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 Noise reduction with reflection supervirtual interferometry

Geophysics ◽  
2020 ◽  
Vol 85 (3) ◽  
pp. V249-V256
Author(s):  
Kai Lu ◽  
Zhaolun Liu ◽  
Sherif Hanafy ◽  
Gerard Schuster
Keyword(s):  
Noise Reduction ◽  
Field Data ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Data Set ◽  
Reflection Data ◽  
The Poor ◽  
The Earth ◽  
The Common ◽  
Noise Ratio

To image deeper portions of the earth, geophysicists must record reflection data with much greater source-receiver offsets. The problem with these data is that the signal-to-noise ratio (S/N) significantly diminishes with greater offset. In many cases, the poor S/N makes the far-offset reflections imperceptible on the shot records. To mitigate this problem, we have developed supervirtual reflection interferometry (SVI), which can be applied to far-offset reflections to significantly increase their S/N. The key idea is to select the common pair gathers where the phases of the correlated reflection arrivals differ from one another by no more than a quarter of a period so that the traces can be coherently stacked. The traces are correlated and summed together to create traces with virtual reflections, which in turn are convolved with one another and stacked to give the reflection traces with much stronger S/Ns. This is similar to refraction SVI except far-offset reflections are used instead of refractions. The theory is validated with synthetic tests where SVI is applied to far-offset reflection arrivals to significantly improve their S/N. Reflection SVI is also applied to a field data set where the reflections are too noisy to be clearly visible in the traces. After the implementation of reflection SVI, the normal moveout velocity can be accurately picked from the SVI-improved data, leading to a successful poststack migration for this data set.

scholarly journals 3D supervirtual refraction interferometry

Geophysics ◽  
2020 ◽  
Vol 85 (3) ◽  
pp. Q1-Q10 ◽  
Author(s):  
Kai Lu ◽  
Sergio Chávez-Pérez
Keyword(s):  
Field Data ◽  
Signal To Noise Ratio ◽  
Synthetic Data ◽  
Theory And Practice ◽  
Signal To Noise ◽  
Stationary Source ◽  
3D Data ◽  
First Arrival ◽  
Noise Ratio

We have developed the theory and practice of 3D supervirtual interferometry (SVI) for enhancing the signal-to-noise ratio (S/N) of refraction arrivals in 3D data. Unlike 2D SVI, 3D SVI requires an extra integration along the inline direction to compute the stationary source-receiver pairs for enhanced stacking of the refraction events. The result is a significant increase in the S/N of first arrivals in the far-offset traces. We have evaluated 3D synthetic and field data examples to demonstrate the effectiveness of the proposed method. For the synthetic data tests, SVI has extended the source-receiver offset range of pickable traces from 11 to 15 km. In the field data example, SVI has extended the source-receiver offset of traces with pickable first-arrival traveltimes from 12 km to a maximum of 18 km, and the total number of reliable traveltime picks has increased by 12%, which contributes to a deeper velocity update in the traveltime tomogram.

Iterative supervirtual refraction interferometry

Geophysics ◽  
2014 ◽  
Vol 79 (3) ◽  
pp. Q21-Q30 ◽  
Author(s):  
Ola Al-Hagan ◽  
Sherif M. Hanafy ◽  
Gerard T. Schuster
Keyword(s):  
Field Data ◽  
Signal To Noise Ratio ◽  
Major Obstacle ◽  
Signal To Noise ◽  
Empirical Results ◽  
Refraction Tomography ◽  
Interferometry Method ◽  
Noise Ratio ◽  
Offset Curve

In refraction tomography, the low signal-to-noise ratio (S/N) can be a major obstacle in picking the first-break arrivals at the far-offset receivers. To increase the S/N, we evaluated iterative supervirtual refraction interferometry (ISVI), which is an extension of the supervirtual refraction interferometry method. In this method, supervirtual traces are computed and then iteratively reused to generate supervirtual traces with a higher S/N. Our empirical results with both synthetic and field data revealed that ISVI can significantly boost up the S/N of far-offset traces. The drawback is that using refraction events from more than one refractor can introduce unacceptable artifacts into the final traveltime versus offset curve. This problem can be avoided by careful windowing of refraction events.

