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Lower mantle tomography and phase change mapping

Sun, Daoyuan and Helmberger, Don (2008) Lower mantle tomography and phase change mapping. Journal of Geophysical Research B, 113 (B10). Art. No. B10305. ISSN 0148-0227. http://resolver.caltech.edu/CaltechAUTHORS:SUNjgrb08

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Abstract

A lower mantle S wave triplication (Scd) has been recognized for many years and appears to be explained by the recently discovered perovskite (PV) to postperovskite (PPV) phase change. Seismic observations of Scd display (1) rapid changes in strength and timing relative to S and ScS and (2) early arrivals beneath fast lower mantle regions. While the latter feature can be explained by a Clapeyron slope (λ) of 6 MPa/K and a velocity jump of 1.5% when corrected by tomographic predictions, it does not explain the first feature. Here, we expand on this mapping approach by attempting a new parameterization that requires a sample of D" near the ScS bounce point (δ VS) where the phase height (hph) and velocity jump (β) are functions of (δ VS). These parameters are determined by modeling dense record sections collected from USArray and PASSCAL data where Grand's tomographic model is the most detailed in D" structure beneath Central America. We also address the range of λ to generate new global models of the phase boundary and associated temperature variation. We conclude that a λ near 9 MPa/K is most satisfactory but requires β to be nonuniform with a range from about 1.0 to 4.0% with some slow region samples requiring the largest values. Moreover, the edges of the supposed buckled slabs delimitated by both P and S waves display very rapid changes in phase boundary heights producing Scd multipathing. These features can explain the unstable nature of the Scd phase with easy detection to no detection commonly observed. The fine structure at the base of the mantle beneath these edges contains particularly strong reflections indicative of local ultralow velocity zones, which are predicted in some dynamic models.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1029/2007JB005289DOIArticle
ORCID:
AuthorORCID
Sun, Daoyuan0000-0003-4461-4664
Additional Information:© 2008 by the American Geophysical Union. Received 23 July 2007; accepted 3 July 2008; published 7 October 2008. We would like to thank two reviewers and the Associate Editor. Their suggestions and comments were greatly appreciated and made significant improvements to the manuscript. We also thank discussion with Mike Gurnis and Eh Tan. Data were provided by IRIS data centers, Canadian National Seismograph Network, and POLARIS Network. All maps in this paper were produced using GMT developed by Paul Wessel and Walter H. F. Smith. This work was supported by National Science Foundation grants EAR-0456433 and 0639507. Contribution number 10005 of the Division of Geological and Planetary Sciences, California Institute of Technology.
Funders:
Funding AgencyGrant Number
NSFEAR-0456433
NSFEAR-0639507
Subject Keywords:WAVE VELOCITY STRUCTURE; BENEATH CENTRAL-AMERICA; DEEP MANTLE; LATERAL VARIATIONS; D'' DISCONTINUITY; THERMAL STRUCTURE; SEISMIC EVIDENCE; COCOS PLATE; P-WAVE; BOUNDARY
Issue or Number:B10
Record Number:CaltechAUTHORS:SUNjgrb08
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:SUNjgrb08
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13395
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:26 Feb 2009 01:39
Last Modified:02 Oct 2017 19:05

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