High-resolution bootstrapped differential semblance

Geophysics ◽  
2012 ◽  
Vol 77 (3) ◽  
pp. U39-U47 ◽  
Author(s):  
Brahim Abbad ◽  
Bjørn Ursin
Keyword(s):  
Time Domain ◽  
Field Data ◽  
Standard Errors ◽  
Velocity Analysis ◽  
Residual Velocity ◽  
Fitting Algorithm ◽  
Parameter Tracking ◽  
Multichannel Data ◽  
Resampling Procedure ◽  
Statistical Resampling

We formulated two coherency measures, based on the bootstrapped differential semblance (BDS) estimator, that offered higher resolution in parameter tracking than did standard normalized differential semblance. Bootstrapping is a statistical resampling procedure used to infer estimates of standard errors and confidence intervals from data samples for which the statistical properties are unattainable via simple means, or when the probability density function is unkown or difficult to estimate. The first proposed estimator was based on a deterministic sorting of original offset traces by alternating near and far offsets to achieve maximized time shifts between adjacent traces. The near offsets were indexed with odd integers, while the even integers were used to index far offsets that were located at a constant index increment from the previous trace. The second was the product of several BDS terms, with the first term being the deterministic BDS defined above. The other terms were generated by random sorting of traces that alternated near and far offsets in an unpredictible manner. The proposed estimators could be applied in building velocity (and anellipticity) spectra for time-domain velocity analysis, depth-domain residual velocity update, or to any parameter-fitting algorithm involving discrete multichannel data. The gain in resolution provided by the suggested estimators over the differential semblance coefficient was illustrated on a number of synthetic and field data examples.

Residual shot profile migration

Geophysics ◽  
1992 ◽  
Vol 57 (6) ◽  
pp. 815-822 ◽  
Author(s):  
Wook B. Lee ◽  
Lin Zhang
Keyword(s):  
Field Data ◽  
Correction Term ◽  
Velocity Analysis ◽  
Residual Velocity ◽  
Migration Technique ◽  
Number Of Iterations

We have developed a residual shot profile migration technique, which consists of dip‐corrected residual normal moveout (NMO) and depth restretching. The dip‐corrected residual NMO equation and the depth restretching equation were derived by generalizing Al‐Yahya’s residual NMO equation. Using the dip‐correction residual NMO equation, velocity errors can be estimated more accurately than without the dip correction term in the residual NMO equation. Residual shot profile migration was applied to migrated prestack data in a manner similar to conventional processing by cascading residual velocity analysis, residual NMO, and stack and depth stretching. With residual migration, we can either avoid remigration of the original prestack data or reduce the number of iterations required to produce a satisfactory image. Residual migration is efficient enough to be implemented on a workstation. Significant improvement in imaging to cases (a pinchout and salt top and bottom) is demonstrated using synthetic and field data examples.

Migration velocity analysis based on focusing diffractions generated using the CRS wavefront attributes: Application to real land data

Geophysics ◽  
2021 ◽  
pp. 1-50
Author(s):  
German Garabito ◽  
José Silas dos Santos Silva ◽  
Williams Lima
Keyword(s):  
Time Domain ◽  
Real Data ◽  
Normal Incidence ◽  
Velocity Model ◽  
Migration Velocity ◽  
Velocity Analysis ◽  
Velocity Models ◽  
Time Migration ◽  
Migration Velocity Analysis ◽  
The Time Domain

