THE POTENTIAL OF DIGITAL SEISMIC RECORDINGS FOR MULTICHANNEL PROCESSING

Geophysics ◽  
1970 ◽  
Vol 35 (3) ◽  
pp. 461-470 ◽  
Author(s):  
J. P. Lindsey
Keyword(s):  
Dynamic Range ◽  
Single Channel ◽  
Recording Equipment ◽  
Field Equipment ◽  
Reflection Data ◽  
Field Recording ◽  
Amplifier Gain ◽  
Multichannel Processing ◽  
New Processing ◽  
Processing Techniques

The availability of seismic digital field recording equipment has made possible new processing techniques which achieve significant reflection data enhancement. Typical of the processes that are now used routinely are deconvolution, autocorrelation and crosscorrelation, Fourier transformation, and spectral alteration. A recording fidelity that reduces errors to 1 part in 10,000 has provided the motive for developing and using these techniques. An additional capability of digital field equipment is the recording of amplifier gain information to a precision of 0.1 percent. This appears to provide a motive for developing multichannel processes which expand further our processing capabilities beyond the essentially single channel ones now in use. The present study evaluates the multichannel processing potential afforded by present day seismic digital field recording systems. The evaluation is based on measurement and computation of the effects of channel performance deviations. Each component of the field recording system (geophone, cable, amplifier, filters, sampling skew) separately, and the system as a whole, are evaluated in this context. Results of the study indicate that whereas any given channel possesses a dynamic range of 80 db, channel‐to‐channel variations establish a dynamic range of only 15 db. The 15 db range sets a serious limit on the performance of multichannel processes and points up the need for additional improvements in field hardware capabilities.

New Processing Techniques in Ultrasound Imaging Systems

1982 ◽  
pp. 177-193 ◽  
Author(s):  
G. F. Manes ◽  
C. Susini ◽  
P. Tortoli ◽  
C. Atzeni
Keyword(s):  
Ultrasound Imaging ◽  
Imaging Systems ◽  
New Processing ◽  
Processing Techniques

Effect of hydrophone arrays on offshore Texas seismic signals

Geophysics ◽  
1978 ◽  
Vol 43 (6) ◽  
pp. 1083-1098
Author(s):  
M. E. Arnold
Keyword(s):  
Dynamic Range ◽  
High Amplitude ◽  
Early Event ◽  
Seismic Signals ◽  
Multiple Reflections ◽  
Surface Reflection ◽  
Field Recording ◽  
First Arrival ◽  
Slope Line ◽  
Water Bottom

The effect of hydrophone arrays in the recording of seismic signals during offshore Texas seismic marine experiments is judged by comparing traces of spatially tapered hydrophone array signals with traces that are combinations of simultaneously recorded wavetest hydrophone signals. Each spatially tapered hydrophone group array consists of 26 hydrophones nonuniformly spaced over 212 ft. The wavetest streamer section consists of 36 groups of two hydrophones, each pair connected in parallel and with hydrophones back‐to‐back for acceleration cancellation, with 5-ft spacing between groups. Reflection from deep subsurface interfaces are negligibly affected by hydrophone arrays except for very long arrays and/or long‐range distances. Consequently, the report is primarily concerned with the effects of simulated and real hydrophone arrays on first‐arrival signal and early subbottom reflections. Comparison of theoretical and actual seismic traces from an Aquapulse source for near range distances (835 ft) used in normal operations indicates that (1) near‐simultaneous arrival of the direct wave and surface reflection result in their virtual cancellation, (2) the early event with largest amplitude is associated with constructive interference between source and receiver ghost reflections, and (3) the “pseudo‐bubble” period effectively fixed the predominant frequency of all seismic events at values near 28 Hz. At medium range distances (4755 ft), such comparisons indicate that (1) first arrivals are refracted waves traveling in subbottom layers; (2) the water‐bottom reflection is beyond critical angle and is, therefore, complex; (3) the early events with largest amplitude are multiple reflections; and (4) at least two orders of water‐bottom multiples are identified. The attenuation of the high‐amplitude, first‐arrival signal that includes the water‐bottom reflection permits greater dynamic range in field recording and higher levels of “true” amplitude for later reflections without overload distortion of early events on playback. However, if improved resolution of reflection from moderate depths (∼4000 ft) is important, then arrays of length studied in this report (∼200 ft) should not be used to record signals at range distances greater than about 2000 ft because frequencies above 50 Hz are attenuated severely. Spectral analysis of wavetest records in the absence of signals shows that the wavenumber distribution of the noise is located along a slope line equivalent to 5000 ft/sec between wavenumbers that imply a spectral distribution of 30 to 100 Hz. Theoretical array response studies show that both the 36‐element Chebyshev array and the 26‐element spatially tapered array are superior to a 36‐element uniformly weighted array in rejection of seismic noise in the spectral range of 30 to 100 Hz.

