. Vidale
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Abstract
AN understanding of the nature of seismic discontinuities in the Earth's upper mantle is important for understanding mantle processes: in particular, the amplitude and sharpness of these discontinuities are critical for assessing models of upper-mantle phase changes and chemical layering. So far, seismic studies aimed at determining the thickness and lateral variability of upper-mantle discontinuities have yielded equivocal results, particularly for the discontinuity at 410km depth1,2. Here we present short-period (0.8-2.0 s) recordings of upper-mantle precursors to the seismic phase P???P??? (PKPPKP) from two South American earthquakes recorded by the ???700-station short-period array in California. Our results show that the 410- and 660-km discontinuities beneath the Indian Ocean are locally simple and sharp, corresponding to transition zones of 4 km or less. These observations pose problems for mineral physics models3-5, which predict a transitional thickness greater than 6 km for the peridotite to ??-spinel phase transition. In contrast to the results of long-period studies6,7, we observe no short-period arrivals from near 520 km depth.
Suggested Citation
Benz, H., and Vidale, J., 1993, Sharpness of upper-mantle discontinuities determined from high-frequency reflections: Nature, v. 365, no. 6442.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Sharpness of upper-mantle discontinuities determined from high-frequency reflections |
| Series title | Nature |
| Volume | 365 |
| Issue | 6442 |
| Year Published | 1993 |
| Language | English |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | Nature |