Measuring surface-wave overtone phase velocities using a mode-branch stripping technique

Heijst, H. J. van; Woodhouse, John

doi:10.1111/j.1365-246x.1997.tb01217.x

Cited by 86 publications

(78 citation statements)

References 36 publications

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“…Ekström et al (1997) mapped phase velocity by minimizing dispersion residuals of fundamental Love and Rayleigh waveforms, isolated from interfering overtones via phase-matched filters. Van Heijst and Woodhouse (1999) measured global high-resolution phase velocity distributions of fundamental-mode and overtone SWs via a mode-branch stripping technique (van Heijst and Woodhouse, 1997). Trampert and Woodhouse (2003) used fundamental-mode SWs to map anisotropic phase velocities.…”

Section: Surface Waves: Applicationsmentioning

confidence: 99%

Multiscale adjoint waveform tomography for surface and body waves

2015

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International audienceWe have developed a wavelet-multiscale adjoint scheme for the elastic full-waveform inversion of seismic data, including body waves (BWs) and surface waves (SWs). We start the inversion on the SW portion of the seismograms. To avoid cycle skipping and reduce the dependence on the initial model of these dispersive waves, we commence by minimizing an envelope-based misfit function. Subsequently, we proceed to the minimization of a waveform-difference (WD) metric applied to the SWs only. After that, we fit BWs and SWs indiscriminately using a WD misfit metric. In each of these three steps, we guide the iterative inversion through a sequence of nested subspace projections in a wavelet basis. SW analysis preserves a wealth of near-surface features that would be lost in conventional BW tomography. We used a toy model to illustrate the dispersive and cycle-skipping behavior of the SWs, and to introduce the two ways by which we combat the nonlinearity of waveform inversions involving SWs. The first is the wavelet-based multiscale character of the method, and the second the envelope-based misfit function. Next, we used an industry synthetic model to perform realistic numerical experiments to further develop a strategy for SW and joint SW as well as BW tomography. The effect of incorrect density information on wave-speed inversions was also evaluated. We ultimately formalize a flexible scheme for full-waveform inversion based on adjoint methods that includes BWs and SWs, and also considers P- and S-wave speeds, as well as density. Our method is applicable to waveform inversion in exploration geophysics, geotechnical engineering, regional, and global seismology.Read More: http://library.seg.org/doi/10.1190/geo2014-0461.

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Section: Surface Waves: Applicationsmentioning

confidence: 99%

Multiscale adjoint waveform tomography for surface and body waves

2015

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“…Love and Rayleigh wave dispersion maps for the fundamental mode exist (e.g. Trampert & Woodhouse 1995Larson & Ekström 2001;Visser et al 2007;Ekström 2011;Pasyanos et al 2014) and Rayleigh wave maps exist for some higher modes (van Heijst & Woodhouse 1997, 1999Shapiro & Ritzwoller 2002;Beucler et al 2003;Visser et al 2007Visser et al , 2008. Less work has been done on inverting Love wave measurements for β h (z) models (Li & Romanowciz 1996;Mégnin & Romanowicz 2000;Zhou et al 2005) and most existing β h (z) upper-mantle models are constrained using only fundamental mode measurements.…”

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confidence: 99%

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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“…The idea of the reliability for waveform fitting is modelled on the early works for multimode dispersion measurements for a source-receiver paths by van Heijst & Woodhouse (1997) and its modified versions by Yoshizawa & Kennett (2002) and Yoshizawa & Ekström (2010). Here, we briefly summarize the idea of how to quantify the goodness of the waveform fit and to estimate the frequency-dependent reliability of dispersion measurements.…”

Section: Reliability Of Dispersion Measurementsmentioning

confidence: 99%

Interstation phase speed and amplitude measurements of surface waves with nonlinear waveform fitting: application to USArray

Hamada

Yoshizawa

2015

Geophys. J. Int.

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S U M M A R YA new method of fully nonlinear waveform fitting to measure interstation phase speeds and amplitude ratios is developed and applied to USArray. The Neighbourhood Algorithm is used as a global optimizer, which efficiently searches for model parameters that fit two observed waveforms on a common great-circle path by modulating the phase and amplitude terms of the fundamental-mode surface waves. We introduce the reliability parameter that represents how well the waveforms at two stations can be fitted in a time-frequency domain, which is used as a data selection criterion. The method is applied to observed waveforms of USArray for seismic events in the period from 2007 to 2010 with moment magnitude greater than 6.0. We collect a large number of phase speed data (about 75 000 for Rayleigh and 20 000 for Love) and amplitude ratio data (about 15 000 for Rayleigh waves) in a period range from 30 to 130 s. The majority of the interstation distances of measured dispersion data is less than 1000 km, which is much shorter than the typical average path-length of the conventional single-station measurements for source-receiver pairs. The phase speed models for Rayleigh and Love waves show good correlations on large scales with the recent tomographic maps derived from different approaches for phase speed mapping; for example, significant slow anomalies in volcanic regions in the western Unites States and fast anomalies in the cratonic region. Local-scale phase speed anomalies corresponding to the major tectonic features in the western United States, such as Snake River Plains, Basin and Range, Colorado Plateau and Rio Grande Rift have also been identified clearly in the phase speed models. The shortpath information derived from our interstation measurements helps to increase the achievable horizontal resolution. We have also performed joint inversions for phase speed maps using the measured phase and amplitude ratio data of vertical component Rayleigh waves. These maps exhibit better recovery of phase speed perturbations, particularly where the strong lateral velocity gradient exists in which the effects of elastic focussing can be significant; that is, the Yellowstone hotspot, Snake River Plains, and Rio Grande Rift. The enhanced resolution of the phase speed models derived from the interstation phase and amplitude measurements will be of use for the better seismological constraint on the lithospheric structure, in combination with dense broad-band seismic arrays.

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Measuring surface-wave overtone phase velocities using a mode-branch stripping technique

Cited by 86 publications

References 36 publications

Multiscale adjoint waveform tomography for surface and body waves

Multiscale adjoint waveform tomography for surface and body waves

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

Interstation phase speed and amplitude measurements of surface waves with nonlinear waveform fitting: application to USArray

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