In land seismic data processing, the prestack time migration (PSTM) image remains the standard imaging output, but a reliable migrated image of the subsurface depends on the accuracy of the migration velocity model. We have adopted two new algorithms for time-domain migration velocity analysis based on wavefield attributes of the common-reflection-surface (CRS) stack method. These attributes, extracted from multicoverage data, were successfully applied to build the velocity model in the depth domain through tomographic inversion of the normal-incidence-point (NIP) wave. However, there is no practical and reliable method for determining an accurate and geologically consistent time-migration velocity model from these CRS attributes. We introduce an interactive method to determine the migration velocity model in the time domain based on the application of NIP wave attributes and the CRS stacking operator for diffractions, to generate synthetic diffractions on the reflection events of the zero-offset (ZO) CRS stacked section. In the ZO data with diffractions, the poststack time migration (post-STM) is applied with a set of constant velocities, and the migration velocities are then selected through a focusing analysis of the simulated diffractions. We also introduce an algorithm to automatically calculate the migration velocity model from the CRS attributes picked for the main reflection events in the ZO data. We determine the precision of our diffraction focusing velocity analysis and the automatic velocity calculation algorithms using two synthetic models. We also applied them to real 2D land data with low quality and low fold to estimate the time-domain migration velocity model. The velocity models obtained through our methods were validated by applying them in the Kirchhoff PSTM of real data, in which the velocity model from the diffraction focusing analysis provided significant improvements in the quality of the migrated image compared to the legacy image and to the migrated image obtained using the automatically calculated velocity model.

Azimuthal Residual Velocity Analysis in Offset Vector for WAZ Imaging

2010 ◽  
Author(s):  
Didier Lecerf ◽  
Jean-Luc Boelle ◽  
Amhed Belmokhtar ◽  
Abdeljebbar Ladmek
Keyword(s):  
Velocity Analysis ◽  
Residual Velocity

scholarly journals Coupled Harmonic Admittance Identification Based on Least Square Estimation

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2600 ◽  
Author(s):  
Yaqiong Li ◽  
Zhanfeng Deng ◽  
Tongxun Wang ◽  
Guoliang Zhao ◽  
Shengjun Zhou
Keyword(s):  
Equivalent Circuit ◽  
Time Domain ◽  
Field Data ◽  
Mutual Coupling ◽  
Least Square ◽  
Estimation Technique ◽  
Least Square Estimation ◽  
Harmonic Current ◽  
Emission Estimation ◽  
Current Emission

Norton equivalent circuit is a commonly used model in estimating harmonic current emissions of harmonic sources. It however cannot reflect the mutual coupling relationships among voltage and current in different harmonic orders. This paper proposes a new method to identify parameters in a coupled harmonic admittance model. The proposed method is conducted using voltage and current measurements and is based on least square estimation technique. The effectiveness of the method is verified through time-domain simulations for a grid-connected converter and also through field data obtained from a ±800 kV converter station. The experimental results showed that the proposed method presents higher accuracy in terms of harmonic current emission estimation compared with three Norton-base methods.

Poststack velocity analysis by separation and imaging of seismic diffractions

Geophysics ◽  
2007 ◽  
Vol 72 (6) ◽  
pp. U89-U94 ◽  
Author(s):  
Sergey Fomel ◽  
Evgeny Landa ◽  
M. Turhan Taner
Keyword(s):  
High Resolution ◽  
Seismic Data ◽  
Field Data ◽  
Small Scale ◽  
Velocity Analysis ◽  
High Resolution Imaging ◽  
Diffracted Waves ◽  
Resolution Imaging ◽  
Seismic Reflections ◽  
Optimal Focusing

Small geologic features manifest themselves in seismic data in the form of diffracted waves, which are fundamentally different from seismic reflections. Using two field-data examples and one synthetic example, we demonstrate the possibility of separating seismic diffractions in the data and imaging them with optimally chosen migration velocities. Our criteria for separating reflection and diffraction events are the smoothness and continuity of local event slopes that correspond to reflection events. For optimal focusing, we develop the local varimax measure. The objectives of this work are velocity analysis implemented in the poststack domain and high-resolution imaging of small-scale heterogeneities. Our examples demonstrate the effectiveness of the proposed method for high-resolution imaging of such geologic features as faults, channels, and salt boundaries.

scholarly journals High-resolution coherency functionals for velocity analysis: An application for subbasalt seismic exploration

