Phase offset indicator (POI): A study of phase shift versus offset and fluid content

Geophysics ◽  
1986 ◽  
Vol 51 (3) ◽  
pp. 679-688 ◽  
Author(s):  
B. Rafipour ◽  
E. Herrin
Keyword(s):  
Phase Shift ◽  
Theoretical Work ◽  
Linear Process ◽  
Phase Changes ◽  
Study Phase ◽  
Complex Spectrum ◽  
Angle Of Incidence ◽  
Matched Filters ◽  
Fluid Content ◽  
Saturated Medium

There is limited published experimental and theoretical work related to offset‐dependent reflection and phase changes at the interface between porous media. An appropriate relationship between seismic parameters and phase shift has not been well‐established. This investigation measures variations of phase for nonnormal incidence reflection as a function of frequency at the interface of a horizontally layered porous (perforated) medium, using a two‐dimensional Plexiglas model. In both parts of this study, phase‐matched filters (PMF) are used to analyze the data. Phase‐matched filters previously have been applied to digital records of Rayleigh waves and Love waves. The purpose of the first part of the study is to demonstrate application of the PMF process to reflected compressional waves and to use this technique in discriminating multiples from primaries. By using this linear process, the complex spectrum of the primary signal can be recovered from the multiple arrivals. The reduction of reflected compressional pulse wavelets to a zero‐phase wavelet provided a tool to examine the change in phase (and amplitude) as the wave travels through a lossy medium. The second part of the study deals with the relationship of phase shift Δϕ at an interface of a horizontally layered porous medium, as a function of fluid content, angle of incidence (offset), and frequency. The result indicates that, at midband frequency of 60 kHz, an air‐ (gas‐) saturated medium would cause a large increase in Δϕ with offset, whereas a water‐saturated medium would show less change in Δϕ with offset. The phase shift‐versus‐offset response for oil is assumed to be intermediate between the responses for gas and water.

Phase-matched filters: Application to the study of Rayleigh waves

1977 ◽  
Vol 67 (5) ◽  
pp. 1259-1275
Author(s):  
Eugene Herrin ◽  
Tom Goforth
Keyword(s):  
Rayleigh Waves ◽  
Matched Filter ◽  
Group Velocity Dispersion ◽  
Wave Train ◽  
Amplitude Spectrum ◽  
Linear Process ◽  
Complex Spectrum ◽  
Greenland Sea ◽  
Matched Filters ◽  
Novaya Zemlya

abstract Phase-matched filters are defined as a class of linear filters in which the Fourier phase of the filter is made equal to that of a given signal. An iterative technique is described which can be used to find a phase-matched filter for a particular seismic signal. The process is then applied to digital records of Rayleigh waves from a synthetic source with propagation across 55° of continental path, an earthquake in the Greenland Sea recorded in Texas, and a nuclear explosion in Novaya Zemlya recorded in New Mexico. Application of the filter allows multiple arrivals to be identified and removed and allows recovery of the complex spectrum of the primary wave train along with its apparent group-velocity dispersion curve. The amplitude spectrum of the primary signal obtained by this linear process is not contaminated by interference from multipath arrivals. The filtering process also provides significant improvement in signal-to-noise ratio, greater than a factor of four for the Greenland Sea and Novaya Zemlya events.

scholarly journals Close Frequency Pairs in Delta Scuti Stars

2002 ◽  
Vol 185 ◽  
pp. 326-327
Author(s):  
K.M. Bischof ◽  
M. Breger
Keyword(s):  
Phase Shift ◽  
Power Spectra ◽  
Phase Changes ◽  
Single Frequency ◽  
Sufficient Data ◽  
Amplitude Variability ◽  
Pulsation Mode ◽  
Delta Scuti ◽  
Close Frequency ◽  
Scuti Stars

AbstractThe power spectra of several δ Scuti stars show close peaks with similar frequencies and amplitudes. Apart from possible observational problems, this can be interpreted in terms of two separate pulsation modes with similar, close frequencies or an artifact of amplitude variability of a single pulsation mode. If sufficient data are available, it is possible to distinguish between the two hypotheses on the basis of expected systematic phase changes associated with the amplitude variations of an assumed single frequency. This phase-shift test has been applied to modes found for BI CMi. In this paper we present the evidence for one of the close frequency pairs found in this star.