GROUND ROLL ATTENUATION USING ADAPTIVE SINGULAR VALUE DECOMPOSITION FILTERING IN THE F-K DOMAIN

2016 ◽  
Vol 33 (3) ◽  
Author(s):  
Danilo S. Cruz ◽  
Milton J. Porsani
Keyword(s):  
Singular Value Decomposition ◽  
Seismic Data ◽  
Signal To Noise Ratio ◽  
Singular Value ◽  
Signal To Noise ◽  
Coherent Noise ◽  
Ground Roll ◽  
Noise Ratio ◽  
Value Decomposition

ABSTRACT. The land seismic data often have low signal-to-noise ratio due, among other factors, the presence of ground roll. It is a coherent noise present in seismograms that appears as linear events... RESUMO. Os dados sísmicos terrestres geralmente apresentam baixa razão sinal-ruído devido, entre outros fatores, à presença do ground roll . Trata-se de um ruído dominado por altas amplitudes...

scholarly journals ADAPTIVE SIGNAL DECOMPOSITION AND FILTERING USING BINOMIAL FILTERS APPLIED TO THE GROUND-ROLL ATTENUATION

2016 ◽  
Vol 34 (3) ◽  
Author(s):  
Cristian D. Ariza A. ◽  
Milton J. Porsani
Keyword(s):  
Seismic Data ◽  
Adaptive Filters ◽  
Signal To Noise Ratio ◽  
Seismic Signal ◽  
Noise Signal ◽  
Signal Decomposition ◽  
Signal To Noise ◽  
Ground Roll ◽  
Noise Ratio ◽  
Adaptive Signal

ABSTRACT. The ground-roll is a type of noise normally present in land seismic data. It strongly harms the signal-to-noise ratio, and interferes in several stages of the seismic data processing, strongly affecting the final quality of the obtained seismic images...Keywords: seismic noise, signal-to-noise ratio, adaptive filters, Burg algorithm, seismic signal decomposition.  RESUMO. O ground-roll é um tipo de ruído normalmente presente nos dados sísmicos terrestres. Ele prejudica muito a razão sinal-ruído e interfere em vários est´ágios do processamento de dados sísmicos, afetando fortemente a qualidade final das imagens sísmicas obtidas...Palavras-chave: ruídos sísmicos, relação sinal-ruído, filtragem adaptativo, algoritmo de Burg, decomposição do sinal sísmico.

scholarly journals The influence of geomagnetic storms on the quality of magnetotelluric impedance

2021 ◽  
Author(s):  
Hao Chen ◽  
Hideki Mizunaga ◽  
Toshiaki Tanaka
Keyword(s):  
Geomagnetic Storm ◽  
Field Data ◽  
Geomagnetic Storms ◽  
Amplitude Ratio ◽  
Signal To Noise Ratio ◽  
Series Data ◽  
Electromagnetic Signal ◽  
Artificial Noise ◽  
Signal To Noise ◽  
Noise Ratio

Abstract Magnetotelluric field data contain natural electromagnetic signals and artificial noise sources (instrumental, anthropogenic, etc.). Not all available time-series data contain usable information of the electrical conductivity distribution at depth with a low signal-to-noise ratio. The variation of the natural electromagnetic signal increases dramatically in a strong geomagnetic storm, and the signal-to-noise ratio increases. A more reliable impedance may be obtained using the storm data in a noisy environment. Three field data observed at mid-latitude were used to investigate the effect of geomagnetic storms on MT impedance quality. We mainly combined the coherence between the electric and magnetic fields and the result of MT impedance to evaluate the MT impedance quality; we also used the polarization direction, linear coherence and amplitude ratio between the local and remote magnetic field to evaluate the data quality in the noisy environments. The case studies showed that the utilization of the data observed during the geomagnetic storm could overcome the local noise and bring a reliable impedance.

