Seismic Imaging of Small Faults in Coal Seams by Prestack Time Migration

2014 ◽  
Vol 556-562 ◽  
pp. 592-596
Author(s):  
Su Zhen Shi ◽  
Juan Li ◽  
Yi Chen Zhao ◽  
Li Biao Yang ◽  
Yao Tang ◽  
...  
Keyword(s):  
Root Mean Square ◽  
Seismic Data ◽  
Mean Square ◽  
Root Mean Square Velocity ◽  
Coal Seams ◽  
Time Migration ◽  
Geological Conditions ◽  
Small Fault ◽  
Prestack Time Migration ◽  
And Migration

In order to improve imaging precision of small structures and small fault blocks of coal seams, the prestack time migration method is used for imaging. Preserved amplitude processing (PAP) is applied to prestack gather firstly after geological data and original seismic data of the exploration area are fully understood. Initial root mean square velocity field is established through the method of picking up root mean square velocity on CRP gather. Then, a precise root mean square velocity model is created after continuous iteration and modification. Meanwhile, appropriate algorithm and migration parameters are selected during the migration process. Finally, the imaging of small fault blocks and small faults in the prestack time migration section is clear and migration is highly coinciding with the case disclosed by boreholes. It’s proved that prestack time migration is especially suitable for processing 3D seismic data of small faults and small fault blocks in coal seams with complicated geological conditions.

3D constraints and finite-difference modeling of massive sulfide deposits: The Kristineberg seismic lines revisited, northern Sweden

Geophysics ◽  
2012 ◽  
Vol 77 (5) ◽  
pp. WC69-WC79 ◽  
Author(s):  
Mahdieh Dehghannejad ◽  
Alireza Malehmir ◽  
Christopher Juhlin ◽  
Pietari Skyttä
Keyword(s):  
Finite Difference ◽  
Seismic Data ◽  
Massive Sulfide ◽  
Northern Sweden ◽  
Seismic Reflection Data ◽  
Sulfide Deposits ◽  
Time Migration ◽  
Massive Sulfide Deposits ◽  
Prestack Time Migration ◽  
Seismic Lines

The Kristineberg mining area in the western part of the Skellefte ore district is the largest base metal producer in northern Sweden and currently the subject of extensive geophysical and geologic studies aimed at constructing 3D geologic models. Seismic reflection data form the backbone of the geologic modeling in the study area. A geologic cross section close to the Kristineberg mine was used to generate synthetic seismic data using acoustic and elastic finite-difference algorithms to provide further insight about the nature of reflections and processing challenges when attempting to image the steeply dipping structures within the study area. Synthetic data suggest processing artifacts manifested themselves in the final 2D images as steeply dipping events that could be confused with reflections. Fewer artifacts are observed when the data are processed using prestack time migration. Prestack time migration also was performed on high-resolution seismic data recently collected near the Kristineberg mine and helped to image a high-amplitude, gently dipping reflection occurring stratigraphically above the extension of the deepest Kristineberg deposit. Swath 3D processing was applied to two crossing seismic lines, west of the Kristineberg mine, to provide information on the 3D geometry of an apparently flat-lying reflection observed in both of the profiles. The processing indicated that the reflection dips about 30° to the southwest and is generated at the contact between metasedimentary and metavolcanic rocks, the upper part of the latter unit being the most typical stratigraphic level for the massive sulfide deposits in the Skellefte district.

Fast collocation for Moho estimation from GOCE gravity data: the Iran case study

2020 ◽  
Vol 221 (1) ◽  
pp. 651-664
Author(s):  
H Heydarizadeh Shali ◽  
D Sampietro ◽  
A Safari ◽  
M Capponi ◽  
A Bahroudi
Keyword(s):  
Root Mean Square ◽  
Root Mean Square Deviation ◽  
Seismic Data ◽  
Active Faults ◽  
Earth’S Crust ◽  
Arabian Plate ◽  
Moho Depth ◽  
Mean Square ◽  
Mean Square Deviation ◽  
Earth's Crust

SUMMARY The study of the discontinuity between crust and mantle beneath Iran is still an open issue in the geophysical community due to its various tectonic features created by the collision between the Iranian and Arabian Plate. For instance in regions such as Zagros, Alborz or Makran, despite the number of studies performed, both by exploiting gravity or seismic data, the depth of the Moho and also interior structure is still highly uncertain. This is due to the complexity of the crust and to the presence of large short wavelength signals in the Moho depth. GOCE observations are capable and useful products to describe the Earth’s crust structure either at the regional or global scale. Furthermore, it is plausible to retrieve important information regarding the structure of the Earth’s crust by combining the GOCE observations with seismic data and considering additional information. In the current study, we used as observation a grid of second radial derivative of the anomalous gravitational potential computed at an altitude of 221 km by means of the space-wise approach, to study the depth of the Moho. The observations have been reduced for the gravitational effects of topography, bathymetry and sediments. The residual gravity has been inverted accordingly to a simple two-layer model. In particular, this guarantees the uniqueness of the solution of the inverse problem which has been regularized by means of a collocation approach in the frequency domain. Although results of this study show a general good agreement with seismically derived depths with a root mean square deviation of 6 km, there are some discrepancies under the Alborz zone and also Oman sea with a root mean square deviation up 10 km for the former and an average difference of 3 km for the latter. Further comparisons with the natural feature of the study area, for instance, active faults, show that the resulting Moho features can be directly associated with geophysical and tectonic blocks.

