| 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. |
| Genre: | Article |
| ProdID: | 70017357 |
| Citation Author: | Benz, H. M.; Vidale, J. E. |
| Citation Contributing Office: | |
| Citation Datum: | |
| Citation Day: | |
| Citation Edition: | |
| Citation Editor: | |
| Citation End Page: | |
| Citation Issue: | 6442 |
| Citation Keywords: | |
| Citation Language: | English |
| Citation Larger Work Title: | Nature |
| Citation LatN: | |
| Citation LatS: | |
| Citation LonE: | |
| Citation LonW: | |
| Citation Month: | |
| Citation No Pagination: | |
| Citation Number Of Pages: | |
| Citation Online Only Flag: | |
| Citation Phsyical Description: | |
| Citation Projection: | |
| Citation Public Comments: | |
| Citation Publisher: | |
| Citation Series: | |
| Citation Series Code: | |
| Citation Series Number: | |
| Citation Search Results Text: | Sharpness of upper-mantle discontinuities determined from high-frequency reflections; 1993; Article; Journal; Nature; Benz, H. M.; Vidale, J. E. |
| Citation Start Page: | |
| Citation Volume: | 365 |
| Citation Year: | 1993 |
| Type: | citation/reference |
| Text: | Sharpness of upper-mantle discontinuities determined from high-frequency reflections; 1993; Article; Journal; Nature; Benz, H. M.; Vidale, J. E. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Fri, 1 Jan 1993 00:00 -0600 |
| Publisher: | |
