A Seismic Reflection Model of the Crust near Edmonton, Alberta

1974 ◽  
Vol 11 (1) ◽  
pp. 101-109 ◽  
Author(s):  
D. C. Ganley ◽  
G. L. Cumming
Keyword(s):  
Seismic Reflection ◽  
Average Velocity ◽  
Velocity Spectrum ◽  
Common Depth Point ◽  
Reflection Model ◽  
Southern Alberta ◽  
Seismic Records ◽  
Point Data ◽  
Lowermost Portion

Reflection profiles shot about 10 km north of the Edmonton seismic observatory (EDM) indicate dips within the crust of 15 to 20° southeast, with a prominent reflecting horizon at 20 km apparently being offset 4 km by a fault. The average velocity in the crust to this horizon is 6.3–6.4 km/s. Deeper reflections tentatively correlated with the "Riel" discontinuity mapped in southern Alberta indicate a velocity in a second layer of 6.5 km/s to a depth of 32 km, with the base of the crust being essentially horizontal at 35.5 km. The lowermost portion of the crust appears to be significantly thinner here than in southern Alberta, although the general features of the seismic records appear similar in both locations.Velocities are determined by a modified version of the velocity spectrum technique, which does not require common depth point data.

NOISE ATTENUATION ON COMMON‐DEPTH‐POINT SEISMIC RECORDS BY A SEMIDETERMINISTIC APPROACH

Geophysics ◽  
1968 ◽  
Vol 33 (5) ◽  
pp. 723-733 ◽  
Author(s):  
John C. Robinson
Keyword(s):  
Frequency Domain ◽  
Random Noise ◽  
Analytic Solutions ◽  
Harmonic Spectrum ◽  
Algebraic Equations ◽  
Coherent Noise ◽  
Common Depth Point ◽  
Seismic Records ◽  
Point Data ◽  
The Time Domain

A simple seismic record synthesis for common‐depth‐point data was examined for analytic representation in terms of its harmonic spectrum. This frequency‐domain investigation revealed that the primary‐reflection signal can be completely recovered in the absence of random noise, or it can be better recovered in the presence of random noise than normal stacking affords, especially, if the coherent‐noise‐to‐random‐noise ratio is high. The success of this technique is founded upon the principle that difference equations in the time domain become algebraic equations in the frequency domain. The technique is partially “probabilistic” because analytic solutions for the primary‐reflection signal are stacked for further attenuation of noise. The constituents of the seismic records, after static and normal‐moveout corrections, are: identical, coincident, primary‐reflection signal; identical, time‐shifted coherent noise; and random noise. The coherent‐noise time shifts must be determined for application of the semideterministic technique; methods are discussed in the Data Processing section.

Decomposition (DECOM) approach applied to wave field analysis with seismic reflection records

Geophysics ◽  
1982 ◽  
Vol 47 (6) ◽  
pp. 869-883 ◽  
Author(s):  
Jisoo V. Ryu
Keyword(s):  
Frequency Response ◽  
Wave Field ◽  
Seismic Reflection ◽  
Space Time ◽  
The Other ◽  
Field Analysis ◽  
Velocity Spectrum ◽  
Decomposition Approach ◽  
Wavenumber Domain ◽  
Common Depth Point

Seismic common‐depth‐point (CDP) gathered data contain waves of various reflection phases other than the primary events of interest. Such waves often form distinctive, separate peaks in the velocity spectrum derived from the CDP gather, and their propagation modes can often be identified. To exploit such separation and identification, a method is developed to decompose the CDP‐gathered data into several phases. The method combines normal moveout (NMO) removal, space‐time filtering, and NMO restoration. The space‐time operator central to this method is shown to have several useful properties. Its frequency response passes one quadrant pair in the frequency‐wavenumber domain and rejects the other. A set of marine reflection records is used to demonstrate the usefulness of the decomposition approach, particularly for separating primary from nonprimary waves, and waves of possible marine PSSP mode from all others. Both examples may bear some exploration significance.

Common-depth-point seismic-reflection survey on the Mississippi River in the vicinity of Alton, Illinois

1984 ◽  
Author(s):  
G.B. Tirey ◽  
R.A. Wise ◽  
E.A. Winget
Keyword(s):  
Mississippi River ◽  
Seismic Reflection ◽  
Common Depth Point

Results of a seismic reflection survey across the fault zone between the Thompson nickel belt and the Churchill Tectonic Province, northern Manitoba

1981 ◽  
Vol 18 (1) ◽  
pp. 13-25 ◽  
Author(s):  
A. G. Green
Keyword(s):  
Fault Zone ◽  
Lower Crust ◽  
Seismic Reflection ◽  
High Amplitude ◽  
Small Scale ◽  
Upper Crust ◽  
Travel Times ◽  
Reflection Point ◽  
Point Data ◽  
Amplitude Reflection

