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  • 1
    Digitale Medien
    Digitale Medien
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 46 (1942), S. 528-533 
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 6602-6604 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have investigated the low-frequency noise and effective flux sensing area of a field cooled dc superconducting quantum interference device magnetometer from YBa2Cu3O7 in magnetic fields up to 200 μT, both before and after it was patterned with holes to reduce the maximum structural width of the pickup loop. We find that even in low fields the noise of the unpatterned magnetometer steadily increases with the applied field. However, after the patterning for the holes, the noise remains at the zero field level up to a threshold field of 35 μT and is always less than in the unpatterned case. This threshold field is also found in field dependent measurements of the total harmonic distortion. The effective area of the magnetometer depends on the cooling field, and the dependence is different in the unpatterned and the patterned case. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 31 (1983), S. 0 
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 22 (1974), S. 0 
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 5
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 18 (1970), S. 0 
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 9 (1961), S. 0 
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 2 (1954), S. 0 
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 22 (1974), S. 0 
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 28 (1980), S. 0 
    ISSN: 1365-2478
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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