Determination of the Best Emulsion for the Microscopy of Crystals

1981 ◽  
Vol 39 ◽  
pp. 32-33
Author(s):  
David A. Grano ◽  
Kenneth H. Downing
Keyword(s):  
Spatial Frequency ◽  
Information Transfer ◽  
Signal To Noise Ratio ◽  
Experimental Situation ◽  
Photographic Emulsion ◽  
Modulation Transfer ◽  
Signal To Noise ◽  
Frequency Space ◽  
Noise Ratio

The retrieval of high-resolution information from images of biological crystals depends, in part, on the use of the correct photographic emulsion. We have been investigating the information transfer properties of twelve emulsions with a view toward 1) characterizing the emulsions by a few, measurable quantities, and 2) identifying the “best” emulsion of those we have studied for use in any given experimental situation. Because our interests lie in the examination of crystalline specimens, we've chosen to evaluate an emulsion's signal-to-noise ratio (SNR) as a function of spatial frequency and use this as our critereon for determining the best emulsion.The signal-to-noise ratio in frequency space depends on several factors. First, the signal depends on the speed of the emulsion and its modulation transfer function (MTF). By procedures outlined in, MTF's have been found for all the emulsions tested and can be fit by an analytic expression 1/(1+(S/S0)2). Figure 1 shows the experimental data and fitted curve for an emulsion with a better than average MTF. A single parameter, the spatial frequency at which the transfer falls to 50% (S0), characterizes this curve.

Experiments in Bright-Field Imaging with Hollow-Cone Illumination

1981 ◽  
Vol 39 ◽  
pp. 226-227
Author(s):  
W. Kunath ◽  
K. Weiss ◽  
E. Zeitler
Keyword(s):  
Signal To Noise Ratio ◽  
Carbon Support ◽  
Electronic System ◽  
Optic Axis ◽  
Hollow Cone ◽  
Signal To Noise ◽  
Bright Field ◽  
Noise Ratio ◽  
Single Field ◽  
Field Imaging

Bright-field images taken with axial illumination show spurious high contrast patterns which obscure details smaller than 15 ° Hollow-cone illumination (HCI), however, reduces this disturbing granulation by statistical superposition and thus improves the signal-to-noise ratio. In this presentation we report on experiments aimed at selecting the proper amount of tilt and defocus for improvement of the signal-to-noise ratio by means of direct observation of the electron images on a TV monitor.Hollow-cone illumination is implemented in our microscope (single field condenser objective, Cs = .5 mm) by an electronic system which rotates the tilted beam about the optic axis. At low rates of revolution (one turn per second or so) a circular motion of the usual granulation in the image of a carbon support film can be observed on the TV monitor. The size of the granular structures and the radius of their orbits depend on both the conical tilt and defocus.

Information capacity and bandwidth limitations in the SEM

1989 ◽  
Vol 47 ◽  
pp. 84-85
Author(s):  
D. C. Joy ◽  
R. D. Bunn
Keyword(s):  
Signal To Noise Ratio ◽  
Critical Dimension ◽  
Information Capacity ◽  
Acquisition Time ◽  
Signal To Noise ◽  
Sem Image ◽  
Probe Size ◽  
Minimum Number ◽  
Noise Ratio ◽  
Signal Channel

The information available from an SEM image is limited both by the inherent signal to noise ratio that characterizes the image and as a result of the transformations that it may undergo as it is passed through the amplifying circuits of the instrument. In applications such as Critical Dimension Metrology it is necessary to be able to quantify these limitations in order to be able to assess the likely precision of any measurement made with the microscope.The information capacity of an SEM signal, defined as the minimum number of bits needed to encode the output signal, depends on the signal to noise ratio of the image - which in turn depends on the probe size and source brightness and acquisition time per pixel - and on the efficiency of the specimen in producing the signal that is being observed. A detailed analysis of the secondary electron case shows that the information capacity C (bits/pixel) of the SEM signal channel could be written as :

Speech Reception in the Presence of Classroom Noise

1979 ◽  
Vol 10 (4) ◽  
pp. 221-230 ◽  
Author(s):  
Veronica Smyth
Keyword(s):  
Signal To Noise Ratio ◽  
Learning Processes ◽  
Speech Discrimination ◽  
Signal To Noise ◽  
Speech Reception ◽  
Monosyllabic Words ◽  
Noise Ratio

Three hundred children from five to 12 years of age were required to discriminate simple, familiar, monosyllabic words under two conditions: 1) quiet, and 2) in the presence of background classroom noise. Of the sample, 45.3% made errors in speech discrimination in the presence of background classroom noise. The effect was most marked in children younger than seven years six months. The results are discussed considering the signal-to-noise ratio and the possible effects of unwanted classroom noise on learning processes.

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