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  • 1
    Online Resource
    Online Resource
    Crustal structure along the southern Central American volcanic front : CENTRAL AMERICAN VOLCANIC FRONT CRUSTAL STRUCTURE
    American Geophysical Union (AGU) ; 2008
    In:  Geochemistry, Geophysics, Geosystems Vol. 9, No. 8 ( 2008-08), p. n/a-n/a
    Details
    In: Geochemistry, Geophysics, Geosystems, American Geophysical Union (AGU), Vol. 9, No. 8 ( 2008-08), p. n/a-n/a
    Type of Medium: Online Resource
    ISSN: 1525-2027
    URL: Article
    DOI: 10.1029/2008GC001991
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2008
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  • 2
    Online Resource
    Online Resource
    The influence of plate motions on three‐dimensional back arc mantle flow and shear wave splitting
    American Geophysical Union (AGU) ; 2000
    In:  Journal of Geophysical Research: Solid Earth Vol. 105, No. B12 ( 2000-12-10), p. 28009-28033
    Details
    In: Journal of Geophysical Research: Solid Earth, American Geophysical Union (AGU), Vol. 105, No. B12 ( 2000-12-10), p. 28009-28033
    Abstract: Both the polarization direction of the fast shear waves and the types of deformation within overriding plates vary between the back arc basins of western Pacific subduction zones. The goal of this study is to test the possibility that motions of the overriding plates may control the patterns of seismic anisotropy and therefore the observed shear wave splitting. We calculated three‐dimensional models of viscous asthenospheric flow driven by the motions of the subducting slab and overriding plates. Shear wave splitting was calculated for polymineralic anisotropy within the back arc mantle wedge assuming that the anisotropy was created by flow‐induced strain. Predicted splitting may differ substantially depending on whether anisotropy is computed directly using polycrystalline plasticity models or is based on the orientation of finite strain. A parameter study shows that both finite strain and textural anisotropy developed within three‐dimensional, plate‐coupled asthenospheric flow models are very heterogeneous when back arc shearing occurs within the overriding plate. Therefore predicted shear wave splitting varies strongly as a function of plate motion boundary conditions and with ray path through the back arc asthenosphere. Flow models incorporating plate motion boundary conditions for the Tonga, southern Kuril, and eastern Aleutian subduction zones produce splitting parameters consistent with observations from each region. Trench‐parallel flow generated by small variations in the dip of the subducting plate may be important in explaining observed fast directions of anisotropy sampled within the innermost corner of the mantle wedge.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2000JB900297
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2000
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    detail.hit.zdb_id: 3094268-8
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    SSG: 16,13
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  • 3
    Online Resource
    Online Resource
    Shear wave splitting, continental keels, and patterns of mantle flow
    American Geophysical Union (AGU) ; 2000
    In:  Journal of Geophysical Research: Solid Earth Vol. 105, No. B3 ( 2000-03-10), p. 6255-6275
    Details
    In: Journal of Geophysical Research: Solid Earth, American Geophysical Union (AGU), Vol. 105, No. B3 ( 2000-03-10), p. 6255-6275
    Abstract: In this study we investigated the origin of seismic anisotropy in the mantle beneath North America. In particular, we evaluated whether shear wave splitting patterns in eastern North America are better explained by anisotropy caused by lithospheric deformation, anisotropy due to mantle flow beneath the lithosphere, or a combination of both. We examined new measurements of shear wave splitting from the Missouri to Massachusetts broadband seismometer array (MOMA), the North American Mantle Anisotropy and Discontinuity experiment (NOMAD), as well as splitting parameters from several previous studies. We developed a simple finite difference model that approximates mantle flow around a complex, three‐dimensional continental lithospheric keel. To evaluate potential anisotropy from mantle flow beneath the lithosphere in eastern North America, we compared shear wave splitting observations to predicted splitting parameters calculated using this mantle flow model. Our results indicate that a significant portion of observed shear wave splitting in eastern North America can be explained by mantle flow around the continental keel. However, shear wave splitting patterns in a few regions of eastern North America indicate that a component of lithospheric anisotropy must exist, particularly in regions containing the largest keel thicknesses. For eastern North America, as well as for splitting observations in Australia, Europe, and South America, we favor a model in which anisotropy is controlled by a combination of both lithospheric deformation and subcontinental mantle flow.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/1999JB900372
