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Interpreting D" seismic structure using synthetic waveforms computed from dynamic models

Sidorin, Igor and Gurnis, Michael and Helmberger, Donald V. and Ding, Xiaoming (1998) Interpreting D" seismic structure using synthetic waveforms computed from dynamic models. Earth and Planetary Science Letters, 163 (1-4). pp. 31-41. ISSN 0012-821X. doi:10.1016/S0012-821X(98)00172-1.

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We have formulated dynamic models of processes hypothesized to give rise to observed seismological structure at the base of the mantle. One dimensional seismic models are determined from thermo-chemical convection calculations from which synthetic waveforms are computed. Of the three scenarios studied, (1) a thermal slab, (2) a thermal slab interacting with simple chemical layer, and (3) a thermal slab interacting with a phase transition, the strength of seismic phases computed from (3) best correlates with the global geography of the observed D″ triplication. Seismic structures predicted by (1) or (2) are inconsistent with the global geography and strength of the triplication. Our successful model motivates a new class of 1-D seismic models with two mild gradients and a small discontinuity. To test this hypothesis, we searched for seismic models that both contain these features and fit D″ seismic observations. Our preferred model contains a gentle positive gradient initiated 350 km above the CMB and a 1% jump in S-velocity near 200 km. A strong negative gradient begins about 100 km above the CMB, similar to previous studies representing the lower thermal boundary layer. With the reduced first-order discontinuity, the P-wave triplication becomes too small to observe and provides a simple explanation for the observed weakness of the P in proportion to the S triplication.

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Gurnis, Michael0000-0003-1704-597X
Additional Information:© 1998 Elsevier Science B.V. Received 7 May 1998; revised version received 13 August 1998; accepted 13 August 1998. This work has been funded by the National Science Foundation Grant EAR-9629279. This represents Contribution Number 8539 of the Division of Geological and Planetary Sciences, California Institute of Technology. [RV]
Group:Seismological Laboratory
Funding AgencyGrant Number
Subject Keywords: mantle; convection; seismology; models
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Caltech Division of Geological and Planetary Sciences8539
Issue or Number:1-4
Record Number:CaltechAUTHORS:20121211-112435944
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Official Citation:Igor Sidorin, Michael Gurnis, Donald V Helmberger, Xiaoming Ding, Interpreting D″ seismic structure using synthetic waveforms computed from dynamic models, Earth and Planetary Science Letters, Volume 163, Issues 1–4, November 1998, Pages 31-41, ISSN 0012-821X, 10.1016/S0012-821X(98)00172-1. (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35910
Deposited By: Ruth Sustaita
Deposited On:11 Dec 2012 19:35
Last Modified:09 Nov 2021 23:18

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