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  • 1
    Electronic Resource
    Electronic Resource
    MIGRATION IN THE PRESENCE OF A RUGGED INTERFACE WITH HIGH VELOCITY CONTRAST (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 31 (1983), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: In the western coal-mining area of Ruhrkohle AG, reflection seismic prospecting for the Carboniferous coal measures is severely impaired by structures with halokinetic features. These structures make the interface between Mesozoic and Paleozoic layers, i.e., the top of Zechstein in general, very rugged. Unfortunately the velocity contrast at this interface is very high in that area, the ratio of velocities being 1.5 to 2.0. Therefore, migration and stacking become a problem.Three types of migration are presented:〈list xml:id="l1" style="custom"〉1(f, x)-time-migration with vertical time-to-depth conversion as a second step.2Kirchhoff migration down to a level determined approximately by the highest points of the top of Paleozoics, i.e., 0.35 s, and Kirchhoff-downward continuation for all times exceeding 0.35 s. Intermediate static corrections for these latter times with subsequent (f, k)-time-migration and final vertical time-to-depth conversion.3Direct depth migration in the (f, x)-domain using three interval velocities.In all cases an intermediate picking of the velocity interfaces is necessary. In case 2 this occurs at an earlier stage of the process than in case 1, and in case 3 at a still earlier stage.The results of the second and third migration procedures are superior to those of the first. Possibilities for misinterpretation of faults are reduced considerably when the second or third migration procedure is applied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1983.tb01072.x
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  • 2
    Electronic Resource
    Electronic Resource
    CANCELLING MULTIPLE REFLECTIONS BY FEEDBACK (1974)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 22 (1974), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: For horizontal layering and plane horizontal impulsive wavefronts it is theoretically possible to get rid of multiple reflections by a feedback procedure which can easily be derived using raypath philosophy. To reduce the increase of noise inherent in the method the precise theoretical formulae are altered in such a manner that a practical application becomes possible. For this purpose the autocorrelation will be used.Application of the new process to a CRP section where the shot geophone distances in the field had not been long enough to attenuate multiple reflections effectively gave favourable results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1974.tb00109.x
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  • 3
    Electronic Resource
    Electronic Resource
    COMPUTATION OF INTERVAL VELOCITIES FROM COMMON REFLECTION POINT MOVEOUT TIMES FOR n LAYERS WITH ARBITRARY DIPS AND CURVATURES IN THREE DIMENSIONS WHEN ASSUMING SMALL SHOT-GEOPHONE DISTANCES (1976)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 24 (1976), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: It is well known that interval velocities can be determined from common-reflection-point moveout times. However, the mathematics becomes complicated in the general case of n homogeneous layers with curved interfaces dipping in three dimensions.In this paper the problem is solved by mathematical induction using the second power terms only of the Taylor series which represents the moveout time as a function of the coordinate differences between shot and geophone points. Moreover, the zero-offset reflection times of the nth interface in a certain area surrounding the point of interest have to be known. The n—I upper interfaces and interval velocities are known too on account of the mathematical induction method applied. Thus, the zero-offset reflection raypath of the nth interface can be supposed to be known down to the intersection with the (n—1)th interface.The method applied consists mainly in transforming the second power terms of the moveout time from one interface to the next one. This is accomplished by matrix algebra.Some special cases are discussed as e.g. uniform strike and small curvatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1976.tb00387.x
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  • 4
    Electronic Resource
    Electronic Resource
    APPLICATION OF REFRACTION SEISMICS TO SUBSALT TECTONIC PROBLEMS IN A DEEP SALTDOME BASIN (1970)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 18 (1970), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Despite the use of CDP and digital methods the Zechstein base is still the deepest horizon in the vast salt-dome basin of Central Europe for which continuous information can be obtained by reflection seismics. Thus in North-western Germany, in addition to reflection seismics, the refraction seismic method has been increasingly used for a reliable survey of deeper horizons.The first part of the paper deals with the investigation of the various possibilities and limitations of refraction seismics with regard to the investigation of Pre-Zechstein layers in a basin with a tectonically very complicated overburden. The recording techniques specially developed for continuous profiling of the desired refraction seismic arrivals and the data processing methods are described.The main problems of interpretation are then discussed, in particular with regard to depth representation. The advantages and disadvantages of the various methods, e.g. Gardner's, Hales' and Wyrobek's, and of the wave-front method, are compared. On account of the tectonically complicated overburden Thornburgh's wave-front method proved to be the most useful.In a further section the various possibilities for velocity determinations are mentioned, e.g. Wyrobek's determination of the overburden velocity, for which the wave-front method automatically furnishes the necessary corrections to a deep datum.Finally, some examples are given for the results obtained, including some incidental information on the deeper crust.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1970.tb02118.x
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  • 5
    Electronic Resource
    Electronic Resource
    REFLEXION UND BRECHUNG BEIM SCHRÄGEN DURCHGANG EBENER SEISMISGHER WELLEN DURCH N PLANPARALLELE MEDIEN (1961)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 9 (1961), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1961.tb01509.x
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  • 6
    Electronic Resource
    Electronic Resource
