NOTES ON MULTIPLE REFLECTIONS

Geophysics ◽  
1948 ◽  
Vol 13 (1) ◽  
pp. 55-56
Author(s):  
Dean Walling
Keyword(s):  
Multiple Reflection ◽  
Large Percentage ◽  
Multiple Reflections ◽  
Reflection Theory ◽  
Proper Interpretation

Since the inception of the reflection seismograph, apparent reflections have been observed from time to time, which for one reason or another, do not meet the requirements of normal reflections from interfaces in the sedimentary section. Various theories have served to explain and allow the proper interpretation of a large percentage of these spurious energies. Among these is the multiple‐reflection theory which has proven to be applicable in many cases.

scholarly journals Data-driven internal multiple elimination and its consequences for imaging: A comparison of strategies

Geophysics ◽  
2019 ◽  
Vol 84 (5) ◽  
pp. S365-S372 ◽  
Author(s):  
Lele Zhang ◽  
Jan Thorbecke ◽  
Kees Wapenaar ◽  
Evert Slob
Keyword(s):  
Inverse Scattering ◽  
Computational Cost ◽  
Multiple Reflection ◽  
Data Driven ◽  
Transmission Losses ◽  
Multiple Reflections ◽  
Data Set ◽  
Numerical Examples ◽  
Inverse Scattering Series ◽  
Multiple Elimination

We have compared three data-driven internal multiple reflection elimination schemes derived from the Marchenko equations and inverse scattering series (ISS). The two schemes derived from Marchenko equations are similar but use different truncation operators. The first scheme creates a new data set without internal multiple reflections. The second scheme does the same and compensates for transmission losses in the primary reflections. The scheme derived from ISS is equal to the result after the first iteration of the first Marchenko-based scheme. It can attenuate internal multiple reflections with residuals. We evaluate the success of these schemes with 2D numerical examples. It is shown that Marchenko-based data-driven schemes are relatively more robust for internal multiple reflection elimination at a higher computational cost.

Multiple Reflection Effect on Spin-Transfer Torque Dynamics in Spin Valves with a Single or Dual Polarizer

SPIN ◽  
2015 ◽  
Vol 05 (01) ◽  
pp. 1550003 ◽  
Author(s):  
Weiwei Zhu ◽  
Zongzhi Zhang ◽  
Jianwei Zhang ◽  
Yaowen Liu
Keyword(s):  
Spin Valve ◽  
Spin Transfer Torque ◽  
Multiple Reflection ◽  
Spin Transfer ◽  
Reflection Effect ◽  
Multiple Reflections ◽  
Applied Current ◽  
Negative Current ◽  
Ferromagnetic Layers ◽  
Scattering Matrix Method

In this paper, spin-dependent multiple reflection effect on spin-transfer torque (STT) has been theoretically and numerically studied in a spin valve nanopillar with a single or dual spin-polarizer. By using a scattering matrix method, we formulate an analytical expression of STT that contains the multiple interfacial reflection effect. It is found that the multiple reflections could enhance the STT efficiency and reduce the critical switching current. The STT efficiency depends on the spin polarization of both the free layer and polarizer. In the nanopillars with a dual spin polarizer, the multiple reflections would cause an asymmetric frequency dependence on the applied current, albeit exactly the same parameters are used in all three ferromagnetic layers, indicating that the frequency in the negative current varies much faster than that in the positive case.

SPECTRA OF WATER REVERBERATIONS FOR PRIMARY AND MULTIPLE REFLECTIONS

Geophysics ◽  
1972 ◽  
Vol 37 (5) ◽  
pp. 788-796 ◽  
Author(s):  
John Pflueger
Keyword(s):  
Reflection Coefficient ◽  
Seismic Event ◽  
Theoretical Study ◽  
Water Layer ◽  
Multiple Reflection ◽  
Multiple Reflections ◽  
Quick Method ◽  
Sea Floor ◽  
Marine Data ◽  
Amplitude Characteristics

A theoretical study shows that passage of a seismic event through the water‐layer filter imposes amplitude characteristics on the resultant reverberating event which are independent of whether the event is a primary reflection or a multiple reflection. The phase characteristics of each order of event are, however, different. It is also shown that the reverberating sequence from a multiple reflection can be “whitened” by deconvolution but will still exhibit ringing. This phenomenon explains why some marine data, containing dominantly multiple reflections, are not amenable to deringing using standard deconvolution approaches. In addition, a quick method of obtaining the approximate reflection coefficient of the sea floor is derived.