Infuence of Latertal Shift on Normal Moveout of SV-Wave

2014 ◽  
Vol 488-489 ◽  
pp. 873-876
Author(s):  
An Ling Wang ◽  
Fu Ping Liu
Keyword(s):  
Time Delay ◽  
Phase Shift ◽  
Seismic Data ◽  
Critical Angle ◽  
Large Error ◽  
Lateral Shift ◽  
Angle Of Incidence ◽  
Seismic Data Processing ◽  
Group Time Delay ◽  
Group Time

Using the phase shift of reflection coefficient of SH seismic wave at the interface of strata, we derived the lateral shift and group time delay of total reflected SV-wave, given formulae of normal moveout of lateral shift, discussed the influence of lateral shift on normal moveout of SV-wave, and drawn the curves of normal moveout of lateral shift and the error of normal moveout caused by lateral shift with respect to the angle of incidence.The results show that for glancing wave or angle of incidence being near the critical angle, A large error can be caused by lateral shift; The error correction of lateral shift should be done before seismic data processing.

A second moment NMR method to study phase changes in bone

1985 ◽  
Vol 13 (1) ◽  
pp. 25-28 ◽  
Author(s):  
Anthony A. Silvidi ◽  
Stephen E. Dunn
Keyword(s):  
Phase Changes ◽  
Study Phase ◽  
Second Moment ◽  
Nmr Method

The Shift Time of Reflection Sh-Wave on an Interface of Two Media

2014 ◽  
Vol 488-489 ◽  
pp. 870-872
Author(s):  
An Ling Wang ◽  
Fu Ping Liu
Keyword(s):  
Phase Shift ◽  
Reflection Coefficient ◽  
Seismic Wave ◽  
Critical Angle ◽  
Angle Of Incidence ◽  
Sh Wave ◽  
Large Shift ◽  
Order Of Magnitude

Using the phase shift of reflection coefficient of SH seismic wave at the interface of strata, we derived the shift time of total reflected SH-wave, given formulae of shift time,The results show that for glancing wave or angle of incidence being near the critical angle, the shift time are very large. A large shift can be caused,In other angle of incidence the shift time is the same order of magnitude as the wavelength (period).

scholarly journals PHASE-ISOTROPIC CORNER REFLECTOR FOR FIBER-OPTIC CONVERTER

2018 ◽  
Vol 20 (5-6) ◽  
pp. 110-117
Author(s):  
A. S. Nikitin ◽  
A. N. Borisov
Keyword(s):  
Phase Shift ◽  
Fiber Optic ◽  
Light Signal ◽  
Fiber Sensor ◽  
Angle Of Incidence ◽  
Corner Reflector ◽  
Signal Phase ◽  
Optical Device ◽  
Film Forming

The article is devoted to the design of optical device ‒ phase isotropic corner reflector, which may find application as a mirror in the fiber-optic converter. The use of phase-isotropic elements will reduce the effect of a light signal phase shift on reflection from the mirror mounted on the end of the fiber sensor. The work analyzes the existing phase devices and suggests a device using real film-forming materials, the angle of incidence of radiation, and the materials of the prism.

The Shift Time of Refraction Sh-Wave on an Interface of Two Media

2014 ◽  
Vol 551 ◽  
pp. 583-586
Author(s):  
An Ling Wang ◽  
Fu Ping Liu
Keyword(s):  
Phase Shift ◽  
Seismic Wave ◽  
Critical Angle ◽  
Angle Of Incidence ◽  
Refraction Coefficient ◽  
Sh Wave ◽  
Large Shift ◽  
Order Of Magnitude

Using the phase shift of refraction coefficient of SH seismic wave at the interface of strata, we derived the shift time of total refraction SH-wave, given formulae of shift time,The results show that for glancing wave or angle of incidence being near the critical angle, the shift time are very large. A large shift can be caused,In other angle of incidence the shift time is the same order of magnitude as the wavelength (period).

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