Azimuthal anisotropy in the lithosphere from observations of long-period S-waves

Vinnik, Lev; Kind, R.; Kosarev, G. L.; Makeyeva, Larissa

doi:10.1111/j.1365-246x.1989.tb02039.x

Cited by 118 publications

(79 citation statements)

References 7 publications

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“…The actual quantity measured on individual seismograms in the splitting intensity, S, which is defined as the amplitude of the transverse component relative to the time derivative of the radial component; this quantity can be measured either by simple projection of the components or by a singular value decomposition (SVD) procedure (Chevrot 2000). In particular, the predicted radial and transverse components for a vertically propagating shear wave that has undergone passage through a single layer of anisotropy with a horizontal axis of transversely isotropic (TI) symmetry can be written at long period (dt ( T) as (Silver and Chan 1988;Vinnik et al 1989b;Chevrot 2000):…”

Section: The Cross-correlation Methodsmentioning

confidence: 99%

“…2.1.1.3 The Multichannel (Splitting Intensity) Method The multichannel method was introduced by Chevrot (2000) (based on earlier work by Vinnik et al 1989b) as an alternative to single-record methods such as transverse component minimization and crosscorrelation. This method takes advantage of the predicted variation in the amount of energy on the uncorrected transverse component with incoming polarization angle (equivalent to the backazimuth for SKS-type phases) for a single, horizontal layer of anisotropy.…”

Section: The Cross-correlation Methodsmentioning

confidence: 99%

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Shear Wave Splitting and Mantle Anisotropy: Measurements, Interpretations, and New Directions

2009

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Measurements of the splitting or birefringence of seismic shear waves that have passed through the Earth's mantle yield constraints on the strength and geometry of elastic anisotropy in various regions, including the upper mantle, the transition zone, and the D 00 layer. In turn, information about the occurrence and character of seismic anisotropy allows us to make inferences about the style and geometry of mantle flow because anisotropy is a direct consequence of deformational processes. While shear wave splitting is an unambiguous indicator of anisotropy, the fact that it is typically a near-vertical path-integrated measurement means that splitting measurements generally lack depth resolution. Because shear wave splitting yields some of the most direct constraints we have on mantle flow, however, understanding how to make and interpret splitting measurements correctly and how to relate them properly to mantle flow is of paramount importance to the study of mantle dynamics. In this paper, we review the state of the art and recent developments in the measurement and interpretation of shear wave splitting-including new measurement methodologies and forward and inverse modeling techniques,-provide an overview of data sets from different tectonic settings, show how they help us relate mantle flow to surface tectonics, and discuss new directions that should help to advance the shear wave splitting field.

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Section: The Cross-correlation Methodsmentioning

confidence: 99%

Section: The Cross-correlation Methodsmentioning

confidence: 99%

Shear Wave Splitting and Mantle Anisotropy: Measurements, Interpretations, and New Directions

2009

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“…It provides information on the azimuthal anisotropy of the upper mantle, which is generally interpreted as due to the lattice preferred orientation (LPO) of olivine (Babuška and Cara 1991;Vinnik et al 1986;Chan 1988, 1991). The exact location of the anisotropy within the upper mantle is poorly constrained.…”

Section: Shear-wave Splitting Analysismentioning

confidence: 99%

Teleseismic studies of the lithosphere below the Abitibi-Grenville Lithoprobe transect

