Theoretical background for continental- and global-scale full-waveform inversion in the time-frequency domain

Fichtner, Andreas; Kennett, B. L. N.; Igel, Heiner; Bunge, Hans‐Peter

doi:10.1111/j.1365-246x.2008.03923.x

Cited by 249 publications

(190 citation statements)

References 78 publications

(133 reference statements)

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“…Unlike other spectral element models which use a full 3-D numerical calculation for the synthetic seismogram and Fréchet kernels (e.g. Fichtner et al 2008;Bozdaĝ et al 2011;Colli et al 2013), SEMum2 uses a spectral element method to calculate synthetic seismograms and NACT to calculate the sensitivity kernels, making it faster than conventional full waveform inversion techniques. Short period group velocity dispersion maps are included to constrain the crustal structure.…”

Section: O R R E L At I O N W I T H O T H E R β β H (Z) M O D E L Smentioning

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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Section: O R R E L At I O N W I T H O T H E R β β H (Z) M O D E L Smentioning

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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“…Similar quantifiers of waveform differences are frequently used in full-waveform inversion (e.g. Fichtner et al, 2008;van Leeuwen and Mulder, 2010;Bozdag et al, 2011;Rickers et al, 2012Rickers et al, , 2013. Since density impacts P and S energies in the same way, there is no need for any component rotation.…”

Section: Quantification Of Waveform Differencesmentioning

confidence: 99%

The imprint of crustal density heterogeneities on regional seismic wave propagation

2016

Self Cite

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Abstract. Density heterogeneities are the source of mass transport in the Earth. However, the 3-D density structure remains poorly constrained because travel times of seismic waves are only weakly sensitive to density. Inspired by recent developments in seismic waveform tomography, we investigate whether the visibility of 3-D density heterogeneities may be improved by inverting not only travel times of specific seismic phases but complete seismograms.As a first step in this direction, we perform numerical experiments to estimate the effect of 3-D crustal density heterogeneities on regional seismic wave propagation. While a finite number of numerical experiments may not capture the full range of possible scenarios, our results still indicate that realistic crustal density variations may lead to travel-time shifts of up to ∼ 1 s and amplitude variations of several tens of percent over propagation distances of ∼ 1000 km. Both amplitude and travel-time variations increase with increasing epicentral distance and increasing medium complexity, i.e. decreasing correlation length of the heterogeneities. They are practically negligible when the correlation length of the heterogeneities is much larger than the wavelength. However, when the correlation length approaches the wavelength, density-induced waveform perturbations become prominent. Recent regional-scale full-waveform inversions that resolve structure at the scale of a wavelength already reach this regime.Our numerical experiments suggest that waveform perturbations induced by realistic crustal density variations can be observed in high-quality regional seismic data. While density-induced travel-time differences will often be small, amplitude variations exceeding ±10 % are comparable to those induced by 3-D velocity structure and attenuation.While these results certainly encourage more research on the development of 3-D density tomography, they also suggest that current full-waveform inversions that use amplitude information may be biased due to the neglect of 3-D variations in density.

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“…Separating instantaneous amplitude and phase information of the seismogram is beneficial to the convergence properties of FWI (Fichtner, 2011;Bozdag et al, 2011;Fichtner et al, 2008). The modified instantaneous phase is less liable to cycle skipping when FWI is applied to limitedoffset, band-limited seismic reflection data (Jimenez-Tejero et al, 2015), which is commonly the case in near-surface marine reflection seismic; furthermore, the phase-only virtual source for Pwave velocity is naturally uncoupled in the reflection regime with Poisson's ratio and density over the whole offset range, for it is less AVO-dependent.…”

Section: Complex Trace Inversion To Improve the Model Kinematicsmentioning

confidence: 99%

Pre-stack full waveform inversion of ultra-high-frequency marine seismic reflection data

Provenzano

Vardy

Henstock

2017

Geophysical Journal International

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SUMMARYThe full waveform inversion (FWI) of seismic reflection data aims to reconstruct a detailed physical properties model of the subsurface, fitting both the amplitude and traveltime of the reflections generated at physical discontinuities in the propagation medium. Unlike reservoirscale seismic exploration, where seismic inversion is a widely adopted remote characterisation tool, ultra high frequency (UHF, 0.2-4.0 kHz) multi-channel marine reflection seismology is still most often limited to a qualitative interpretation of the reflections' architecture. Here we propose an elastic full waveform inversion methodology, custom-tailored for pre-stack UHF marine data in vertically heterogeneous media to obtain a decimetric-scale distribution of Pimpedance, density and Poisson's ratio within the shallow sub-seabed sediments. We address the deterministic multi-parameter inversion in a sequential fashion. The complex trace instantaneous phase is first inverted for the P-wave velocity to make-up for the lack of low-frequency in the data and reduce the non-linearity of the problem. This is followed by a short-offset Pimpedance optimisation and a further step of full offset range Poisson's ratio inversion. Provided that the seismogram contains wide reflection angles (> 40 degrees), we show that it is possible to invert for density and decompose a-posteriori the relative contribution of P-wave velocity and density to the P-impedance. A broad range of synthetic tests is used to prove the potential of the methodology and highlights sensitivity issues specific to UHF seismic. An example application to real data is also presented. In the real case, trace normalisation is applied to minimise the systematic error deriving from an inaccurate source wavelet estimation. G. Provenzano et al.The inverted model for the top 15 meters of the sub-seabed agrees with the local lithological information and core-log data. Thus we can obtain a detailed remote characterisation of the shallow sediments using a multi-channel sub-bottom profiler within a reasonable computing cost and with minimal pre-processing. This has the potential to reduce the need of extensive geotechnical coring campaigns.

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Theoretical background for continental- and global-scale full-waveform inversion in the time-frequency domain

Cited by 249 publications

References 78 publications

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

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

The imprint of crustal density heterogeneities on regional seismic wave propagation

Pre-stack full waveform inversion of ultra-high-frequency marine seismic reflection data

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