Approximately 11 km of four-fold common reflection point data have been recorded across a region that spans the contact fault zone between the Thompson nickel belt and the Churchill Tectonic Province. From these data it is shown that the upper crust in this region and, to a lesser extent, the lower crust are characterized by numerous scattered events that originate from relatively small-scale features. Within the Thompson nickel belt two extensive and particularly high-amplitude reflection zones, at two-way travel times of t = 5.0–5.5 s and t = 6.0–6.5 s, are recorded with apparent northwesterly dips of 0–20 °C. These reflection zones, which have a laminated character, are truncated close to the faulted contact with the Churchill Province. Both the contact fault zone and the Churchill Province in this region have crustal sections that are relatively devoid of significant reflectors. The evidence presented here confirms that the crustal section of the Thompson nickel belt is fundamentally different from that of the Churchill Tectonic Province.

AN APPROACH TO INVERSE FILTERING OF NEAR‐SURFACE LAYER EFFECTS FROM SEISMIC RECORDS

Geophysics ◽  
1961 ◽  
Vol 26 (6) ◽  
pp. 754-760 ◽  
Author(s):  
Pierre L. Goupillaud
Keyword(s):  
Surface Layer ◽  
Seismic Reflection ◽  
Normal Incidence ◽  
Resolving Power ◽  
Surface Velocity ◽  
Inverse Filtering ◽  
Near Surface ◽  
Seismic Records ◽  
Stratification Variable ◽  
Velocity Information

This paper suggests a scheme for compensating the effects that the near‐surface stratification, variable from spread to spread, produces on both the character and the timing of the seismic traces. For this purpose, accurate near‐surface velocity information is mandatory. This scheme should greatly reduce the correlation difficulties so frequently encountered in many areas. It may also be used to enhance the resolving power of the seismic reflection technique. The approach presented here is based on the rather restrictive assumptions of normal incidence, parallel equispaced plant reflectors, and noiseless conditions.

Near‐surface faulting effects on seismic reflection times

Geophysics ◽  
1983 ◽  
Vol 48 (8) ◽  
pp. 1140-1142 ◽  
Author(s):  
W. Honeyman
Keyword(s):  
Seismic Reflection ◽  
Small Time ◽  
Time Curve ◽  
Near Surface ◽  
Common Depth Point ◽  
Offset Distance ◽  
Large Spread ◽  
Offset Time ◽  
Seismic Sections ◽  
Zero Offset

The depth conversion of seismic reflection records has been the subject of many papers, particularly where faults or other geologic features are present. The common‐depth‐point (CDP) stacked seismic sections with large spread lengths of the order of 2 km have resulted in different interpretation problems. Al‐Chalabi (1979) considered the effect on stacking velocities of subsurface inhomogeneities where different rays in the CDP gather do not penetrate the same type of earth column. He showed that small time delays of 10 msec produce steps in the hyperbolic offset distance‐time curve of the CDP gather and produce stacking velocity variations of the order of ten percent. Levin (1973) considered a time delay in only one ray of the CDP gather and its effect on both stacking velocity and the zero‐offset time [Formula: see text]. This paper models the effect of near‐surface faults on the zero‐offset time [Formula: see text] of deeper layers as determined by the CDP method. This is particularly important since the zero‐offset time is plotted on the processed final record.

Distribution of magma beneath the East Pacific Rise between the Clipperton Transform and the 9°17′N Deval from forward modeling of common depth point data

1993 ◽  
Vol 98 (B8) ◽  
pp. 13945-13969 ◽  
Author(s):  
Graham M. Kent ◽  
Alistair J. Harding ◽  
John A. Orcutt
Keyword(s):  
East Pacific Rise ◽  
Forward Modeling ◽  
Common Depth Point ◽  
East Pacific ◽  
Point Data

scholarly journals PENAFSIRAN GEOLOGI PERAIRAN PULAU MENJANGAN-BALI DARI DATA SEISMIK

2016 ◽  
Vol 2 (3) ◽  
Author(s):  
Lukman Arifin ◽  
Delyuzar Ilahude
Keyword(s):  
Seismic Reflection ◽  
Active Faults ◽  
Geological Condition ◽  
Sea Floor ◽  
Marine Tourism ◽  
Shallow Seismic ◽  
Floor Surface ◽  
Seismic Records