SOME EXPERIMENTS ON MULTIPLE REFLECTION CANCELLATION

Geophysics ◽  
1965 ◽  
Vol 30 (6) ◽  
pp. 1085-1093 ◽  
Author(s):  
Daniel Silverman ◽  
N. R. Sparks
Keyword(s):  
Noise Level ◽  
Multiple Reflection ◽  
Multiple Reflections ◽  
Near Surface ◽  
High Noise ◽  
Precise Information ◽  
High Noise Level ◽  
The Earth ◽  
Primary Signal ◽  
Seismic Records

One of the most promising methods of identification or cancellation of multiple reflections on seismic records involves the calculation of synthetic records with all primaries and multiples, and the matching of the synthetic record with the field record. Such matching suffers today from the lack of precise information about the velocities and densities of the formations, dips of beds nonvertical transmission, etc. One possibility of improving this match involves the use of the earth itself as the “synthetic record computer.” In this process, the upcoming (or downgoing) primary signals are fed back into the earth with a vibrator in proper amplitude and phase to create a synthetic record of multiples only, which should match the multiples on the field record. Of course, only those multiple reflections which include a downward reflection from beds above the primary signal detectors will be included in the synthetic record of multiples only. The paper reports two experimental programs. One was carried out on an analog network to simulate the near‐surface and deeper formations, with means to feed back the upcoming signals in proper timing and polarity to cancel the multiples. These experiments indicated the theoretical workability of the process. The second program of experiments involved the use of a vertical spread to detect the upcoming and downgoing signals, and the use of a hydraulic vibrator to impress those signals back into the earth. These experiments were not conclusive because of insufficient power in the vibrator and high noise level. However, they indicated possible ways in which these limitations might be reduced, and the method applied to routine field operations.

A MARINE SEISMIC MODEL

Geophysics ◽  
1956 ◽  
Vol 21 (2) ◽  
pp. 320-336 ◽  
Author(s):  
George P. Sarrafian
Keyword(s):  
Water Layer ◽  
Multiple Reflection ◽  
Air Bubbles ◽  
Seismic Model ◽  
Multiple Reflections ◽  
Marine Seismic ◽  
Search For Information

A model for the study of marine seismic phenomena is described. Study of multiple‐reflection phenomena forms the basis for the course of experiments. It is shown that the multiple‐reflection phenomenon of a disturbance with slowly decaying amplitude may be duplicated in the model. Multiple‐reflection problems are studied in which the bottom of the water layer is tilted or thin. A mass of air bubbles is shown to be of use in attenuating multiple reflections. The possible application of the marine model in a search for information about certain problems in field prospecting is suggested.

MULTIPLE‐REFLECTION EVIDENCE

Geophysics ◽  
1948 ◽  
Vol 13 (1) ◽  
pp. 41-44 ◽  
Author(s):  
Joseph C. Waterman
Keyword(s):  
San Joaquin Valley ◽  
Multiple Reflection ◽  
East Side ◽  
Multiple Reflections ◽  
Basement Complex ◽  
Well Data

A rather interesting example of multiple reflections was found in one area in Madera County on the east side of the San Joaquin Valley of California. In this region the top of the basement complex is an excellent reflecting horizon, and the determination of the depth of the basement was confirmed by well data.

IMPROVED NORMAL MOVEOUT DIFFERENCE CURVE

Geophysics ◽  
1976 ◽  
Vol 41 (5) ◽  
pp. 1048-1050
Author(s):  
Poh‐Hsi Pan
Keyword(s):  
Multiple Reflection ◽  
Multiple Reflections ◽  
Difference Curve

The normal moveout difference, or the residual normal moveout between the primary and the multiple reflections, are used in studying multiple reflection cancellation and designing effective geophone cables. Its definition was clearly described in Mayne’s paper (1962, p. 932) and referred to by Marr and Zagst (1967, p. 213).

