Seismic anisotropy of the mantle lithosphere beneath the Swedish National Seismological Network (SNSN)

Eken, Tuna; Plomerová, Jaroslava; Roberts, Roland; Vecsey, Luděk; Babuška, Vladislav; Shomali, Hossein; Böðvarsson, Reynir

doi:10.1016/j.tecto.2009.10.012

Cited by 27 publications

(42 citation statements)

References 62 publications

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“…The fast shear wave will polarize parallel to the dominant a axis orientation distribution and hence provides an indirect indicator for mantle flow or direction of shear in the mantle. Eken et al [] show seismic anisotropy below Scandinavia from body wave analysis in the upper mantle (including the lithospheric mantle) with fast shear waves that align semiparallel with S Hmax in our study, as well as many other stress studies in Scandinavia. Depending on the coupling between crust and lithospheric mantle this could drive plate motion and generate crustal stresses.…”

Section: Discussionmentioning

confidence: 99%

Image log analysis of in situ stress orientation, breakout growth, and natural geologic structures to 2.5 km depth in central Scandinavian Caledonides: Results from the COSC‐1 borehole

et al. 2017

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Stress‐induced borehole deformation analysis in the Collisional Orogeny in the Scandinavian Caledonide deep scientific borehole establishes in situ stress orientation in a poorly characterized region in central Sweden. Two acoustic televiewer logging campaigns, with more than 1 year between campaigns, provide detailed images along the full length of the 2.5 km deep borehole for breakout, drilling‐induced tensile fracture (DITF), and natural occurring structural analysis. Borehole breakouts occur in 13 distinct zones along total length of 22 m, indicating an average maximum horizontal stress, SHmax, orientation of 127° ± 12°. Infrequent DITFs are constrained within one zone from 786 to 787 m depth (SHmax orientation: 121° ± 07°). These SHmax orientations are in agreement with the general trend in Scandinavia and are in accordance with many mechanisms that generate crustal stress (e.g., ridge push, topographic loading, and mantel driven stresses). The unique acquisition of image logs in two successions allows for analysis of time‐dependent borehole deformation, indicating that six breakout zones have crept, both along the borehole axis and radially around the borehole. Strong dynamic moduli measured on core samples and an inferred weak in situ stress anisotropy inhibit the formation of breakouts and DITFs. Natural fracture orientation below 800 m is congruent to extensional or hybrid brittle shear failure along the same trend as the current SHmax. Analysis of foliation in the image logs reinforces the interpretation that the discontinuous seismic reflectors with fluctuating dip observed in seismic profiles are due to recumbent folding and boudinage.

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Section: Discussionmentioning

confidence: 99%

Image log analysis of in situ stress orientation, breakout growth, and natural geologic structures to 2.5 km depth in central Scandinavian Caledonides: Results from the COSC‐1 borehole

et al. 2017

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“…Fouch and Rondenay (2006) made a detailed review of the methods for studying seismic anisotropy, as well as their advantages and limitations. In the past three decades, many researchers have attempted to use P-wave travel-time data to study anisotropy tomography (e.g., Babuska et al, 1984;Hearn, 1984;Hirahara and Ishikawa, 1984;Hirahara, 1988;Babuska and Cara, 1991;Mochizuki, 1995;Gresillaud and Cara, 1996;Hearn, 1996;Plomerova et al, 1996;Mochizuki, 1997;Lees and Wu, 1999;Wu and Lees, 1999;Bokelmann, 2002;Eberhart-Phillips and Henderson, 2004;Oda, 2005, 2008;Wang and Zhao, 2008;Koulakov et al, 2009;Eken et al, 2010;Plomerova et al, 2011;Tian and Zhao, 2012a;Wei et al, 2013;Koulakov et al, 2015;Menke, 2015;Wei et al, 2015). However, reliable and geologically reasonable results have been obtained only in recent years, thanks to the availability of abundant high-quality arrival-time data recorded by dense seismic arrays of permanent and portable stations at local and regional scales.…”