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2000
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    detail.hit.zdb_id: 161665-1
    detail.hit.zdb_id: 3094268-8
    detail.hit.zdb_id: 710256-2
    detail.hit.zdb_id: 2016804-4
    detail.hit.zdb_id: 3094181-7
    detail.hit.zdb_id: 3094219-6
    detail.hit.zdb_id: 3094167-2
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    SSG: 16,13
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  • 4
    Online Resource
    Online Resource
    Slicing into the earth
    American Geophysical Union (AGU) ; 1996
    In:  Eos, Transactions American Geophysical Union Vol. 77, No. 48 ( 1996-11-26), p. 477-481
    Details
    In: Eos, Transactions American Geophysical Union, American Geophysical Union (AGU), Vol. 77, No. 48 ( 1996-11-26), p. 477-481
    Abstract: Regional arrays of seismometers provide a powerful means of mapping the details of deep‐Earth structure. Our understanding of the geological processes at work within our planet depends on our ability to examine them; seismic techniques remain the best tool available. However, spatial aliasing due to the less‐than‐optimal distribution of global seismometers has long made it difficult to determine deep‐Earth structure from teleseismic waves. The temporary deployment of portable broadband seismometers can help by providing high‐resolution windows into the Earth. Patterns of global mantle convection create seismically observable features such as anisotropy at the top and bottom of the mantle, topography of upper mantle discontinuities, and heterogeneous structure at the core‐mantle boundary.
    Type of Medium: Online Resource
    ISSN: 0096-3941 , 2324-9250
    URL: Article
    DOI: 10.1029/96EO00317
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1996
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    SSG: 16,13
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  • 5
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    Online Resource
    Multi‐Layer Seismic Anisotropy Beneath Greenland
    American Geophysical Union (AGU) ; 2021
    In:  Geochemistry, Geophysics, Geosystems Vol. 22, No. 5 ( 2021-05)
    Details
    In: Geochemistry, Geophysics, Geosystems, American Geophysical Union (AGU), Vol. 22, No. 5 ( 2021-05)
    Abstract: A total of 299 new teleseismic shear‐wave splitting measurements have been made using broadband stations across Greenland Variations in splitting fast direction with back‐azimuth can be explained by two layers of mantle anisotropy which are consistent across Greenland The lower layer of anisotropy is consistent with asthenospheric shear or accreted lithosphere; the upper layer is consistent with past lithospheric orogenic deformation
    Type of Medium: Online Resource
    ISSN: 1525-2027 , 1525-2027
    URL: Article
    DOI: 10.1029/2020GC009512
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2021
    detail.hit.zdb_id: 2027201-7
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  • 6
    Online Resource
    Online Resource
    Modeling anisotropy and plate‐driven flow in the Tonga subduction zone back arc
    American Geophysical Union (AGU) ; 2000
    In:  Journal of Geophysical Research: Solid Earth Vol. 105, No. B7 ( 2000-07-10), p. 16181-16191
    Details
    In: Journal of Geophysical Research: Solid Earth, American Geophysical Union (AGU), Vol. 105, No. B7 ( 2000-07-10), p. 16181-16191
    Abstract: The goal of this study is to determine whether shear wave splitting observed in subduction zone back arc regions, the Tonga subduction zone in particular, can be quantitatively modeled with flow in the back arc mantle driven by the motions of the subducting slab and the upper back arc plate. We calculated two‐dimensional mantle flow models using known Tonga plate motions as boundary conditions and assuming a range of uniform and variable viscosity structures. Shear wave splitting was predicted for the anisotropy due to lattice preferred orientation (LPO) of olivine and orthopyroxene in the flow model finite strain fields. The predicted shear wave splitting provides a good match to the fast directions (parallel to the azimuth of subducting plate motion) and splitting times (0.5–1.5 s) observed in Tonga, both for models where LPO anisotropy develops everywhere above 410 km and for models where LPO anisotropy is confined to regions of relatively high stress. If LPO anisotropy does develop over the entire upper 410 km of the mantle, the strength of anistropy induced by a given amount of shear strain must be relatively weak (∼4% for shear strains of 1.5, with a maximum value of ∼6% for very large strains). The splitting observations are comparably fit by a wide range of different viscosity models. Anisotropy due to melt‐filled cracks aligned by stresses in the back arc flow models predicts fast directions roughly normal to observed values and thus cannot alone explain the observed splitting.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/1999JB900441
