Resolving phase wrapping by using sliding transform for generation of dispersion curves

Geophysics ◽  
2017 ◽  
Vol 82 (3) ◽  
pp. V127-V136 ◽  
Author(s):  
Jyant Kumar ◽  
Tarun Naskar
Keyword(s):  
Spectral Analysis ◽  
Surface Wave ◽  
Surface Waves ◽  
Test Data ◽  
Signal To Noise Ratio ◽  
Phase Unwrapping ◽  
Signal To Noise ◽  
Manual Intervention ◽  
Multichannel Analysis ◽  
Synthetic Test

The complexity involved with the phase unwrapping procedure, while performing the existing spectral analysis of surface waves (SASW) on the basis of two sensors, makes it difficult to automate and requires frequent manual judgment. As a result, this approach generally becomes tedious and may yield erroneous results. The multichannel analysis of surface waves (MASW) technique can resolve the problem of phase wrapping. However, the MASW technique normally requires a large number of closely spaced sensors, typically 24–48 or even more. We have developed a new method that is fast, accurate, and generally resolves the unwrapping of phase with the use of just two sensors, provided the signal-to-noise ratio remains high. In this approach, the unwrapping of the phase can be performed without any manual intervention and an automation of the process becomes feasible. A few examples, involving synthetic test data and surface-wave tests, have been tested to determine the efficacy of our approach. Comparisons of the results have been made with the corresponding solutions using existing SASW and MASW techniques.

Shear Wave Velocity Analysis of 2-D Multichannel Analysis of Surface Wave (MASW) to investigate subsurface Fault of Alternative Bridge Construction in Kelok Sago Jambi

2020 ◽  
Vol 25 (1) ◽  
pp. 18-20
Author(s):  
Muhammad Farhan ◽  
◽  
Gunawan Handayani ◽  
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Wave Velocity ◽  
Urban Areas ◽  
Signal To Noise Ratio ◽  
Body Wave ◽  
Geophysical Methods ◽  
P Wave ◽  
S Wave ◽  
Multichannel Analysis

Every geotechnical measurement requires geophysical methods to classify soil types under the ground. S-wave velocity (Vs), P-wave velocity (Vp), and density (ρ), are the most important parameters in the classification of soils. There are various methods to determine Vs, one of them is P-S logging method. However, this method is less suitable to be applied in urban areas due to the difficulties of data acquisition and high expense in operational costs. In 1999, a seismic method uses surface waves to de-termine Vs profile with a higher signal to noise ratio which was known by the name of Multichannel Analysis of Surface Waves (MASW). A surface wave, especially Rayleigh wave, creeps slowly on the surface with a larger amplitude than a body wave. The wavelengths of the surface wave will disperse in the layers system i.e. the phase velocity of the surface waves is now func-tion of frequency. MASW 2-D method is used in this paper to determine subsoil properties and to identify the fault under the bridge abutments plan (abutment 1 and abutment 2) in Kelok Sago Jambi.

Bearing Fault Detection Using Adaptive Noise Cancelling

1982 ◽  
Vol 104 (2) ◽  
pp. 280-289 ◽  
Author(s):  
G. K. Chaturvedi ◽  
D. W. Thomas
Keyword(s):  
Spectral Analysis ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Primary Input ◽  
Analysis Techniques ◽  
Noise Cancelling ◽  
Adaptive Noise ◽  
Correlated Signals ◽  
Correlated Noises ◽  
Reference Input

The ability to diagnose a mechanical fault is enhanced if the monitoring signal can be preprocessed to reduce the effect of unwanted noise. To this end, the adaptive noise cancelling technique (ANC) can substantially improve the signal to noise ratio where the required signal is contaminated by noise. ANC makes use of two inputs—a primary input which contains the corrupted signal, and a reference input containing noise correlated in some unknown way with the primary noise. A variation of ANC is also proposed and it is shown that this can be applied effectively in those situations where inputs contain correlated signals but uncorrelated or weakly correlated noises. Using vibrational data derived from a reasonably complex bearing rig and preprocessing the data by the ANC technique, this paper shows that the statistical and spectral analysis techniques can be made more effective in their diagnostic roles after the application of ANC.

