Stratigraphic filtering of seismic waves: The influence of mode conversion multiples onP-wave andS-wave phase and attenuation

1987 ◽  
Vol 125 (5) ◽  
pp. 717-751 ◽  
Author(s):  
I. Lerche
Keyword(s):  
Seismic Waves ◽  
Mode Conversion ◽  
Wave Phase

Sub-basalt Marchenko imaging with offshore Brazil field data

Geophysics ◽  
2021 ◽  
pp. 1-47
Author(s):  
Xueyi Jia ◽  
Anatoly Baumstein ◽  
Charlie Jing ◽  
Erik Neumann ◽  
Roel Snieder
Keyword(s):  
Seismic Waves ◽  
Mode Conversion ◽  
Imaging Techniques ◽  
Hydrocarbon Exploration ◽  
Sampled Data ◽  
Geological Interpretation ◽  
Propagating Waves ◽  
Seismic Acquisition ◽  
Internal Multiples ◽  
Multiple Elimination

Sub-basalt imaging for hydrocarbon exploration faces challenges with the presence of multiple scattering, attenuation and mode-conversion as seismic waves encounter highly heterogeneous and rugose basalt layers. A combination of modern seismic acquisition that can record densely-sampled data, and advanced imaging techniques make imaging through basalt feasible. Yet, the internal multiples, if not properly handled during seismic processing, can be mapped to reservoir layers by conventional imaging methods, misguiding geological interpretation. Traditional internal multiple elimination methods suffer from the requirement of picking horizons of multiple generators and/or a top-down adaptive subtraction process. Marchenko imaging provides an alternative solution to directly remove the artifacts due to internal multiples, without the need of horizon picking or subtraction. In this paper, we present a successful application of direct Marchenko imaging for sub-basalt de-multiple and imaging with an offshore Brazil field dataset. The internal multiples in this example are generated from the seabed and basalt layers, causing severe artifacts in conventional seismic images. We demonstrate that these artifacts are largely suppressed with Marchenko imaging and propose a general work flow for data pre-processing and regularization of marine streamer datasets. We show that horizontally propagating waves can also be reconstructed by the Marchenko method at far offsets.

Azimuthal variations in scattering amplitudes induced by transverse isotropy

Geophysics ◽  
1991 ◽  
Vol 56 (10) ◽  
pp. 1584-1595 ◽  
Author(s):  
M. A. Pelissier ◽  
Anna Thomas‐Betts ◽  
Peter D. Vestergaard
Keyword(s):  
Seismic Waves ◽  
Symmetry Axis ◽  
Mode Conversion ◽  
Transverse Isotropy ◽  
Full Range ◽  
Transversely Isotropic ◽  
Anisotropy Axis ◽  
Scattering Coefficients ◽  
Transversely Isotropic Media ◽  
Isotropic Media

The study of amplitude variations of reflected and transmitted seismic waves due to anistropy has received considerable attention in recent years, but most investigations have concentrated on the effect of transverse isotropy with the symmetry axis either vertical or horizontal. The published results on the whole tend to exclude mode conversions. Amplitudes of all reflected and transmitted wave modes are addressed for [Formula: see text]-waves incident on boundaries between isotropic and transversely isotropic media, the symmetry axis of which is oriented at 45 degrees to the interface. The results cover the full range of incidence angles and all “acquisition azimuth” in the plane of the interface. When the anistropy axis is not normal to the interface, the scattering coefficients are shown to be highly dependent on the azimuth. The pattern of azimuthal variation is especially complicated in the case of mode conversion, and scattering coefficient profiles that are 180 degrees apart are not the same. This has the implication that source‐receiver interchangeability does not hold and could have serious consequences to amplitude studies in split‐spread surveys. Both the [Formula: see text] and [Formula: see text] reflections show strong azimuthal variations, dependent on both the dip and the strike of the anisotropy axis. It may be possible to recover shown that the scattered amplitude patterns are dominantly controlled by the value of the elastic modulus [Formula: see text].

On the Biot slow S-wave

Geophysics ◽  
2008 ◽  
Vol 73 (4) ◽  
pp. N19-N33 ◽  
Author(s):  
Pratap N. Sahay
Keyword(s):  
Strain Rate ◽  
Constitutive Relation ◽  
Seismic Waves ◽  
Mode Conversion ◽  
Shear Mode ◽  
Biot Theory ◽  
Fluid Viscosity ◽  
S Wave ◽  
S Waves ◽  
Coupled Equations

It is accepted widely that the Biot theory predicts only one shear wave representing the in-phase/unison shear motions of the solid and fluid constituent phases (fast S-wave). The Biot theory also contains a shear mode wherein the two constituent phases essentially undergo out-of-phase shear motions (slow S-wave). From the outset of the development of the Biot framework, the existence of this mode has remained unnoticed because of an oversight in decoupling its system of two coupled equations governing shear processes. Moreover, in the absence of the fluid strain-rate term in the Biot constitutive relation, the velocity of this mode is zero. Once the Biot constitutive relation is corrected for the missing fluid strain-rate term (i.e., fluid viscosity), this mode turns out to be, in the inertial regime, a diffusive process akin to a viscous wave in a Newtonian fluid. In the viscous regime, it degenerates to a process governed by a diffusion equation with a damping term. Although this mode is damped so heavily that it dies off rapidly near its source, overlooking its existence ignores a mechanism to draw energy from seismic waves (fast P- and S-waves) via mode conversion at interfaces and at other material discontinuities and inhomogeneities. To illustrate the consequence of generating this mode at an interface, I examine the case of a horizontally polarized fast S-wave normal incident upon a planar air-water interface in a porous medium. Contrary to the classical Biot framework, which suggests that the incident wave should be transmitted practically unchanged through such an interface, the viscosity-corrected Biot framework predicts a strong, fast S-wave reflection because of the slow S-wave generated at the interface.

Galvanomagnetic properties in the spin-density-wave phase of (TMTSF)2PF6

1999 ◽  
Vol 09 (PR10) ◽  
pp. Pr10-247-Pr10-249 ◽  
Author(s):  
B. Korin-Hamzic ◽  
M. Basletić ◽  
N. Francetić ◽  
A. Hamzić ◽  
K. Bechgaard
Keyword(s):  
Spin Density ◽  
Density Wave ◽  
Spin Density Wave ◽  
Wave Phase ◽  
Galvanomagnetic Properties

AN EXPERIMENT WHICH MEASURES RESONANT MODE CONVERSION IN He II

1978 ◽  
Vol 39 (C6) ◽  
pp. C6-228-C6-229
Author(s):  
S. Garrett ◽  
S. Adams ◽  
S. Putterman ◽  
I. Rudnick
Keyword(s):  
Mode Conversion ◽  
Resonant Mode
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