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2000
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    SSG: 16,13
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  • 7
    Online Resource
    Online Resource
    Seismic amplitude modeling and the shallow crustal structure of the East Pacific Rise at 12°N
    American Geophysical Union (AGU) ; 1986
    In:  Journal of Geophysical Research: Solid Earth Vol. 91, No. B14 ( 1986-12-10), p. 14006-14014
    Details
    In: Journal of Geophysical Research: Solid Earth, American Geophysical Union (AGU), Vol. 91, No. B14 ( 1986-12-10), p. 14006-14014
    Abstract: Velocity structures of the upper 2 km of the oceanic crust were used to model seismic refraction data collected on the eastern flank of the East Pacific Rise at 12°N during the Rivera Ocean Seismic Experiment (ROSE). Data, generated with a Bolt 1500C air gun source, show multiple narrow ( 〈 1 km in range) peaks in the amplitude of the first refracted arrival. Record sections separated by as much as 150 km indicate similar amplitude versus range patterns, suggesting that the amplitude peaks are caused by consistent structural features and not by random crustal inhomogeneities. These amplitude highs do not consistently correlate with seafloor bathymetry and hence cannot be explained solely by topographic focussing of seismic energy. Through travel time analysis and ray tracing we find a crustal velocity model with two vertical zones of concave gradients which focus rays at 6 and 8 km range. Synthetic seismograms and power versus range patterns computed for this model by the reflectivity algorithm are consistent with the two peak amplitude pattern observed on nearly all air gun record sections. These results suggest that the vertical gradient zone structure of the uppermost 2–3 km of ocean crust is continuous to first order over the ROSE area.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/JB091iB14p14006
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1986
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    detail.hit.zdb_id: 161667-5
    detail.hit.zdb_id: 2969341-X
    detail.hit.zdb_id: 161665-1
    detail.hit.zdb_id: 3094268-8
    detail.hit.zdb_id: 710256-2
    detail.hit.zdb_id: 2016804-4
    detail.hit.zdb_id: 3094181-7
    detail.hit.zdb_id: 3094219-6
    detail.hit.zdb_id: 3094167-2
    detail.hit.zdb_id: 2220777-6
    detail.hit.zdb_id: 3094197-0
    SSG: 16,13
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  • 8
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    The meaning of midlithospheric discontinuities: A case study in the northern U.S. craton
    American Geophysical Union (AGU) ; 2015
    In:  Geochemistry, Geophysics, Geosystems Vol. 16, No. 12 ( 2015-12), p. 4057-4083
    Details
    In: Geochemistry, Geophysics, Geosystems, American Geophysical Union (AGU), Vol. 16, No. 12 ( 2015-12), p. 4057-4083
    Abstract: Northern U.S. cratonic mantle discontinuities are imaged by Sp converted waves Four distinct classes of lithospheric discontinuity are observed Cratonic mantle grew by subduction‐related processes, at least in Proterozoic
    Type of Medium: Online Resource
    ISSN: 1525-2027 , 1525-2027
    URL: Issue
    URL: Article
    DOI: 10.1002/ggge.v16.12
    DOI: 10.1002/2015GC006030
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2015
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  • 9
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    Seismic anisotropy above and below the subducting Nazca lithosphere in southern South America : SEISMIC ANISOTROPY AT THE NAZCA SLAB
    American Geophysical Union (AGU) ; 2012
    In:  Journal of Geophysical Research: Solid Earth Vol. 117, No. B12 ( 2012-12), p. n/a-n/a
    Details
    In: Journal of Geophysical Research: Solid Earth, American Geophysical Union (AGU), Vol. 117, No. B12 ( 2012-12), p. n/a-n/a
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2012JB009538
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2012
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    detail.hit.zdb_id: 2969341-X
    detail.hit.zdb_id: 161665-1
    detail.hit.zdb_id: 3094268-8
    detail.hit.zdb_id: 710256-2
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    detail.hit.zdb_id: 2220777-6
    detail.hit.zdb_id: 3094197-0
    SSG: 16,13
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  • 10
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    Online Resource
    Constraints on North Atlantic upper mantle anisotropy from S and SS phases
    American Geophysical Union (AGU) ; 1994
    In:  Geophysical Research Letters Vol. 21, No. 4 ( 1994-02-15), p. 309-312
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 21, No. 4 ( 1994-02-15), p. 309-312
    Type of Medium: Online Resource
    ISSN: 0094-8276
    URL: Article
    DOI: 10.1029/93GL03261
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1994
    detail.hit.zdb_id: 2021599-X
    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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