Hasil penafsiran rekaman seismik pantul dangkal menunjukkan adanya sesar-sesar aktif di bagian barat dan bagian timur daerah selidikan. Diduga morfologi tinggian bagian timur merupakan bagian daratan Pulau Bali dan bagian barat adalah bagian daratan Pulau Jawa. Adanya onggokan di permukaan dasar laut di sekitar Tanjung Pasir Putih ditafsirkan sebagai carbonat build-up. Bentuk ini banyak ditemukan di sekitar Pulau Menjangan. yang merupakan kawasan wisata bawah laut. Kondisi geologi dari penafsiran rekaman seismik ini diharapkan dapat merupakan masukan untuk pengembangan pembangunan di kawasan wisata Pulau Menjangan. Results of shallow seismic reflection interpretation records show the present of active faults in the western and eastern part of the study area. The morphological hight in the western part is suggested as part of the Bali island and the western part is of Java island. The height at the sea floor surface around Tanjung Pasir putih is interpreted as a carbonat build-up. This form was found around the Menjangan island of marine tourism area. Geological condition interpreted from seismic records is hoped can contribute to the development of the Menjangan island tourism area.

True‐amplitude seismic migration: A comparison of three approaches

Geophysics ◽  
1997 ◽  
Vol 62 (3) ◽  
pp. 929-936 ◽  
Author(s):  
Samuel H. Gray
Keyword(s):  
Elastic Parameter ◽  
Reflection Point ◽  
Seismic Migration ◽  
Amplitude Variation With Offset ◽  
Prestack Migration ◽  
Fundamental Limitations ◽  
Common Depth Point ◽  
Seismic Records ◽  
Migration Method ◽  
Angle Dependent Reflectivity

Knowledge of elastic parameter (compressional and shear velocities and density) contrasts within the earth can yield knowledge of lithology changes. Elastic parameter contrasts manifest themselves on seismic records as angle‐dependent reflectivity. Interpretation of angle‐dependent reflectivity, or amplitude variation with offset (AVO), on unmigrated records is often hindered by the effects of common‐depth‐point smear, incorrectly specified geometrical spreading loss, source/receiver directivity, as well as other factors. It is possible to correct some of these problems by analyzing common‐reflection‐point gathers after prestack migration, provided that the migration is capable of undoing all the amplitude distortions of wave propagation between the sources and the receivers. A migration method capable of undoing such distortions and thus producing angle‐dependent reflection coefficients at analysis points in a lossless, isotropic, elastic earth is called a “true‐amplitude migration.” The principles of true‐amplitude migration are simple enough to allow several methods to be considered as “true‐amplitude.” I consider three such migration methods in this paper: one associated with Berkhout, Wapenaar, and co‐workers at Delft University; one associated with Bleistein, Cohen, and co‐workers at Colorado School of Mines and, more recently, Hubral and co‐workers at Karlsruhe University; and a third introduced by Tarantola and developed internationally by many workers. These methods differ significantly in their derivations, as well as their implementation and applicability. However, they share some fundamental similarities, including some fundamental limitations. I present and compare summaries of the three methods from a unified perspective. The objective of this comparison is to point out the similarities of these methods, as well as their relative strengths and weaknesses.

Technique for reflection prospecting in the Rub’ Al‐Khali

Geophysics ◽  
1982 ◽  
Vol 47 (8) ◽  
pp. 1135-1152 ◽  
Author(s):  
Don K. Robinson ◽  
Moujahed I. Al‐Husseini
Keyword(s):  
Average Velocity ◽  
Sand Dune ◽  
Sand Dunes ◽  
Angle Of Repose ◽  
Low Velocity ◽  
High Quality ◽  
Reflected Waves ◽  
Common Depth Point ◽  
Receiver Arrays

The Rub’ Al‐Khali desert with its extensive and massive sand dunes presents difficult technical and logistic problems for reflection prospecting. The steep angle of repose of the sand dune faces and the low velocity of the air‐filled sand cause significant delays to the reflected waves. In the dunes, in order to maintain the fidelity of both the downgoing and upcoming waves, small dynamite source and receiver arrays are each contoured to a single elevation. In the flat sabkhas, larger arrays are maintained. After application of dune statics (which are derived initially from an average velocity for the sand and then refined with residual refraction statics), the small arrays are summed so as to simulate the larger arrays used on the flat sabkhas. When the terrain is dominated by dunes, increased use of small arrays reduces the maximum spread length to the detriment of the deeper reflections. Where this occurs, a second set of dynamite patterns is fired so as to increase the effective receiver arrays from 120 to 240. In this manner the simulated spread length is maintained at a minimum of 12,000 ft. The traces resulting from the array simulation on the dunes are then gathered, along with the sabkha traces, into mixed fold common‐depth‐point (CDP) gathers and processed conventionally. This technique results in the recording of high‐quality, broadband reflection profiles with improved continuity beneath the dunes.

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