    EXTENSION TO THREEDIMENSIONAL PROBLEMS CONCERNING AN APPROXIMATE CORRECTION METHOD FOR REFRACTION IN REFLECTION SEISMIC PROSPECTING (1954)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 2 (1954), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: The formulas derived by the author in a preliminary paper for taking into consideration refraction when dealing with the problem of a vertical plane are extended to the three-dimensional case. Vector analysis is extensively applied. Among others it is shown that in the general case the 3 horizontal twodimensional vectors, i.e.〈list xml:id="l1" style="custom"〉1) the gradient of the time of reflection2) the direction of true dip3) the vector from the shot point to the projection of the reflecting point, point into 3 different directions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1954.tb01280.x
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  • 7
    Electronic Resource
    Electronic Resource
    NEW POSSIBILITIES FOR REFLECTION SEISMICS BY UNDERSHOOTING BODIES WITH COMPLICATED TECTONICS (1974)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 22 (1974), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: In modern oil exploration layers of prospective interest with rather simple structural features are often overlain by very complicated bodies as e.g. saltdomes or other kinds of diapirs, olistostromes, or front zones of overthrusted blankets. In all these cases normal reflection seismic investigations, where downgoing and upgoing rays are rather close to each other, mostly fail, either because no reflections from underneath the complicated bodies are obtained, or because a reliable migrated depth presentation becomes practically impossible due to the inhomogeneity of the overlying bodies.The undershooting technique avoids these difficulties by using ray paths which do not traverse the complicated bodies e.g. by shooting on one side of a saltdome and recording on the other side. On account of the large shot-geophone distances in this method special considerations and computer processes were developed concerning moveout corrections for common depth point stacking and migrated depth presentation.In many cases the location of the disturbing complicated bodies is known in advance. The shooting and recording program can then be adjusted to this knowledge and thereby kept to a minimum. If the location of the complicated bodies is unknown a more extended seismic program has to be carried out encompassing a great variety of shot-geophone distances. But in this case the approximate location of the complicated bodies can be deduced from the survey too.Results are presented in order to give an idea of the efficiency of the new seismic tool.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1974.tb00062.x
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  • 8
    Electronic Resource
    Electronic Resource
    MAPPING NON-REFLECTING VELOCITY INTERFACES BY NORMAL MOVEOUT VELOCITIES OF UNDERLYING HORIZONS (1980)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 28 (1980), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: The normal moveout velocity of a reflecting bed is a function of the dips and curvatures of all overlying velocity interfaces. Now let the (N– 1)th velocity interface be a non- (or badly) reflecting bed, whereas the other interfaces, including the base of the Nth layer, reflect satisfactorily, and let the velocities UN– 1 and UN of the (N– 1)th and Nth layer, respectively, be known. Then the normal moveout velocity for the base of the Nth layer, if known in one direction at a certain part of the surface of the earth, provides a second order differential equation in the horizontal coordinates x and y for the depth ZN – 1(x, y) of the unknown interface.The mathematics becomes rather simple in the case of two-dimensional geological structures. For this case and N= 2 the differential equation mentioned can be solved by stepwise integration or by iteration. One of the many possible applications of the new concept is the determination of the structure of the base of an overthrusting sheet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1980.tb01231.x
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  • 9
    Electronic Resource
    Electronic Resource
    A THEOREM CONCERNING ANISOTROPY OF STRATIFIED MEDIA AND ITS SIGNIFICANCE FOR REFLECTION SEISMICS (1956)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 4 (1956), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: It is proved that horizontally stratified media, the various materials of which do not differ in their Poisson number, can be considered as isotropic for reflections of a small dip when taking into account quasi-longitudinal waves which have to be reckoned with in practice. Approximating the surface of the wave by an ellipsoid would, however, result in considerable errors.Moreover, curves are presented allowing practical calculations for steeper dips to be made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1956.tb01411.x
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  • 10
    Electronic Resource
    Electronic Resource
    COMBISWEEP—A CONTRIBUTION TO SWEEP TECHNIQUES (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 27 (1979), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Nonlinear sweeps have often successfully been employed in the 1960s. However, this area of sweep technology has been neglected since the introduction of digital recording techniques in the Vibroseis system. Now the advent of computerized recording instruments yields a new economical possibility of forming approximately nonlinear sweeps by combining several linear sweeps with or without time gaps to a “Combisweep”. The total duration of a Combisweep may be as long as the maximum available recording time, for example 32 s.Beside the attenuation of correlation noise, the new method has further merits, such as the weighting of predetermined frequency ranges, in order to effect a certain kind of optimum filtering on the emitter side, or in order to compensate to some degree for frequency dependent absorption.In all these applications the Combisweep is considered as one signal in the correlation process. But by correlating with the individual sweeps or a partial combination of them and by applying automatic switching at predetermined times within the gaps between the individual sweeps additional possibilities arise, such as obtaining in one run with a twenty-four channel recording unit twenty-four traces with small distances between vibrators and geophones for shallow reflections and another twenty-four traces with larger distances for deeper reflections. Various Combisweeps and their applications are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1979.tb00960.x
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