Reflectivity of the 410-km discontinuity from PP and SS precursors

Chambers, K. and Deuss, A. and Woodhouse, J. H. (2005) Reflectivity of the 410-km discontinuity from PP and SS precursors. Journal of Geophysical Research, 110, B. DOI 10.1029/2004JB003345

Text Chambers_K._Deuss_A._Woodhouse_J.H.JGR_110,B02301_(2005).pdf - Published Version Download (1MB)

Abstract

A number of studies have confirmed the global existence of a transition zone discontinuity at 410 km depth by aligning large numbers of long-period seismograms on a surface reflection phase before stacking. In particular, SS and PP precursors from the 410-km discontinuity (termed P410P and S410S) have revealed long-wavelength topography of this discontinuity. Here we extend these techniques to examine the reflection coefficient of the 410-km discontinuity. Using our measurements of P410P and S410S amplitudes, we constrain the impedance contrasts across the 410-km discontinuity. We also show lateral variations in the P wave impedance contrast at 410 km, which is typically low under North America and China and higher beneath the North Pacific. The S wave impedance contrast shows less variability on the regional scale. However, analysis of P410P and S410S amplitudes over smaller areas (by binning traces into spherical caps) shows that the S wave reflection coefficient varies over much shorter scale lengths than that for P waves. The different patterns of variation for P410P and S410S reflection amplitudes could be due to the presence of melt, water, or other chemical heterogeneities in the transition zone. Other factors such as temperature or mantle olivine content variations could also influence precursor amplitudes, but they would be expected to lead to correlated variations, and so they cannot explain all the variation that we observe.

Item Type:	Article
Additional Information:	Copyright 2005 by the American Geophysical Union.
Uncontrolled Keywords:	2005 PUBL; 2005 AREP; IA47
Subjects:	02 - Geodynamics, Geophysics and Tectonics
Divisions:	02 - Geodynamics, Geophysics and Tectonics 08 - Green Open Access
Journal or Publication Title:	Journal of Geophysical Research
Volume:	110, B
Identification Number:	10.1029/2004JB003345
Depositing User:	Sarah Humbert
Date Deposited:	01 Sep 2011 09:39
Last Modified:	10 Jul 2014 12:26
URI:	http://eprints.esc.cam.ac.uk/id/eprint/1599

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