Suppression of long‐delay multiple reflections by predictive deconvolution

Geophysics ◽  
1978 ◽  
Vol 43 (7) ◽  
pp. 1352-1367 ◽  
Author(s):  
John B. Sinton ◽  
R. W. Ward ◽  
Joel S. Watkins
Keyword(s):  
Multiple Reflection ◽  
Multiple Reflections ◽  
Seismic Section ◽  
University Of Texas ◽  
Predictive Deconvolution ◽  
Marine Science Institute ◽  
Multiple Coverage ◽  
The University ◽  
Prediction Filter ◽  
Detailed Picture

Multiple coverage seismograms acquired in the western Gulf of Mexico during 1975 by the University of Texas Marine Science Institute contain prominent, long‐delay multiple reflections, which obscure primary reflections from deep within the earth’s crust. Predictive deconvolution operators, containing gaps of zeros with a duration of 4 to 5 sec, proved effective in suppressing the long‐delay multiple reflections in these seismograms. There is a correspondence between the complexity of the long‐delay multiple reflection and the length of the optimal prediction filter, with the more complex multiple reflection requiring the longer prediction filter. Overall, the deconvolved reflection profiles provide an extremely detailed picture of the reflector characteristics producing both the sedimentary and deep crustal reflections. The top of oceanic layer 3, at a two‐way reflection travel of 10.1 sec in the area of this study, exhibits minor localized structure in three of the four profiles that were deconvolved. A possible Moho reflection was identified in one profile at a two‐way reflection traveltime of 11.6 sec, showing little apparent dip across the entire seismic section.

Two‐dimensional induction log modeling using a coupled‐mode, multiple‐reflection series method

Geophysics ◽  
1993 ◽  
Vol 58 (4) ◽  
pp. 466-474 ◽  
Author(s):  
David M. Pai ◽  
J. Ahmad ◽  
W. David Kennedy
Keyword(s):  
Separation Of Variables ◽  
Expansion Method ◽  
Multiple Reflection ◽  
Two Dimensional ◽  
Multiple Reflections ◽  
Vertical Coordinate ◽  
Modal Expansion ◽  
Coupled Mode ◽  
Modal Expansion Method ◽  
Method Of Solution

In induction logging, both vertical and radial conductivity variations exist in the logged medium; elementary separation of variables cannot be applied directly to the partial differential equation describing the electromagnetic field in such a medium. A modal expansion method of solution can be designed using modes defined with respect to the vertical coordinate. This method breaks the original two‐dimensional (2-D) problem into a set of independent one‐dimensional (1-D) problems. The receiver signal is decomposed into a direct signal traveling within the borehole and a reflection signal bearing information about the conductivity distribution outside the borehole. The solution is obtained as a coupled‐mode, multiple‐reflection series accounting for repeated mode reflections at the vertical boundaries in the medium. Each term in the series represents the next higher order reflection in a sequence of multiple reflections; results show two terms are sufficient to reach accuracy acceptable for log modeling.

MULTIPLE REFLECTION PROBLEMS IN WESTERN CANADA

Geophysics ◽  
1963 ◽  
Vol 28 (5) ◽  
pp. 882-893 ◽  
Author(s):  
Stanley A. Mouritsen
Keyword(s):  
Cross Sections ◽  
Multiple Reflection ◽  
The Other ◽  
Western Canada ◽  
Multiple Reflections ◽  
Oil Companies ◽  
Reef Structure ◽  
Seismic Records

The purpose of this paper is to stimulate interest in the problems of sedimentary multiple reflections in Canada and to show examples of some of the existing types. The types considered are: Second White Specks to the Paleozoic surface, the Blairmore to the Paleozoic surface, the suspected Ireton or base of the Nisku to the Paleozoic surface, the Devonian to the Paleozoic surface, and the base‐of‐weathering to the Paleozoic surface. Record examples were contributed by oil companies in Calgary to illustrate the Cretaceous‐to‐Paleozoic surface and the base‐of‐weathering‐to‐Paleozoic‐surface types. Records showing the other types are classified as confidential and unavailable. The base‐of‐weathering‐to‐Paleozoic‐surface multiple is shown with supporting cross‐sections and record‐sections as well as the simple field procedure, based on known data, that can be used by the field interpretation staff to help confirm this type of multiple. The problem of correctly interpreting seismic records where multiple reflections are present is discussed, and the criteria for distinguishing between multiple anomalies and true structures (particularly reef structure) presented. The conclusions drawn from the discussion are that for most types of multiple reflection interference accurate interpretations can be made. However, multiple reflections in certain areas can make definite interpretive results impossible.

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