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Subduction, back-arc spreading and global mantle flow

Hager, Bradford H. and O'Connell, Richard J. and Raefsky, Arthur (1983) Subduction, back-arc spreading and global mantle flow. Tectonophysics, 99 (2-4). pp. 165-189. ISSN 0040-1951. https://resolver.caltech.edu/CaltechAUTHORS:20171120-155732622

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Abstract

The shapes and orientations of Benioff zones beneath island arcs, interpreted as marking the location of subducted lithosphere, provide the best presently available constraints on the global convective flow pattern associated with plate motions. This global flow influences the dynamics of subduction. Subduction zone phenomena therefore provide powerful tests for models of mantle flow. We compute global flow models which, while simple, include those features which are best constrained, namely the observed plate velocities, applied as boundary conditions, and the density contrasts given by thermal models of the lithosphere and subducted slabs. Two viscosity structures are used; for one, flow is confined to the upper mantle, while for the other, flow extends throughout the mantle. Instantaneous flow velocity vectors match observed Benioff zone dips and shapes for the model which allows mantle-wide flow but not for the upper mantle model, which has a highly contorted flow pattern. The effect of trench migration on particle trajectories is calculated; it is not important if subduction velocities are greater than migration rates. Two-dimensional finite element models show that including a coherent high viscosity slab does not change these conclusions. A coherent high viscosity slab extending deep into the upper mantle would significantly slow subduction if flow were confined to the upper mantle. The maximum earthquake magnitude, M_w, for island arcs correlates well with the age of the subducted slab and pressure gradient between the trench and back-arc region for the whole mantle, but not the upper mantle, flow model. The correlations with orientations of Benioff zones and seismic coupling strongly suggest that the global return flow associated with plate motions extends below 700 km. For both models, regions of back-arc spreading have asthenospheric shear pulling the back-arc toward the trench; regions without back-arc spreading have the opposite sense of shear, suggesting global flow strongly influences back-arc spreading.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/0040-1951(83)90101-4DOIArticle
http://www.sciencedirect.com/science/article/pii/0040195183901014PublisherArticle
ORCID:
AuthorORCID
Hager, Bradford H.0000-0002-5643-1374
Additional Information:© 1983 Elsevier B.V. Revised October 7, 1981; received by Publisher May 19, 1983. This work was supported by NSF grants EAR78-16321, EAR78-15184, EAR80-25643, NASA grant NSG-7610, and by an NSF graduate fellowship. We thank Frank Richter, Larry Ruff, Phil England and Don Anderson for stimulating discussions, and Glyn Jones and Geoff Davies for review. Contribution No. 3678, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, 91125.
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
NSFEAR78-16321
NSFEAR78-15184
NSFEAR80-25643
NASANSG-7610
NSF Graduate Research FellowshipUNSPECIFIED
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Caltech Division of Geological and Planetary Sciences3678
Issue or Number:2-4
Record Number:CaltechAUTHORS:20171120-155732622
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20171120-155732622
Official Citation:Bradford H. Hager, Richard J. O'Connell, Arthur Raefsky, Subduction, back-arc spreading and global mantle flow, In Tectonophysics, Volume 99, Issues 2–4, 1983, Pages 165-189, ISSN 0040-1951, https://doi.org/10.1016/0040-1951(83)90101-4. (http://www.sciencedirect.com/science/article/pii/0040195183901014)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:83370
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:21 Nov 2017 00:06
Last Modified:09 Mar 2020 13:18

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