Specular ray parameter extraction and stationary‐phase migration

Geophysics ◽  
2004 ◽  
Vol 69 (1) ◽  
pp. 249-256 ◽  
Author(s):  
Jing Chen
Keyword(s):  
Stationary Phase ◽  
Seismic Reflection ◽  
Parameter Extraction ◽  
Phase Approximation ◽  
Full Data ◽  
Prestack Depth Migration ◽  
Depth Migration ◽  
Kirchhoff Type ◽  
Migration Operator ◽  
Ray Parameter

The Kirchhoff‐type prestack depth migration operator is a diffraction stack of seismic reflection energies over seismic traces. Typically, the diffraction stack is carried out over the full data aperture, producing not only images of reflectors but also aliasing artifacts. Aliasing artifacts often break reflector continuity in images. The stationary‐phase approximation to the migration operator shows that, for image points on reflectors, traces within the neighborhood of specular rays contribute most to the diffraction stack. Traces outside this vicinity introduce aliasing artifacts into the image, especially in the case of coarse trace spacing and aperture truncation. A new migration algorithm, denoted as stationary‐phase migration, is proposed to find the specular ray parameters and then to migrate the specular‐ray energies and reject nonspecular ray energies to yield images with less aliasing.

scholarly journals Depth characterization of shallow aquifers with seismic reflection, Part II—Prestack depth migration and field examples

Geophysics ◽  
2002 ◽  
Vol 67 (1) ◽  
pp. 98-109 ◽  
Author(s):  
John H. Bradford ◽  
D. S. Sawyer
Keyword(s):  
Seismic Reflection ◽  
Water Saturation ◽  
Compressional Wave ◽  
Unconsolidated Sediments ◽  
Prestack Depth Migration ◽  
Improve Image Quality ◽  
Depth Migration ◽  
Shallow Seismic ◽  
Partial Water

It is common in shallow seismic studies for the compressional‐wave velocity in unconsolidated sediments to increase by a factor of four or more at the transition from dry or partial water saturation to full saturation. Under these conditions, conventional NMO velocity analysis fails and leads to large depth and layer thickness estimates if the Dix equation is assumed valid. Prestack depth migration (PSDM) is a means of improving image accuracy. A comparison of PSDM with conventional NMO processing for three field examples from differing hydrogeologic environments illustrates that PSDM can significantly improve image quality and accuracy.

An optimal true‐amplitude least‐squares prestack depth‐migration operator

Geophysics ◽  
1999 ◽  
Vol 64 (2) ◽  
pp. 508-515 ◽  
Author(s):  
Guy Chavent ◽  
René‐Edouard Plessix
Keyword(s):  
Least Squares ◽  
Ray Tracing ◽  
Forward Model ◽  
Weight Matrix ◽  
Prestack Depth Migration ◽  
Depth Migration ◽  
Migration Operator ◽  
Amplitude Correction ◽  
Points Approximation ◽  
The Cost

In order to define an optimal true‐amplitude prestack depth migration for multishot and multitrace data, we develop a general methodology based on the least‐squares data misfit function associated with a forward model. The amplitude of the migrated events are restored at best for any given geometry and any given preliminary filtering and amplitude correction of the data. The migrated section is then the gradient of the cost function multiplied by a weight matrix. A study of the Hessian associated with this data misfit shows how efficiently to find a good weight matrix via the computation of only few elements of this Hessian. Thanks to this matrix, the resulting migration operator is optimal in the sense that it ensures the best possible restoration of the amplitudes among the large class of least‐squares migrations. Applied to a forward model based on Born, ray tracing, and diffracting points approximation, this optimal migration outperforms or at least equals the classic Kirchhoff formula, since the latter belongs to the class of least‐squares migrations and is only optimal for one shot and an infinite aperture. Numerical results illustrate this construction and confirm the above expectations.

scholarly journals Imaging complex structure in shallow seismic-reflection data using prestack depth migration

Geophysics ◽  
2006 ◽  
Vol 71 (6) ◽  
pp. B175-B181 ◽  
Author(s):  
John H. Bradford ◽  
Lee M. Liberty ◽  
Mitch W. Lyle ◽  
William P. Clement ◽  
Scott Hess
Keyword(s):  
Seismic Reflection ◽  
Complex Structure ◽  
Volcanic Rocks ◽  
Depth Range ◽  
Prestack Depth Migration ◽  
Measured Velocity ◽  
Seismic Reflection Data ◽  
Depth Migration ◽  
Time Migration ◽  
Shallow Seismic

Prestack depth migration (PSDM) analysis has the potential to significantly improve the accuracy of both shallow seismic reflection images and the measured velocity distributions. In a study designed to image faults in the Alvord Basin, Oregon, at depths from [Formula: see text], PSDM produced a detailed reflection image over the full target depth range. In contrast, poststack time migration produced significant migration artifacts in the upper [Formula: see text] that obscured reflection events and limited the structural interpretation in the shallow section. Additionally, an abrupt increase from [Formula: see text] to [Formula: see text] in the PSDM velocity model constrained the interpretation of the transition from sedimentary basin fill to basement volcanic rocks. PSDM analysis revealed a complex extensional history with at least two distinct phases of basin growth and a midbasin basement high that forms the division between two major basin compartments.

On: “Pulse distortion in depth migration,” M. Tygel, J. Schleicher, and P. Hubral (October 1994 GEOPHYSICS, 59, p. 1561–1569).