scholarly journals Effect of scanning speed on texture-elicited vibrations

2020 ◽  
Vol 17 (167) ◽  
pp. 20190892
Author(s):  
Charles M. Greenspon ◽  
Kristine R. McLellan ◽  
Justin D. Lieber ◽  
Sliman J. Bensmaia
Keyword(s):  
Root Mean Square ◽  
Laser Doppler Vibrometer ◽  
Scanning Speed ◽  
Mean Square ◽  
Root Mean Square Velocity ◽  
Dependent Change ◽  
Fine Surface ◽  
Neuronal Representation ◽  
Human Participants ◽  
Exploratory Movements

To sense the texture of a surface, we run our fingers across it, which leads to the elicitation of skin vibrations that depend both on the surface and on exploratory parameters, particularly scanning speed. The transduction and processing of these vibrations mediate the ability to discern fine surface features. The objective of the present study is to characterize the effect of changes in scanning speed on texture-elicited vibrations to better understand how the exploratory movements shape the neuronal representation of texture. To this end, we scanned a variety of textures across the fingertip of human participants at a variety of speeds (10–160 mm s −1 ) while measuring the resulting vibrations using a laser Doppler vibrometer. First, we found that the intensity of the vibrations—as indexed by root-mean-square velocity—increases with speed but that the skin displacement remains constant. Second, we found that the frequency composition of the vibrations shifts systematically to higher frequencies with increases in scanning speed. Finally, we show that the speed-dependent shift in frequency composition accounts for the speed-dependent change in intensity.

Enhancements to prestack frequency‐wavenumber (f-k) migration

Geophysics ◽  
1991 ◽  
Vol 56 (1) ◽  
pp. 27-40 ◽  
Author(s):  
Z. Li ◽  
W. Lynn ◽  
R. Chambers ◽  
Ken Larner ◽  
Ray Abma
Keyword(s):  
Computational Effort ◽  
Velocity Variation ◽  
Lateral Velocity ◽  
Time Migration ◽  
Migration Velocity Analysis ◽  
Prestack Time Migration ◽  
And Migration ◽  
Definition Of ◽  
Ray Bending ◽  
Excellent Source

Prestack frequency‐wavenumber (f-k) migration is a particularly efficient method of doing both full prestack time migration and migration velocity analysis. Conventional implementations of the method, however, can encounter several drawbacks: (1) poor resolution and spatial aliasing noise caused by insufficient sampling in the offset dimension, (2) poor definition of steep events caused by insufficient sampling in the velocity dimension, and (3) inadequate handling of ray bending for steep events. All three of these problems can be mitigated with modifications to the prestack f-k algorithm. The application of linear moveout (LMO) in the offset dimension prior to migration reduces event moveout and hence increases the bandwidth of non‐spatially aliased signals. To reduce problems of interpolation for steep events, the number of constant‐velocity migrations can be economically increased by performing residual poststack migrations. Finally, migration with a dip‐dependent imaging velocity addresses the issue of ray bending and thereby improves the positioning of steep events. None of these enhancements substantially increases the computational effort of f-k migration. Prestack f-k migration possesses a limitation for which no solution is readily available. Where lateral velocity variation is modest, steep events (such as fault‐plane reflections in sediments) may not be imaged as well as by other migration approaches. This shortcoming results from the restriction that, in the prestack f-k approach, a single velocity field must serve to perform two different functions: imaging and stacking. Nevertheless, in areas of strong velocity variation and gentle to moderate dip, the detailed velocity control afforded by the prestack f-k method is an excellent source of geologic information.

scholarly journals The offset-midpoint traveltime pyramid of P-waves in homogeneous orthorhombic media

Geophysics ◽  
2016 ◽  
Vol 81 (5) ◽  
pp. C151-C162 ◽  
Author(s):  
Qi Hao ◽  
Alexey Stovas ◽  
Tariq Alkhalifah
Keyword(s):  
P Wave ◽  
Analytic Approximation ◽  
Velocity Analysis ◽  
P Waves ◽  
Time Migration ◽  
Migration Velocity Analysis ◽  
Analytic Expressions ◽  
Prestack Time Migration ◽  
And Migration ◽  
Homogeneous Media

The offset-midpoint traveltime pyramid describes the diffraction traveltime of a point diffractor in homogeneous media. We have developed an analytic approximation for the P-wave offset-midpoint traveltime pyramid for homogeneous orthorhombic media. In this approximation, a perturbation method and the Shanks transform were implemented to derive the analytic expressions for the horizontal slowness components of P-waves in orthorhombic media. Numerical examples were shown to analyze the proposed traveltime pyramid formula and determined its accuracy and the application in calculating migration isochrones and reflection traveltime. The proposed offset-midpoint traveltime formula is useful for Kirchhoff prestack time migration and migration velocity analysis for orthorhombic media.

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