Upper mantle anisotropy in the New Zealand Region

Klosko, Eryn; Wu, Francis T.; Anderson, Helén; Eberhart‐Phillips, Donna; McEvilly, T. V.; Audoine, Etienne; Savage, M. K.; Gledhill, Ken

doi:10.1029/1999gl900273

Cited by 80 publications

(106 citation statements)

References 20 publications

(17 reference statements)

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“…They applied this approach to the Marlborough region in central New Zealand, and their results show variations in P-wave anisotropy in the brittle upper crust, ductile lower crust, mantle wedge and the subducting Pacific slab. The patterns are consistent with the SWS observations (Klosko et al, 1999;Audoine et al, 2000Audoine et al, , 2004, but show some additional features. The maximum anisotropy is approximately 12% oriented northeast, between the Awatere and Wairau faults.…”

Section: New Zealandsupporting

confidence: 88%

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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Section: New Zealandsupporting

confidence: 88%

Seismic anisotropy tomography: New insight into subduction dynamics

2016

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“…A range of 033 ~ to 039 ~ is calculated for the azimuth long axis of the finite strain ellipse in the upper mantle (Table 3). The azimuth of the fast direction shear-wave splitting data (Klosko et al 1999;Audoine et al 2000) is 046 ~ • 7 ~ These shear-wave splitting data are consistent with, but slightly clockwise of, the azimuths predicted by the model (Fig. 11).…”

Section: Marlborough Fault System South Island New Zealandsupporting

confidence: 83%

“…In general, shear-wave splitting is observed over a large area, up to several hundred kilometres perpendicular to the strike of the plate boundary (e.g. Ozalaybey & Savage 1995;Klosko et al 1999;Audoine et al 2000;Polet & Kanamori 2002). Thus, the width of the deformed zone in the mantle is consistent with the mantle controlling large-scale crustal block rotations.…”

Section: Distributed Mantle Deformation In Obliquely Convergent Envirmentioning

confidence: 90%

“…Therefore, to compare the sidedriven model quantitatively relative to the bottom-driven model, our calculations assume a (1987); shear-wave splitting data from Ozalaybey & Savage (1995) consistent with Polet & Kanamori (2002). + Palaeomagnetlc data from Roberts (1992) and Little & Roberts (1997); shear-wave splitting data from Audoine et al (2000) consistent with Klosko et al (1999). circular crustal block (Fig.…”

Section: Eastern Transverse Ranges Southern Californiamentioning

confidence: 99%

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Vertical-axis rotation of rigid crustal blocks driven by mantle flow

Giorgis

Markley

Tikoff

2004

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Vertical-axis rotation of rigid crustal blocks occurs in a variety of obliquely convergent and divergent plate boundaries. We quantify the rotation of these blocks using models of transpressional and transtensional kinematics, and corroborate our results using physical models where rigid blocks rotate in response to flow of a ductile substrate. Consequently, one can explicitly demonstrate a relationship between the amount of rotation of a rigid crustal block and strain recorded in ductile substrate. This strain should be reflected directly by the orientation of rock fabrics, such as those measured by shear-wave splitting in the in situ upper mantle.sWe apply this approach to southern California and New Zealand by using previously documented palaeomagnetic rotations and plate motion vectors, and calculate the strain recorded by the material below rigid blocks. These strain calculations are compared to shear-wave splitting data, which record upper mantle fabric, from the same region. Our model results suggest that similar deformation is recorded by the upper crust and lithospheric mantle. A bottom-driven flow, in which mantle deformation drives upper crustal rotations, is most consistent with these observations.

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“…In addition, even if a good fit to the data can be achieved, the resulting model will not be correct since it is underparameterized. Passive teleseismic experiments often observe significant shear wave splitting (e.g., 2.2 s beneath South Island, New Zealand [Klosko et al, 1999]). Shear wave splitting measurements are usually attributed to anisotropy in the mantle .…”

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confidence: 99%

Anisotropy of schists: Contribution of crustal anisotropy to active source seismic experiments and shear wave splitting observations

Godfrey¹,

Christensen²,

Okaya³

2000

J. Geophys. Res.

147

175

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Abstract. We have made sets of five independent compressional and shear wave velocity measurements, which with density, allow us to completely characterize the transverse isotropy of samples from five metamorphic belts: the Haast schist terrane (South Island, New Zealand), Poultney slate, Chugach phyllite, Coldfoot schist, and Pelona schist (United States). These velocity measurements include compressional wave velocities for propagation parallel, perpendicular, and at 45 ø to the symmetry axis, shear wave velocity for propagation and particle motion perpendicular to the symmetry axis, and shear wave velocity for propagation parallel to the symmetry axis. Velocity measurements were made up to pressures of 1 GPa (-35-km depth) where microcracks are closed and anisotropy is due to preferred mineral orientation. Our samples exhibit compressional wave anisotropy of 9-20% as well as significant shear wave splitting. Metamorphic terranes that are anisotropic to ultrasonic waves may also be anisotropic at the scale of active and passive seismic experiments. Our data suggest that a significant thickness (10-20 km) of appropriately oriented (steeply dipping foliation) schist in the crust could contribute as much as 45% of observed shear wave splitting. Our data set can also be used to model the effects of crustal anisotropy for active source seismic experiments in order to determine if the anisotropy of the terrane is significant and needs to be taken into account during processing and modeling of the data.

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Upper mantle anisotropy in the New Zealand Region

Cited by 80 publications

References 20 publications

Seismic anisotropy tomography: New insight into subduction dynamics

Seismic anisotropy tomography: New insight into subduction dynamics

Vertical-axis rotation of rigid crustal blocks driven by mantle flow

Anisotropy of schists: Contribution of crustal anisotropy to active source seismic experiments and shear wave splitting observations

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