Use of Data Compression in Gaussian Beam Migration Algorithm

2018 ◽  
Author(s):  
R. Lencrerot ◽  
L. Qu ◽  
B. Duquet ◽  
C. Agut
Keyword(s):  
Data Compression ◽  
Gaussian Beam ◽  
Use Of Data ◽  
Gaussian Beam Migration

Gaussian beam migration

Geophysics ◽  
1990 ◽  
Vol 55 (11) ◽  
pp. 1416-1428 ◽  
Author(s):  
N. Ross Hill
Keyword(s):  
Gaussian Beam ◽  
Wave Field ◽  
Seismic Source ◽  
Velocity Model ◽  
Downward Continuation ◽  
Gaussian Beams ◽  
Seismic Velocities ◽  
Migration Method ◽  
Gaussian Beam Migration ◽  
Lateral Variations

Just as synthetic seismic data can be created by expressing the wave field radiating from a seismic source as a set of Gaussian beams, recorded data can be downward continued by expressing the recorded wave field as a set of Gaussian beams emerging at the earth’s surface. In both cases, the Gaussian beam description of the seismic‐wave propagation can be advantageous when there are lateral variations in the seismic velocities. Gaussian‐beam downward continuation enables wave‐equation calculation of seismic propagation, while it retains the interpretive raypath description of this propagation. This paper describes a zero‐offset depth migration method that employs Gaussian beam downward continuation of the recorded wave field. The Gaussian‐beam migration method has advantages for imaging complex structures. Like finite‐difference migration, it is especially compatible with lateral variations in velocity, but Gaussian beam migration can image steeply dipping reflectors and will not produce unwanted reflections from structure in the velocity model. Unlike other raypath methods, Gaussian beam migration has guaranteed regular behavior at caustics and shadows. In addition, the method determines the beam spacing that ensures efficient, accurate calculations. The images produced by Gaussian beam migration are usually stable with respect to changes in beam parameters.

‘Modulation’ by Richard Powers: Digital sound, compression and the short story

2021 ◽  
Vol 11 (1-2) ◽  
pp. 161-176
Author(s):  
Michael Hedges
Keyword(s):  
Data Compression ◽  
Short Story ◽  
Original Music ◽  
Richard Powers ◽  
Recording Industry ◽  
File Size ◽  
Cultural Artifact ◽  
Use Of Data ◽  
Music File ◽  
Digital Sound

This article presents a reading of ‘Modulation’ (2008) by Richard Powers. Firstly, I consider the short story’s representation of the MP3 music file, specifically its effects on how music is circulated and stored, as well as how it sounds. These changes are the result of different processes of compression. The MP3 format makes use of data compression to reduce the file size of a digital recording significantly. Such a loss of information devises new social and material relations between what remains of the original music, the recording industry from which MP3s emerged and the online markets into which they enter. I argue that ‘Modulation’ is a powerful evocation of a watershed moment in how we consume digital sound: what Jonathan Sterne has termed the rise of the MP3 as ‘cultural artifact’. I contend that the short story, like the MP3, is also a compressed manner of representation. I use narrative theory and short story criticism to substantiate this claim, before positioning ‘Modulation’ alongside Powers’s novels of information. I conclude by suggesting that ‘Modulation’ offers an alternative to representing information through an excess of data. This article reads Powers’s compressed prose as a formal iteration of the data compression the story narrates.

scholarly journals Target-oriented Gaussian beam migration using a modified ray tracing scheme

2019 ◽  
Vol 16 (6) ◽  
pp. 1301-1319 ◽  
Author(s):  
Rui Zhang ◽  
Jian-Ping Huang ◽  
Su-Bin Zhuang ◽  
Zhen-Chun Li
Keyword(s):  
Gaussian Beam ◽  
Ray Tracing ◽  
Large Scale ◽  
High Efficiency ◽  
Complex Structure ◽  
Back Propagation ◽  
Imaging Method ◽  
Computation Efficiency ◽  
Simple Implementation ◽  
Gaussian Beam Migration

Abstract For large-scale 3D seismic data, target-oriented reservoir imaging is more attractive than conventional full-volume migration, in terms of computation efficiency. Gaussian beam migration (GBM) is one of the most robust depth imaging method, which not only keeps the advantages of ray methods, such as high efficiency and flexibility, but also allows us to solve caustics and multipathing problems. But conventional Gaussian beam migration requires slant stack for prestack data, and ray tracing from beam center location to subsurface, which is not easy to be directly applied for target-oriented imaging. In this paper, we modify the conventional Gaussian beam migration scheme, by shooting rays from subsurface image points to receivers to implement wavefield back-propagation. This modification helps us to achieve a better subsurface illumination in complex structure and allows simple implementation for target reservoir imaging. Significantly, compared with the wavefield-based GBM, our method does not reconstruct the subsurface snapshots, which has higher efficiency. But the proposed method is not as efficient as the conventional Gaussian beam migration. Synthetic and field data examples demonstrate the validity and the target-oriented imaging capability of our method.

