Shear wave splitting in the mantle <i>Ps</i> phases

Vinnik, Lev; Montagner, Jean‐Paul

doi:10.1029/96gl02263

Cited by 71 publications

(57 citation statements)

References 8 publications

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“…The presence of dipping interfaces or anisotropy always complicates the interpretation of receiver functions [Cassidy, 1992;Vinnik and Montagner, 1996]; by removing the differences in receiver functions caused by variations in incidence angle, we have made it easier to identify other differences that reflect dipping or anisotropic structure. structure, we will defer examination of the tangential receiver functions to a later work (C. H. Jones et al, manuscript in preparation, 1998).…”

Section: Comparing and Compositing Receiver Functionsmentioning

confidence: 99%

Seismic structure of the lithosphere from teleseismic converted arrivals observed at small arrays in the southern Sierra Nevada and vicinity, California

Jones¹,

Phinney²

1998

J. Geophys. Res.

124

135

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Abstract. 21 well-distributed teleseisms (30 ø to 100 ø distance) were recorded by mixed broadband (BB) and short-period (SP) seismic arrays at Mineral King (MK) and Horseshoe Meadow (HM) in the southern Sierra Nevada and at Darwin Plateau (DP) between the Inyo and Argus ranges. These arrays permit identification and separation of direct P and S arrivals, reflections from topography, scattered energy, and arrivals from different back azimuths (multipath arrivals). P-to-S conversions can be identified from beamed BB or SP seismograms. Least squares time domain processing recovered single-event receiver functions from these beamed seismograms. Converted phases attributable to the Moho are clear and uncomplicated at DP; Ps-P times of 3.9-4.2 s correspond to crustal thicknesses of 31-33 km, assuming a mean P crustal velocity of 6.2 km/s and a Poisson's ratio (v) of 0.255. Ps-P times at HM (eastern Sierra) are 3.9-4.6 s (32-37 km) excepting some unusual seismograms from events at back azimuths of 2250-239 ø. MK (western Sierra) times for Ps-P show a strong E-W asymmetry: 3.9-4.1 s (31-33 kin) from the east, and 4.8-5.3 s (39-42 km) from the west. The MK arrivals from the east are multiple and substantially weaker by comparison with HM and DP. These results confirm the absence of a thick crust under the southern High Sierra inferred from both a refraction experiment coincident with this experiment and some earlier studies. At DP the Moho event follows an intracrustal negative polarity event defining the top of an S wave low-velocity zone. This feature dips west under the Sierran crest at HM but is absent farther west at MK. This feature appears to be a manifestation of extensional strain and thus indicates that the surficially undeformed Sierra overlies a tectonized lower crust. Sub-Moho energy is absent under the Basin and Range (DP) but is conspicuous under the High Sierra at positive arrivals -7.3 s (MK) and -9 s (HM) after the P. These arrivals might be from the base of a low-velocity, low-density upper mantle body supporting the Sierra.

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Section: Comparing and Compositing Receiver Functionsmentioning

confidence: 99%

Seismic structure of the lithosphere from teleseismic converted arrivals observed at small arrays in the southern Sierra Nevada and vicinity, California

Jones¹,

Phinney²

1998

J. Geophys. Res.

124

135

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“…The wadsleyite to ringwoodite transformation results in the lowering of anisotropy with depth (see Table 1) in the lower part of the transition zone, whereas the exsolution of Ca-perovskite from majorite garnet would result in an increase. Recent seismic studies by Vinnik and co-workers (Vinnik and Montagner, 1996;Vinnik et al, 1997) show evidence for a weakly anisotropic (1.5%) layer for S-waves at the bottom 40 km of the transition zone (620-660 km). The global tomography models (e.g.…”

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

218

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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“…Thus, although great heterogeneity of anisotropy with depth has been suggested, this heterogeneity remains to be demonstrated conclusively. Efforts to constrain the anisotropic region using seismological methods have been made by many researchers (e.g., Herquel et al, 1995;Vinnik and Montagner, 1996). Vinnik and Montagner (1996) used weak P-to-S converted waves from stacked seismograms to determine anisotropy in the mantle transition zone.…”

Section: Introductionmentioning

confidence: 99%

“…Efforts to constrain the anisotropic region using seismological methods have been made by many researchers (e.g., Herquel et al, 1995;Vinnik and Montagner, 1996). Vinnik and Montagner (1996) used weak P-to-S converted waves from stacked seismograms to determine anisotropy in the mantle transition zone. Iidaka and Niu (1998) and lower mantle anisotropy by comparing waveform of SKS and P660s.…”

Section: Introductionmentioning

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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Shear wave splitting in the mantle Ps phases

Cited by 71 publications

References 8 publications

Seismic structure of the lithosphere from teleseismic converted arrivals observed at small arrays in the southern Sierra Nevada and vicinity, California

Seismic structure of the lithosphere from teleseismic converted arrivals observed at small arrays in the southern Sierra Nevada and vicinity, California

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

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

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