Waveform inversion using secondary observables

Cara, Michel; Lévêque, Jean Jacques

doi:10.1029/gl014i010p01046

Cited by 130 publications

(118 citation statements)

References 6 publications

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“…However, each path has a path-specific crustal model determined by averaging the crustal part of 3SMAC along the path. Cara and Lévêque (1987) show that for their technique, the final velocity structure is weakly dependent on the reference model. In addition, at 50 s period the maximum sensitivity of even the fundamental mode is located below the crust, so that our dataset is primarily sensitive to upper mantle structure.…”

Section: Seismic Constraints On the Upper Mantle Beneath Southern Africamentioning

confidence: 99%

“…We first use the automated version (Debayle, 1999) of the Cara and Lévêque (1987) waveform inversion technique to determine a onedimensional (1D) path average upper mantle velocity model compatible with an observed surface wave seismogram. We then combine the 1D velocity models in a tomographic inversion using the continuous regionalization algorithm of Montagner (1986) as modified by Debayle and Sambridge (2004) to obtain at each depth (50 to 400 km in steps of 25 km) the local Sv-wave speed (see Debayle and Kennett (2000a) for details).…”

Section: Seismic Constraints On the Upper Mantle Beneath Southern Africamentioning

confidence: 99%

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The state of the upper mantle beneath southern Africa

2006

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Section: Seismic Constraints On the Upper Mantle Beneath Southern Africamentioning

confidence: 99%

Section: Seismic Constraints On the Upper Mantle Beneath Southern Africamentioning

confidence: 99%

The state of the upper mantle beneath southern Africa

2006

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“…Including overtones in the tomography not only constrains deeper structure better than does the fundamental mode, the overtones improve resolution at shallower depths. An advantage in using the Debayle & Ricard (2012) implementation of the Cara & Lévêque (1987) method over other automated waveform inversion procedures is that it does not require separating the fundamental mode and overtones into unique time windows before making the wave speed measurements since the observed seismogram is modelled as a sum of interfering modes.…”

Section: Extracting Structure Of the Upper Mantlementioning

confidence: 99%

“…Extracting the secondary observables (Cara & Lévêque 1987) and inverting them for the path average velocity structure follows closely the method employed by Debayle & Ricard (2012) but adapted to transverse component seismograms. The secondary observables are measured using cross-correlation.…”

Section: Extracting and Fitting The Secondary Observablesmentioning

confidence: 99%

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A global horizontal shear velocity model of the upper mantle from multimode Love wave measurements

Ho¹,

Priestley²,

Debayle

2016

Geophys. J. Int.

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S U M M A R YSurface wave studies in the 1960s provided the first indication that the upper mantle was radially anisotropic. Resolving the anisotropic structure is important because it may yield information on deformation and flow patterns in the upper mantle. The existing radially anisotropic models are in poor agreement. Rayleigh waves have been studied extensively and recent models show general agreement. Less work has focused on Love waves and the models that do exist are less well-constrained than are Rayleigh wave models, suggesting it is the Love wave models that are responsible for the poor agreement in the radially anisotropic structure of the upper mantle. We have adapted the waveform inversion procedure of Debayle & Ricard to extract propagation information for the fundamental mode and up to the fifth overtone from Love waveforms in the 50-250 s period range. We have tomographically inverted these results for a mantle horizontal shear wave-speed model (β h (z)) to transition zone depths. We include azimuthal anisotropy (2θ and 4θ terms) in the tomography, but in this paper we discuss only the isotropic β h (z) structure. The data set is significantly larger, almost 500 000 Love waveforms, than previously published Love wave data sets and provides ∼17 000 000 constraints on the upper-mantle β h (z) structure. Sensitivity and resolution tests show that the horizontal resolution of the model is on the order of 800-1000 km to transition zone depths. The high wave-speed roots beneath the oldest parts of the continents appear to extend deeper for β h (z) than for β v (z) as in previous β h (z) models, but the resolution tests indicate that at least parts of these features could be artefacts. The low wave speeds beneath the mid-ocean ridges fade by ∼150 km depth except for the upper mantle beneath the East Pacific Rise which remains slow to ∼250 km depth. The resolution tests suggest that the low wave speeds at deeper depths beneath the East Pacific Rise are not solely due to vertical smearing of shallow, low wave speeds. Four prominent, low wave-speed features occur at transition zone depths-one aligned along the East African Rift, one centred south of the Indian peninsula, one located south of New Zealand and one in the south Pacific Ocean coinciding with the location of the South Pacific Superswell. The low wave-speed features south of New Zealand and south of the Indian peninsula correspond spatially with the two largest negative geoid lows on Earth.

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Rayleigh wave phase velocity and error maps up to the fifth overtone

Durand

Debayle

Ricard

2015

Geophysical Research Letters

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We present a global data set of phase velocity maps for Rayleigh waves, with their errors. These maps are obtained from the tomographic inversion of phase velocity curves measured in the period range 40–250 s by Debayle and Ricard (2012), completed with new measurements at longer periods, between 150 and 360 s. The full data set includes ∼22,000,000 phase velocity measurements combined to build 60 phase velocity maps covering the period range 40–360 s for the fundamental mode and up to the fifth overtone. Each phase velocity map is provided with its a posteriori error, resulting in a unique data set which can be combined with other seismic measurements (surface waves, normal modes, and body waves) in regional and global tomographic studies. A preliminary inversion of this data set shows that it provides constraints on the shear velocity structure down to 1000 km depth.

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Waveform inversion using secondary observables

Cited by 130 publications

References 6 publications

The state of the upper mantle beneath southern Africa

The state of the upper mantle beneath southern Africa

A global horizontal shear velocity model of the upper mantle from multimode Love wave measurements

Rayleigh wave phase velocity and error maps up to the fifth overtone

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