Rondenay¹,

Bostock²,

Hearn³

et al. 2000

Rev. Can. Sci. Terre

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Abstract:In the past decade, the Abitibi-Grenville Lithoprobe transect has been the site of numerous geological and geophysical surveys oriented towards understanding the lithospheric evolution of the southeastern Superior and adjoining Grenville provinces. Among the different geophysical methods that have been employed, earthquake seismology provides the widest range of information on the deep structures of the upper mantle. This paper presents a review of studies, both complete and ongoing, involving teleseismic datasets that were collected in 1994 and 1996 along the transect. A complete shear-wave splitting analysis has been performed on the 1994 dataset as part of a comparative study on electrical and seismic anisotropies. Results suggest a correlation between the two anisotropies (supported by xenolith data) and favour a lithospheric origin for the seismic anisotropy. The two anisotropies are believed to represent the fossilized remnants of Archean strain fields in the lithospheric roots of the Canadian Shield. Preliminary splitting results for the 1996 experiment suggest that the S-wave azimuthal anisotropy may be depth dependent and laterally varying. Ongoing receiver function analysis and traveltime inversion studies provide velocity models of the crust and upper mantle beneath the study area. Preliminary receiver function results reveal the presence of an S-velocity increase at -90-100 km depth which appears to be laterally continuous over 200 km. Traveltime inversion models indicate the presence of an elongate, low-velocity anomaly beneath the southern portion of the 1996 array which strikes obliquely to major geological structures at the surface (e.g., Grenville Front). Preliminary interpretation relates this anomaly to the same process (e.g., fixed mantle plume, continental rifting) responsible for the emplacement of the Monteregian Hills igneous province.Résumé : Au cours de la dernière décennie, de nombreuses campagnes géologiques et géophysiques ont été effectuées le long de la traverse Abitibi-Grenville du projet Lithoprobe, dans le but de comprendre l'évolution lithosphérique de la partie sud-est de la Province du Supérieur et de la Province de Grenville. Parmi les différentes méthodes géophysiques employées, la sismologie passive est sans doute celle qui procure le plus d'informations sur les structures profondes du manteau supérieur. Cet article passe en revue les études, complétées et en cours, s'appuyant sur les données télésismi-ques enregistrées en 1994 et en 1996, le long de la traverse. Une analyse complète de biréfringence des ondes S a été effectuée sur les données de 1994, dans le cadre d'une étude comparative entre l'anisotropie électrique et sismique. Les résultats obtenus suggèrent une corrélation entre les deux anisotropies (observation supportée par l'analyse de xénoli-thes), et favorisent une anisotropie sismique d'origine lithosphérique. Les deux anisotropies semblent associées à des champs de déformation archéens fossilisés dans les racines lithosphériques du Bouclier canadien...

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“…The large wavelengths used in longperiod surface waves studies means that such methods are insensitive to heterogeneity less than the wavelength of about 1500 km. More recently in an effort to address the problem of regional variations of anisotropy the splitting of SKS teleseismic shear waves which propagate vertically have been extensively used (Kind et al, 1985, Silver and Chan 1988Vinnik et al, 1989). At continental stations, SKS studies show that the azimuth of the fast polarization direction is frequently parallel to the trend of mountain belts (see reviews from Silver, 1996 andSavage, 1999).…”

Section: Introductionmentioning

confidence: 99%

The Seismic anisotropy of the Earth's mantle: From single crystal to polycrystal

Mainprice¹,

Barruol²,

Ismaı̈l³

2000

Earth's Deep Interior: Mineral Physics and Tomography From the Atomic to the Global Scale

220

172

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The anisotropic single crystal seismic properties are reviewed in the light of recent experimental and theoretical determinations. Although considerable progress has been made on the determination of single crystal properties, data are still lacking, particularly for the temperature derivatives of transition zone and lower mantle phases. The common types of LPO of olivine, opx and cpx are presented together with their associated seismic properties. It is emphasized that simple seismic symmetry pattern of upper mantle rocks are a direct result of the interaction of olivine, opx and cpx. Using the standard structural frame (X lineation, Z pole to foliation) for typical LPOs of olivine, opx and cpx have the maximum Vp parallel to X, in the XZ plane and parallel to Y respectively. Destructive interference occurs between these minerals and hence P-wave anisotropy should be sensitive to the aggregate composition. For shear wave splitting (dVs) typical olivine and opx LPOs result in similar patterns with the maximum dVs in the YZ plane and the fast split shear wave (Vs1) polarized parallel to the foliation. A typical cpx LPO on the other hand produces destructive interference as the max dVs is close to X. By comparison with experiments and numerical simulations, it is estimated that upper mantle samples have an olivine LPO strength which recorded shear strain gamma of between 0.25 and 2.0. Pyrolite and piclogite models are compared with global transverse isotropic models. The slowly reducing P-wave anisotropy in the first 200 km can be explained by a model with constant composition and LPO strength. The sharp decrease in the observed anisotropy in the global models cannot be explained by the transformation of opx to cpx at 300 km, it is proposed that this decrease is due to a reduction in LPO strength from 200 to 350 km at the base of the lithosphere.

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Azimuthal anisotropy in the lithosphere from observations of long-period S-waves

Cited by 118 publications

References 7 publications

Shear Wave Splitting and Mantle Anisotropy: Measurements, Interpretations, and New Directions

Shear Wave Splitting and Mantle Anisotropy: Measurements, Interpretations, and New Directions

Teleseismic studies of the lithosphere below the Abitibi-Grenville Lithoprobe transect

The Seismic anisotropy of the Earth's mantle: From single crystal to polycrystal

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