Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

The Nature of the 660-Kilometer Upper-Mantle Seismic Discontinuity from Precursors to the PP Phase

Charles H. Estabrook and Rainer Kind
Science
New Series, Vol. 274, No. 5290 (Nov. 15, 1996), pp. 1179-1182
Stable URL: http://www.jstor.org/stable/2891589
Page Count: 4
  • More info
  • Cite this Item
The Nature of the 660-Kilometer Upper-Mantle Seismic Discontinuity from Precursors to the PP Phase
Preview not available

Abstract

Global Seismic data were used to image upper-mantle seismic discontinuities. Stacks of phases that precede the PP Phase, thought to be underside reflections from the upper-mantle discontinuities at depths of 410 and 660 kilometers, show that the reflection from 410 kilometers is present, but the reflection from 660 kilometers is not observed. A continuous Lamé's constant λ and seismic parameter at the 660-kilometer discontinuity explain the missing underside P reflections and lead to a P-wave velocity jump of only 2 percent, whereas the S-wave velocity and density remain unchanged with respect to previous global models. The model deemphasizes the role of Lamé's constant λ with regard to the shear modulus and constrains the mineralogical composition across the discontinuity.

Page Thumbnails

  • Thumbnail: Page 
1179
    1179
  • Thumbnail: Page 
1180
    1180
  • Thumbnail: Page 
1181
    1181
  • Thumbnail: Page 
1182
    1182