The lattice filter in ground‐roll suppression

Geophysics ◽  
1994 ◽  
Vol 59 (4) ◽  
pp. 623-631 ◽  
Author(s):  
Ruhi Saatçilar ◽  
Nezihi Canitez
Keyword(s):  
Surface Waves ◽  
Field Data ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Filter Technique ◽  
Lattice Filter ◽  
Ground Roll ◽  
Noise Ratio ◽  
Seismic Reflections

Seismic reflections are sometimes masked by Ray‐leigh‐type surface waves that are termed ground roll in seismic literature. An adaptive lattice filter is used to recover reflected signals contaminated by ground roll. Experiments on synthetic and field data showed that the adaptive lattice filter technique is very effective in ground‐roll elimination. In addition, the filter works as a whitening operator, compresses the signal, and increases the signal‐to‐noise ratio.

scholarly journals Multitaper spectral analysis of atmospheric radar signals

2004 ◽  
Vol 22 (11) ◽  
pp. 3995-4003 ◽  
Author(s):  
V. K. Anandan ◽  
C. J. Pan ◽  
T. Rajalakshmi ◽  
G. Ramachandra Reddy
Keyword(s):  
Spectral Analysis ◽  
Lower Stratosphere ◽  
Signal To Noise Ratio ◽  
Power Spectra ◽  
Estimation Accuracy ◽  
Doppler Width ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Width Measurements ◽  
Backscattered Signals

Abstract. Multitaper spectral analysis using sinusoidal taper has been carried out on the backscattered signals received from the troposphere and lower stratosphere by the Gadanki Mesosphere-Stratosphere-Troposphere (MST) radar under various conditions of the signal-to-noise ratio. Comparison of study is made with sinusoidal taper of the order of three and single tapers of Hanning and rectangular tapers, to understand the relative merits of processing under the scheme. Power spectra plots show that echoes are better identified in the case of multitaper estimation, especially in the region of a weak signal-to-noise ratio. Further analysis is carried out to obtain three lower order moments from three estimation techniques. The results show that multitaper analysis gives a better signal-to-noise ratio or higher detectability. The spectral analysis through multitaper and single tapers is subjected to study of consistency in measurements. Results show that the multitaper estimate is better consistent in Doppler measurements compared to single taper estimates. Doppler width measurements with different approaches were studied and the results show that the estimation was better in the multitaper technique in terms of temporal resolution and estimation accuracy.

A surface wave particle motion discrimination process

1968 ◽  
Vol 58 (2) ◽  
pp. 629-637
Author(s):  
R. S. Simons
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Particle Motion ◽  
Seismic Data ◽  
Digital Computer ◽  
Rayleigh Waves ◽  
Motion Pattern ◽  
Signal To Noise ◽  
Long Period ◽  
Period Data

Abstract A digital computer process is described which examines the three-componen particle-motion pattern of seismic data as a function of frequency and uses this information to discriminate against all motion except surface waves arriving from some pre-assigned direction. Application of the process to long-period data has shown that it can substantially improve the signal-to-noise ratios of Love and Rayleigh waves from earthquakes and underground detonations.

On the Detectability of Synthetic Disturbances in FG5 Absolute Gravimetry Data Using Lomb-Scargle Analysis

GEOMATICA ◽  
2012 ◽  
Vol 66 (2) ◽  
pp. 113-124 ◽  
Author(s):  
Martin Orlob ◽  
Alexander Braun
Keyword(s):  
Spectral Analysis ◽  
Signal To Noise Ratio ◽  
Sensitivity Function ◽  
Adjustment Process ◽  
Environmental Disturbance ◽  
Signal To Noise ◽  
Absolute Gravimetry ◽  
Disturbance Parameter ◽  
Periodogram Analysis ◽  
Frequency Phase

An instrumental or environmental disturbance (signal plus noise) in FG5 absolute gravimetry observations becomes visible by analyzing the residuals, which represent the misfit from the theoretical acceleration parabola. While spectral analysis of FG5 residuals via classical discrete Fourier transform (DFT) is limited by the non-equispaced nature of the FG5 observations, the Lomb-Scargle periodogram can analyze nonequispaced observations and estimate (detect) signals in FG5 residuals. We investigate the detectability of synthetically introduced disturbances in FG5 residuals using Lomb-Scargle periodogram analysis. The sensitivity of the FG5 measurement and adjustment process is a function of disturbance frequency, amplitude, phase, and signal-to-noise ratio (SNR). We conclude that the used drop length and the transfer function of the instrument can significantly alter the estimated gravity values. Further, we establish a sensitivity function called LOFSMAP which depends on the disturbance parameter space of amplitude, frequency, phase and SNR.

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