An efficient ray-tracing method and its application to Gaussian beam migration in complex multilayered anisotropic media

Geophysics ◽  
2018 ◽  
Vol 83 (5) ◽  
pp. T281-T289 ◽  
Author(s):  
Qianru Xu ◽  
Weijian Mao
Keyword(s):  
Gaussian Beam ◽  
Ray Tracing ◽  
Initial Conditions ◽  
Anisotropic Media ◽  
Memory Storage ◽  
Ray Tracing Method ◽  
Embedded Discontinuities ◽  
Model Parameterization ◽  
Gaussian Beam Migration ◽  
Tracing Method

We have developed a fast ray-tracing method for multiple layered inhomogeneous anisotropic media, based on the generalized Snell’s law. Realistic geologic structures continuously varying with embedded discontinuities are parameterized by adopting cubic B-splines with nonuniformly spaced nodes. Because the anisotropic characteristic is often closely related to the interface configuration, this model parameterization scheme containing the natural inclination of the corresponding layer is particularly suitable for tilted transverse isotropic models whose symmetry axis is generally perpendicular to the direction of the layers. With this model parameterization, the first- and second-order spatial derivatives of the velocity within the interfaces can be effectively obtained, which facilitates the amplitude computation in dynamic ray tracing. By using complex initial conditions for the dynamic ray system and taking the multipath effect into consideration, our method is applicable to Gaussian beam migration. Numerical experiments of our method have been used to verify its effectiveness, practicability, and efficiency in memory storage and computation.

scholarly journals Data Compression for Remote Laboratories

2017 ◽  
Vol 11 (4) ◽  
pp. 95
Author(s):  
Olawale Babatunde Akinwale ◽  
Lawrence Olakunle Kehinde
Keyword(s):  
Data Compression ◽  
Mobile Phones ◽  
Use Of Data ◽  
Remote Laboratories ◽  
Remote Lab ◽  
Remote Labs ◽  
The Cost

Remote laboratories on mobile phones have been around for a few years now. This has greatly improved accessibility of these remote labs to students who cannot afford computers but have mobile phones. When money is a factor however (as is often the case with those who can’t afford a computer), the cost of use of these remote laboratories should be minimized. This work addressed this issue of minimizing the cost of use of the remote lab by making use of data compression for data sent between the user and remote lab.

2D anisotropic multicomponent Gaussian-beam migration under complex surface conditions

Geophysics ◽  
2020 ◽  
Vol 85 (2) ◽  
pp. S89-S102 ◽  
Author(s):  
Jianguang Han ◽  
Qingtian Lü ◽  
Bingluo Gu ◽  
Jiayong Yan ◽  
Hao Zhang
Keyword(s):  
Gaussian Beam ◽  
Complex Surface ◽  
Dynamic Features ◽  
Surface Conditions ◽  
Depth Migration ◽  
Surface Areas ◽  
Local Plane ◽  
Gaussian Beam Migration ◽  
Wave Migration ◽  
Irregular Topography

Elastic-wave migration in anisotropic media is a vital challenge, particularly for areas with irregular topography. Gaussian-beam migration (GBM) is an accurate and flexible depth migration technique, which is adaptable for imaging complex surface areas. It retains the dynamic features of the wavefield and overcomes the multivalued traveltimes and caustic problems of Kirchhoff migration. We have extended the GBM method to work for 2D anisotropic multicomponent migration under complex surface conditions. We use Gaussian beams to calculate the wavefield from irregular topography, and we use two schemes to derive the down-continued recorded wavefields. One is based on the local slant stack as in classic GBM, in which the PP- and PS-wave seismic records within the local region are directly decomposed into local plane-wave components from irregular topography. The other scheme does not perform the local slant stack. The Green’s function is calculated with a Gaussian beam summation emitted from the receiver point at the irregular surface. Using the crosscorrelation imaging condition and combining with the 2D anisotropic ray-tracing algorithm, we develop two 2D anisotropic multicomponent Gaussian-beam prestack depth migration (GB-PSDM) methods, i.e., using the slant stack and nonslant stack, for irregular topography. Numerical tests demonstrate that our anisotropic multicomponent GB-PSDM can accurately image subsurface structures under complex topography conditions.

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