Geophysics ◽  
1995 ◽  
Vol 60 (6) ◽  
pp. 1942-1944 ◽  
Author(s):  
Arthur E. Barnes
Keyword(s):  
Seismic Reflection ◽  
Prestack Depth Migration ◽  
Seismic Reflection Data ◽  
Depth Migration ◽  
Reflection Data ◽  
Time Migration ◽  
Pulse Distortion ◽  
Nmo Stretch ◽  
Frequency Shifting

Tygel et al. have written an excellent and rigorous discussion of pulse distortion in seismic reflection data caused by prestack depth migration. Such distortion is easily understood by recognizing that it is more or less the same effect as normal moveout (NMO) stretch combined with frequency shifting due to poststack time migration.

3-D preserved amplitude prestack depth migration on a workstation

Geophysics ◽  
1999 ◽  
Vol 64 (1) ◽  
pp. 222-229 ◽  
Author(s):  
Philippe Thierry ◽  
Gilles Lambaré ◽  
Pascal Podvin ◽  
Mark S. Noble
Keyword(s):  
Seismic Reflection ◽  
Velocity Fields ◽  
Prestack Depth Migration ◽  
Data Set ◽  
Seismic Reflection Data ◽  
Depth Migration ◽  
Cpu Time ◽  
Reflection Data ◽  
Marine Data ◽  
Single Processor

We present an algorithm based on the ray+Born approximation for 3-D preserved amplitude prestack depth migration (PAPsDM) of seismic reflection data. This ray+Born inversion scheme allows the quantitative recovery of model perturbations. The Green’s functions are estimated by dynamic ray tracing in 3-D heterogeneous smooth velocity fields with a wavefront construction (WFC) method. The PAPsDM algorithm was implemented on a single‐processor Sun Sparc 20 workstation. Special attention was paid to CPU efficiency and memory requirements. We present an application on a 3-D real marine data set (13 Gbytes). About one week of CPU time is needed to obtain a migrated image of 7 × 1 × 1 km.

Coal seismic surveying over near-surface basalts: Experience from Central Queensland, Australia

Geophysics ◽  
2014 ◽  
Vol 79 (2) ◽  
pp. B109-B122 ◽  
Author(s):  
Binzhong Zhou ◽  
Peter Hatherly ◽  
Troy Peters ◽  
Weijia Sun
Keyword(s):  
Surface Waves ◽  
Seismic Reflection ◽  
Unconsolidated Sediments ◽  
Successful Outcome ◽  
Low Velocity ◽  
Prestack Depth Migration ◽  
Seismic Line ◽  
Near Surface ◽  
Depth Migration ◽  
Seismic Surveying

Seismic reflection surveying in basalt-covered areas often fails to image underlying reflectors. To gain insights into the nature of the problem and obtain potential solutions, we have conducted experimental 2D seismic reflection and offset VSP surveys at two coal mines in the Bowen Basin of Australia. At the first mine, the basalt is relatively deep (114 m) and relatively thin (20 m). Conventional seismic acquisition and processing of a 2D seismic line provide poor results. However, upgoing reflections from layers below the basalt are clearly evident in the VSP survey and prestack depth migration is able to improve the continuity of the reflectors beneath the basalt. At the second mine, the 360 m wide basalt is at a depth of 40 m and has a thickness of about 40 m. It is fresh and unweathered and consists of multiple flows which are interlayered with unconsolidated sediments. Long-offset data acquisition combined with prestack depth migration was expected to produce satisfactory results but this is not the case. The associated VSP survey suggests that the problems at this mine are due to (1) the generation of complex downgoing and upgoing wave-fields within the basalt and (2) significant scattering of surface waves from outside the basalt at the margins of the basalt. Another problem is that the target coal seams are at about 300 m depth and the muting required to remove refraction events limited the effectiveness of the prestack depth migration. Reducing the strength of the surface waves through selection of an appropriate source and placement of shots at the base of the low-velocity zone (as had been the case at the first mine) will therefore improve the chances for a successful outcome. A Vibroseis survey subsequently undertaken at the second mine, which produced shot records with reduced surface waves, shows this to be the case.

Kinematic interpretation in the prestack depth‐migrated domain

Geophysics ◽  
1997 ◽  
Vol 62 (4) ◽  
pp. 1226-1237 ◽  
Author(s):  
Irina Apostoiu‐Marin ◽  
Andreas Ehinger
Keyword(s):  
Signal To Noise Ratio ◽  
Velocity Model ◽  
Point Of View ◽  
Prestack Depth Migration ◽  
Depth Migration ◽  
Velocity Models ◽  
Time Domain Data ◽  
And Migration ◽  
Point To Point ◽  
Homogeneous Media

Prestack depth migration can be used in the velocity model estimation process if one succeeds in interpreting depth events obtained with erroneous velocity models. The interpretational difficulty arises from the fact that migration with erroneous velocity does not yield the geologically correct reflector geometries and that individual migrated images suffer from poor signal‐to‐noise ratio. Moreover, migrated events may be of considerable complexity and thus hard to identify. In this paper, we examine the influence of wrong velocity models on the output of prestack depth migration in the case of straight reflector and point diffractor data in homogeneous media. To avoid obscuring migration results by artifacts (“smiles”), we use a geometrical technique for modeling and migration yielding a point‐to‐point map from time‐domain data to depth‐domain data. We discover that strong deformation of migrated events may occur even in situations of simple structures and small velocity errors. From a kinematical point of view, we compare the results of common‐shot and common‐offset migration. and we find that common‐offset migration with erroneous velocity models yields less severe image distortion than common‐shot migration. However, for any kind of migration, it is important to use the entire cube of migrated data to consistently interpret in the prestack depth‐migrated domain.

Inelastic eikonal phenomenology in a stationary-phase approximation

1975 ◽  
Vol 12 (7) ◽  
pp. 2031-2036 ◽  
Author(s):  
Hector Moreno ◽  
H. M. Fried
Keyword(s):  
Stationary Phase ◽  
Phase Approximation
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