ROLL‐ALONG AND DROP‐ALONG SEISMIC TECHNIQUES

Geophysics ◽  
1963 ◽  
Vol 28 (5) ◽  
pp. 831-841
Author(s):  
Lorenz Shock
Keyword(s):  
Data Processing ◽  
Field Data ◽  
Shooting Method ◽  
Quality Of Data ◽  
Recording Equipment ◽  
Standard Pattern ◽  
Field Recording ◽  
Weight Drop ◽  
Associated Data

The designation “Roll‐Along” is used to indicate the use of horizontal‐data‐stacking techniques when field data are derived by the shooting method. The term “Drop‐Along” is used for weight‐drop data. These methods have proven valuable in obtaining usable data in areas where the standard pattern techniques are ineffective, or where extreme multiplicity requirements make patterns economically impractical. Operational techniques have been developed for both Roll‐Along and Drop‐Along in which standard field recording equipment and cables are utilized. A discussion of these techniques and the associated data processing operations is presented. Record‐sections are used to illustrate the quality of data obtainable by these methods and to compare it to pattern shooting.

Wide-area imaging from OBS multiples

Geophysics ◽  
2009 ◽  
Vol 74 (6) ◽  
pp. Q41-Q47 ◽  
Author(s):  
Ranjan Dash ◽  
George Spence ◽  
Roy Hyndman ◽  
Sergio Grion ◽  
Yi Wang ◽  
...  
Keyword(s):  
Single Channel ◽  
Water Layer ◽  
Velocity Model ◽  
Imaging Method ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
Conventional Imaging ◽  
Depth Migration ◽  
Reflection Data ◽  
Obs Data

The subseafloor structure offshore western Canada was imaged using first-order water-layer multiples from ocean-bottom seismometer (OBS) data and the results were compared to conventional imaging using primary reflections. This multiple-migration (mirror-imaging) method uses the downgoing pressure wavefield just above the seafloor, which is devoid of any primary reflections but consists of receiver-side ghosts of these primary reflections. The mirror-imaging method employs a primaries-only Kirchhoff prestack depth migration algorithm to image the receiver ghosts. The additional travel path of the multiples through the water layer is accounted for by a simple manipulation of the velocity model and processing datum: the receivers lie not on the seabed but on a sea surface twice as high as the true water column. Migration results show that the multiple-migrated image provides a much broader illumination of the subsurface than is possible for conventional imaging using the primaries, especially for the very shallow reflections and sparse OBS spacing. The resulting image from mirror imaging has illumination comparable to the vertical incidence surface streamer (single-channel) reflection data.

An automated approach to classification of duplex assay for digital droplet PCR

2018 ◽  
Vol 16 (03) ◽  
pp. 1850003 ◽  
Author(s):  
Cong Liu ◽  
Wuping Zhou ◽  
Tao Zhang ◽  
Keming Jiang ◽  
Haiwen Li ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Single Channel ◽  
Generalized Pareto Distribution ◽  
Automated Classification ◽  
Factors Affecting ◽  
Generalized Pareto ◽  
Droplet Pcr ◽  
The Right ◽  
Digital Polymerase Chain Reaction

In the digital polymerase chain reaction (dPCR) detection process, discriminating positive droplets from negative ones directly affects the final concentration and is one of the most important factors affecting accuracy. Current automated classification methods usually discuss single-channel detections, whereas duplex detection experiments are less discussed. In this paper, we designed a classification method by estimating the upper limit of the negative droplets. The right tail of the negative droplets is approximated using a generalized Pareto distribution. Furthermore, our method takes fluorescence compensation in duplex assays into account. We also demonstrate the method on Bio-Rad’s mutant detection dataset. Experimental results show that the method provides similar or better accuracy than other algorithms reported over a wider dynamic range.

High dynamic range single channel sampling of wideband RF signals using ultra‐fast nanoscale photoconductive switching

2016 ◽  
Vol 52 (3) ◽  
pp. 237-239 ◽  
Author(s):  
C. Tripon‐Canseliet ◽  
M. Zegaoui ◽  
G. Jestin ◽  
C. Coinon ◽  
P. Berger ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Single Channel ◽  
High Dynamic Range ◽  
Rf Signals ◽  
Photoconductive Switching ◽  
High Dynamic

New Processing Techniques for the Creation of Micro-Opto-Mechanical Machines and Photonic Devices Embedded in Glass

2002 ◽  
Vol 739 ◽  
Author(s):  
Meg Abraham ◽  
Peter Fuqua ◽  
David P. Taylor ◽  
William W. Hansen ◽  
Henry Helvajian ◽  
...  
Keyword(s):  
Silver Halide ◽  
Three Dimensional ◽  
Direct Write ◽  
Buried Structures ◽  
Nucleation Sites ◽  
New Processing ◽  
Meta Silicate ◽  
Processing Techniques ◽  
Aerospace Corporation ◽  
Nano Wires

ABSTRACTThe use of lasers to create intricate three-dimensional and buried structures [1] in photostructural glass has been well demonstrated at The Aerospace Corporation over the past four years. In these instances the glass used (Foturan™, made by the Schott Group) forms a silver nucleation sites on exposure to intense UV laser light via a two-photon process. Subsequent annealing causes a localized crystal growth to form a meta-silicate phase which can be etched in dilute hydrofluoric acid at rates of 20 to 50 times that of the unprocessed glass. We are now in the process of experimenting with another formulation of photosensitive glass, also pioneered by Corning Glass Works, that behaves differently during the bake process. In the second case, a photoexposure and bake process creates a silver-halide crystal and forms an adjacent void in the glass. A second photoexposure and bake allows for the migration of more silver into the void creating patterned formations of silver nano-wires [2]. Recent experiments with this type of glass have shown that the manipulation of the size and density of the embedded nano-wires as well as the overall pattern of the clusters can be controlled using direct-write exposure to laser processing.

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