Geophysics ◽  
2013 ◽  
Vol 78 (5) ◽  
pp. U53-U63 ◽  
Author(s):  
Andrea Tognarelli ◽  
Eusebio Stucchi ◽  
Alessia Ravasio ◽  
Alfredo Mazzotti
Keyword(s):  
High Resolution ◽  
Seismic Data ◽  
Field Data ◽  
Signal To Noise Ratio ◽  
Synthetic Seismograms ◽  
Seismic Exploration ◽  
Velocity Analysis ◽  
Signal To Noise ◽  
Geologic Setting ◽  
Analytic Signals

We tested the properties of three different coherency functionals for the velocity analysis of seismic data relative to subbasalt exploration. We evaluated the performance of the standard semblance algorithm and two high-resolution coherency functionals based on the use of analytic signals and of the covariance estimation along hyperbolic traveltime trajectories. Approximate knowledge of the wavelet was exploited to design appropriate filters that matched the primary reflections, thereby further improving the ability of the functionals to highlight the events of interest. The tests were carried out on two synthetic seismograms computed on models reproducing the geologic setting of basaltic intrusions and on common midpoint gathers from a 3D survey. Synthetic and field data had a very low signal-to-noise ratio, strong multiple contamination, and weak primary subbasalt signals. The results revealed that high-resolution coherency functionals were more suitable than semblance algorithms to detect primary signals and to distinguish them from multiples and other interfering events. This early discrimination between primaries and multiples could help to target specific signal enhancement and demultiple operations.

Synthesis of a Time History Based on the Sine-on-Random Prediction Methodology Defined in MIL-STD-810 Method 519

2017 ◽  
Vol 60 (1) ◽  
pp. 31-41
Author(s):  
Michael T. Hale
Keyword(s):  
Time Domain ◽  
Laboratory Tests ◽  
Field Data ◽  
Time History ◽  
Environmental Engineering ◽  
New Technique ◽  
Vibration Test ◽  
Temporal Characteristics ◽  
New Time ◽  
Exponentially Weighted

Abstract Method 519.7, Annex D of MIL-STD-810G, Environmental Engineering Considerations and Laboratory Tests, Change Notice 1 (MIL-STD-810G/CN1) outlines a prediction methodology for establishing a sine-on-random (SoR) structured spectrum that is intended to be representative of gunfire for use in cases in which there is an absence of field data. From that spectrum, the ramp modulated pulse (RMP) technique is proposed as a methodology to synthesize a time history with temporal characteristics that more realistically represent the temporal characteristics of gunfire than that of a SoR time history synthesized via classical SoR generation techniques. This paper provides an alternate technique to the RMP methodology presented in Method 519. The alternate technique is based on normalized exponentially weighted (NEW) time history generated via classical time domain techniques for a SoR vibration test. An outline of the NEW technique and an associated example are provided.

3D generalized nonhyperboloidal moveout approximation

Geophysics ◽  
2017 ◽  
Vol 82 (2) ◽  
pp. C49-C59 ◽  
Author(s):  
Yanadet Sripanich ◽  
Sergey Fomel ◽  
Alexey Stovas ◽  
Qi Hao
Keyword(s):  
Time Domain ◽  
Functional Form ◽  
Seismic Imaging ◽  
High Accuracy ◽  
Velocity Analysis ◽  
Zero Offset ◽  
Independent Parameters

Moveout approximations are commonly used in velocity analysis and time-domain seismic imaging. We revisit the previously proposed generalized nonhyperbolic moveout approximation and develop its extension to the 3D multiazimuth case. The advantages of the generalized moveout approximation are its high accuracy and its ability to reduce to several other known approximations with particular choices of parameters. The proposed 3D functional form involves 17 independent parameters instead of five as in the 2D case. These parameters can be defined by zero-offset traveltime attributes and four additional far-offset rays. In our tests, the proposed approximation achieves significantly higher accuracy than previously proposed 3D approximations.

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