Asymptotically linear velocity analysis with high resolution in time domain

Geophysics ◽  
1991 ◽  
Vol 56 (11) ◽  
pp. 1840-1848 ◽  
Author(s):  
Simon Katz
Keyword(s):  
Penalty Function ◽  
Time Domain ◽  
Noise Suppression ◽  
Signal To Noise Ratio ◽  
Linear Velocity ◽  
Velocity Analysis ◽  
Signal To Noise ◽  
Ratio Estimate ◽  
Analysis Technique ◽  
Noise Ratio

A new method of velocity analysis based on the joint use of a linear velocity analysis technique and a nonlinear penalty function is described. The penalty function is defined as a monotonic continuous function of the signal‐to‐noise ratio estimate, tending to a constant or to zero with this estimate converging respectively to infinity or to zero. The signal‐to‐noise ratio estimate is obtained as the ratio of the estimates of the energy of the signal with given velocity and the energy of the residual field. The resulting velocity analysis technique is characterized by higher noise suppression and higher resolution in the velocity and the time domain compared to the semblance based velocity analysis or the velocity analysis based on the slant stacking of input data.

scholarly journals Study on the Velocity Analysis Method of Low SNR Seismic Data

2021 ◽  
Vol 11 (1) ◽  
pp. 78
Author(s):  
Jianbo He ◽  
Zhenyu Wang ◽  
Mingdong Zhang
Keyword(s):  
Seismic Data ◽  
Fresnel Zone ◽  
Signal To Noise Ratio ◽  
Normal Wave ◽  
Curvature Radius ◽  
Velocity Spectrum ◽  
Velocity Analysis ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Zero Offset

When the signal to noise ratio of seismic data is very low, velocity spectrum focusing will be poor., the velocity model obtained by conventional velocity analysis methods is not accurate enough, which results in inaccurate migration. For the low signal noise ratio (SNR) data, this paper proposes to use partial Common Reflection Surface (CRS) stack to build CRS gathers, making full use of all of the reflection information of the first Fresnel zone, and improves the signal to noise ratio of pre-stack gathers by increasing the number of folds. In consideration of the CRS parameters of the zero-offset rays emitted angle and normal wave front curvature radius are searched on zero offset profile, we use ellipse evolving stacking to improve the zero offset section quality, in order to improve the reliability of CRS parameters. After CRS gathers are obtained, we use principal component analysis (PCA) approach to do velocity analysis, which improves the noise immunity of velocity analysis. Models and actual data results demonstrate the effectiveness of this method.

scholarly journals Applications of Continuous Wave Free Precession Sequences in Low-Field, Time-Domain NMR

2019 ◽  
Vol 9 (7) ◽  
pp. 1312 ◽  
Author(s):  
Tiago Bueno Moraes ◽  
Tatiana Monaretto ◽  
Luiz Colnago
Keyword(s):  
Time Domain ◽  
Continuous Wave ◽  
Signal To Noise Ratio ◽  
Flip Angle ◽  
Time Interval ◽  
Single Shot ◽  
Free Precession ◽  
Signal To Noise ◽  
Low Field ◽  
Noise Ratio

This review discusses the theory and applications of the Continuous Wave Free Precession (CWFP) sequence in low-field, time-domain nuclear magnetic resonance (TD-NMR). CWFP is a special case of the Steady State Free Precession (SSFP) regime that is obtained when a train of radiofrequency pulses, separated by a time interval Tp shorter than the effective transverse relaxation time (T2*), is applied to a sample. Unlike regular pulsed experiments, in the CWFP regime, the amplitude is not dependent on T1. Therefore, Tp should be as short as possible (limited by hardware). For Tp < 0.5 ms, thousands of scans can be performed per second, and the signal to noise ratio can be enhanced by more than one order of magnitude. The amplitude of the CWFP signal is dependent on T1/T2; therefore, it can be used in quantitative analyses for samples with a similar relaxation ratio. The time constant to reach the CWFP regime (T*) is also dependent on relaxation times and flip angle (θ). Therefore, T* has been used as a single shot experiment to measure T1 using a low flip angle (5°) or T2, using θ = 180°. For measuring T1 and T2 simultaneously in a single experiment, it is necessary to use θ = 90°, the values of T* and M0, and the magnitude of CWFP signal |Mss|. Therefore, CWFP is an important sequence for TD-NMR, being an alternative to the Carr-Purcell-Meiboom-Gill sequence, which depends only on T2. The use of CWFP for the improvement of the signal to noise ratio in quantitative and qualitative analyses and in relaxation measurements are presented and discussed.

Measurement of Signal-to-Noise Ratio and Signal-to-Noise and Distortion Ratio Using Histogram Test in Time Domain Analysis

2021 ◽  
pp. 403-410
Author(s):  
Manish Jain ◽  
Prakash Chandra Sharma ◽  
Pradeep Kumar Tiwari ◽  
Rohit Kumar Gupta
Keyword(s):  
Time Domain ◽  
Signal To Noise Ratio ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Signal To Noise ◽  
Noise Ratio

scholarly journals Improving the Signal-to-Noise Ratio of Time Domain Fiber Bragg Grating Sensor Based on Hybrid Simplex and Golay Coding Technique

IEEE Access ◽  
2019 ◽  
Vol 7 ◽  
pp. 167089-167098
Author(s):  
Mohamed M. Elgaud ◽  
Mohd Saiful Dzulkefly Zan ◽  
Abdulfatah Abushagur Ghaith ◽  
Ahmad Ashrif A. Bakar ◽  
Norhana Arsad ◽  
...  
Keyword(s):  
Fiber Bragg Grating ◽  
Time Domain ◽  
Signal To Noise Ratio ◽  
Fiber Bragg Grating Sensor ◽  
Bragg Grating ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Bragg Grating Sensor

scholarly journals Enhancement of signal-to-noise ratio in Brillouin optical time domain analyzers by dual-probe detection

2017 ◽  
Author(s):  
Haritz Iribas ◽  
Alayn Loayssa ◽  
Florian Sauser ◽  
Miguel Llera ◽  
Sébastien Le Floch
Keyword(s):  
Time Domain ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Probe Detection ◽  
Noise Ratio ◽  
Optical Time ◽  
Dual Probe
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