Section: Introductionmentioning

confidence: 99%

Seismic anisotropy tomography: New insight into subduction dynamics

2016

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Body-wave and surface-wave tomography, receiver-function imaging, and shear-wave splitting measurements have shown that seismic anisotropy and heterogeneity coexist in all parts of subduction zones, providing important constraints on the mantle flow and subduction dynamics. P-wave anisotropy tomography is a new but powerful tool for mapping three-dimensional variations of azimuthal and radial seismic anisotropy in the crust and mantle. P-wave azimuthal-anisotropy tomography has been applied widely to the Circum-Pacific subduction zones, Mainland China and North America, whereas P-wave radial-anisotropy tomography was applied to only a few areas including Northeast Japan, Southwest Japan and North China Craton. These studies have revealed complex anisotropy in the crust and mantle lithosphere associated with the surface geology and tectonics, anisotropy reflecting subduction-driven corner flow in the mantle wedge, frozen-in fossil anisotropy in the subducting slabs formed at the mid-ocean ridge, as well as olivine fabric transitions due to changes in water content, stress and temperature. Shear-wave splitting tomography methods have been also proposed, but their applications are still limited and preliminary. There is a discrepancy between the surface-wave and body-wave tomographic models in radial anisotropy of the mantle wedge beneath Japan, which is a puzzle but an intriguing topic for future studies.

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“…Previous analyses of P ‐wave traveltimes and shear‐wave splitting directionality indicate that the Precambrian mantle lithosphere of Fennoscandia can be mostly modelled by dipping foliations in the Proterozoic part and a plunging lineation in the Archean part (Plomerová et al 2001, 2006, 2008; Vecsey et al 2007; Eken et al 2010). Discrepancies between isotropic inversions of radial and tangential components (SV and SH) of direct shear waves at depths down to ∼150–200 km, which are depths corresponding to an estimate of the lithosphere–asthenosphere boundary (LAB, Plomerová et al 2008; Plomerová & Babuška 2010), have been attributed to the effect of large‐scale anisotropy in the mantle lithosphere (Eken et al 2008, 2010).…”

Section: Introductionmentioning

confidence: 99%

“…This paper aims at evaluating effects due to neglecting anisotropy in isotropic velocity images by comparing the upper mantle velocity images calculated with and without considering seismic anisotropy. For this purpose, we extract information regarding anisotropy within the upper mantle from Eken et al (2010), where we modelled fabrics of individual mantle lithosphere domains of the Baltic Shield by joint inversion of shear‐wave splitting and P ‐wave traveltime residuals evaluated from recordings of the Swedish National Seismological Network (SNSN). We apply two types of corrections for anisotropy to the traveltime residuals associated with individual rays used in the isotropic velocity tomography.…”

Section: Introductionmentioning

confidence: 99%

Effects of seismic anisotropy on P-velocity tomography of the Baltic Shield

Eken

Plomerová²,

Vecsey³

et al. 2011

Geophysical Journal International

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A B S T R A C TWe investigate possible effects of neglecting seismic anisotropy on standard isotropic Pvelocity tomographic images of the upper mantle beneath the Baltic shield. Isotropic inversions of teleseismic P-and S-wave traveltimes exhibit alternating high-and low-velocity heterogeneities down to depths of over 400 km. Differences in tomographic inversions of SV -and SH-wave traveltimes are distinct down to depths of about 200 km and are associated with anisotropy of the lithospheric mantle. Anisotropic structures of the upper mantle affect both the P and S traveltimes, shear-wave splitting as well as the P polarization directions. Joint inversion for isotropic and anisotropic velocity perturbations is not feasible due to the limited 3-D ray coverage of available data. Therefore, we correct the input traveltimes for anisotropic contributions derived from independent analyses and then perform standard isotropic inversions. These corrections are derived either directly from directional deviations of P-wave propagation or are calculated in anisotropic models retrieved by joint inversions of bodywave anisotropic parameters (P-residual spheres and shear-wave splitting). These anisotropic models are also used to fit backazimuth variations of P-wave polarization directions. General features of tomographic images calculated from the original and the anisotropy-corrected data are similar. Amplitudes of the velocity perturbations decrease below ∼200 km depth, that is in the sub-lithospheric mantle. In general, large-scale anisotropy related to the fabrics of the continental mantle lithosphere can contaminate tomographic images in some parts of models and should not be ignored.

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Seismic anisotropy of the mantle lithosphere beneath the Swedish National Seismological Network (SNSN)

Cited by 27 publications

References 62 publications

Image log analysis of in situ stress orientation, breakout growth, and natural geologic structures to 2.5 km depth in central Scandinavian Caledonides: Results from the COSC‐1 borehole

Image log analysis of in situ stress orientation, breakout growth, and natural geologic structures to 2.5 km depth in central Scandinavian Caledonides: Results from the COSC‐1 borehole

Seismic anisotropy tomography: New insight into subduction dynamics

Effects of seismic anisotropy on P-velocity tomography of the Baltic Shield

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