On Presence of Seismic Anisotropy in the Asthenosphere beneath Continents and its Dependence on Plate Velocity: Significance of Reference Frame Selection

Kubo, Atsuki; Hiramatsu, Yoshihiro

doi:10.1007/s000240050115

Cited by 12 publications

(9 citation statements)

References 36 publications

(67 reference statements)

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“…For the first correction, we estimate SKS splitting parameters, the direction of the fast-polarized wave and the delay time between the fast and slow polarized waves [Silver and Chan, 1991]. The estimated SKS splitting parameters are consistent with those reported by Kubo and Hiramatsu [1998] and independent of source locations, indicating little effect of the upper mantle anisotropy of source-side in the following analysis. The corrected travel times are about one second for each event.…”

Section: Datasupporting

confidence: 79%

“…[6] We apply two corrections to the observed waveforms before the analysis of S, ScS and SKS waves, removing the effects of the upper mantle anisotropy beneath the station [Kubo and Hiramatsu, 1998] and the heterogeneity of the shear wave velocity in the upper-and mid-mantle. For the first correction, we estimate SKS splitting parameters, the direction of the fast-polarized wave and the delay time between the fast and slow polarized waves [Silver and Chan, 1991].…”

Section: Datamentioning

confidence: 99%

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Thick and anisotropic D″ layer beneath Antarctic Ocean

Usui

Hiramatsu

Furumoto

et al. 2005

Geophysical Research Letters

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Waveform modeling and travel times analyses of S, ScS and SKS phases recorded at the broad‐band permanent station SYO in the Antarctic are used to determine the shear wave velocity structure and transverse isotropy in the D″ layer beneath the Antarctic Ocean. The SH wave structure has a discontinuity with the velocity increase of 2.0% at 2550 km. The SV structure is similar to PREM model. The magnitude of the anisotropy is highest at the top of D″ layer and lowest at the core‐mantle boundary. The D″ layer beneath the Antarctic Ocean is significantly thicker than those beneath Alaska and the Caribbean Sea. We attribute this anisotropic D″ layer to paleo‐slab materials. The subduction in and around the Antarctic Ocean has started ∼180 Ma and is the one of the oldest in the world. It has provided a large amount of the slab materials in the lowermost mantle.

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Section: Datasupporting

confidence: 79%

Section: Datamentioning

confidence: 99%

Thick and anisotropic D″ layer beneath Antarctic Ocean

Usui

Hiramatsu

Furumoto

et al. 2005

Geophysical Research Letters

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“…Mantle anisotropy observed in most regions can be explained by an alignment of olivine due to mantle flow. Kubo and Hiramatsu (1998) calculated the absolute plate velocity direction at seismic stations in China based on the AM1-2 model (Minster and Jordan, 1978) and the HS2-NUVEL1 model (Gripp and Gordon, 1990) (Figs. 5 and 6).…”

Section: Resultsmentioning

confidence: 99%

Mantle and crust anisotropy in the eastern China region inferred from waveform splitting of SKS and PpSms

Iidaka

Niu

2014

Earth Planet Sp

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S-waves converted from P-wave at different boundaries inside the earth, i.e., the Moho discontinuity and CMB, are used to determine the distribution of anisotropy in different layers. A clear later phase at approximately 17 sec after the direct P-wave, which is identified to be PpSms (a phase that is P-to-S converted at the free surface and is reflected by the Moho discontinuity on the receiver side), is observed in the radial component of seismograms recorded by broadband stations in the east China region. Waveform splitting observed from the PpSms and SKS suggests that the crust beneath the eastmost part of China is almost isotropic, and the mantle is weakly anisotropic. Splitting analysis using converted waves is a promising technique for investigating the depth distribution of shear-wave splitting.

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“…Although APM estimates are key to linking deep Earth processes with tectonics and surface motions, APM is still poorly known and current models vary significantly among each other. Consequently, our understanding of a given geodynamic process depends on the choice of APM model [e.g., Kubo and Hiramatsu , 1998; Barruol and Hoffmann , 1999; Simons and van der Hilst , 2003; Becker et al , 2007; Funiciello et al , 2008]. As a result of the diversity in APM models, recent studies have started to “rank” published APM models by their ability to explain a set of observations or a chosen geodynamical model [e.g., Lallemand et al , 2008; Schellart et al , 2008; Long and Silver , 2009].…”

Section: Introductionmentioning

confidence: 99%

Absolute plate motions constrained by shear wave splitting orientations with implications for hot spot motions and mantle flow

Kreemer

2009

J. Geophys. Res.

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[1] Here, I present a new absolute plate motion model of the Earth's surface, determined from the alignment of present-day surface motions with 474 published shear wave (i.e., SKS) splitting orientations. When limited to oceanic islands and cratons, splitting orientations are assumed to reflect anisotropy in the asthenosphere caused by the differential motion between lithosphere and mesosphere. The best fit model predicts a 0.2065°/Ma counterclockwise net rotation of the lithosphere as a whole, which revolves around a pole at 57.6°S and 63.2°E. This net rotation is particularly well constrained by data on cratons and/or in the Indo-Atlantic region. The average data misfit is 19°and 24°for oceanic and cratonic areas, respectively, but the normalized root-mean-square misfits are about equal at 5.4 and 5.2. Predicted plate motions are very consistent with recent hot spot track azimuths (<8°on many plates), except for the slowest moving plates (Antarctica, Africa, and Eurasia). The difference in hot spot propagation vectors and plate velocities describes the motion of hot spots (i.e., their underlying plumes). For most hot spots that move significantly, the motions are considerably smaller than and antiparallel to the absolute plate velocity. Only when the origin depth of the plume is considered can the hot spot motions be explained in terms of mantle flow. The results are largely consistent with independent evidence of subasthenospheric mantle flow and asthenospheric return flow near spreading ridges. The results suggest that, at least where hot spots are, the lithosphere is decoupled from the mesosphere, including in western North America.

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On Presence of Seismic Anisotropy in the Asthenosphere beneath Continents and its Dependence on Plate Velocity: Significance of Reference Frame Selection

Cited by 12 publications

References 36 publications

Thick and anisotropic D″ layer beneath Antarctic Ocean

Thick and anisotropic D″ layer beneath Antarctic Ocean

Mantle and crust anisotropy in the eastern China region inferred from waveform splitting of SKS and PpSms

Absolute plate motions constrained by shear wave splitting orientations with implications for hot spot motions and mantle flow

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