摘要:

ABSTRACTThe auto‐correlation function of a seismic trace contains information on all the multiple reflection activity present in the trace.The interpretation of this information is facilitated by the arrangement of autocorrelation functions in cross‐sectional form, in the manner of a normal record section. This is the concept of the Sectional Auto‐Correlogram.Specifically, the Sectional Auto‐Correlogram will.Show if the record sectiondoes notinclude significant multiples, thus allowing confident picking of the primary reflections.Show if the record sectiondoesinclude significant multiples, giving their travel times and inclinations (and, under certain circumstances, their reflection coefficients).Indicate by what process the multiples should be treated.Yield an authoritative measure of the success of a multiple‐attenuating treatment.Delineate shallow horizons, even those whose primary reflections are too early to be recorded satisfactorily.Give the true travel time of a primary reflector, and the sign of its reflection coefficient.The Sectional Auto‐Correlogram allows the study of primary reflectors by consideration of the multiples generated by them, and in this sense may be said to turn multiple reflections to advantage. Thus a primary reflection at a certain time is defined if we find that every reflection on the record is followed by a multiple after this certain time. Alternatively, a primary reflection at a certain time is defined if, after that certain time, we can find a repetition of the entire record.The Sectional Auto‐Correlogram also has secondary uses in fault identification, crustal studies and weathe

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1966.tb02245.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

ABSTRACTTwo‐dimensional band‐pass filters can be constructed by a simple extension of the theory of one‐dimensional band‐pass filters. Similarly to the one‐dimensional analogue the shape of the two‐dimensional filter is important in determining its effectiveness. The band‐pass filter formulation can be further refined so that the filter will concentrate its rejection energies in certain areas of the ω,kplane. Such band‐pass, band‐reject filters are found by solving a set of simu

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1966.tb02246.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

ABSTRACTThe common depth point method of shooting in oil exploration provides a series of seismic traces which yield information about the substrata layers at one location. After normal moveout and static corrections have been applied, the traces are combined by horizontal stacking, or linear multichannel filtering, into a single record in which the primary reflections have been enhanced relative to the multiple reflections and random noise.The criterion used in optimum horizontal stacking is to maximize the signal to noise power ratio, where signal refers to the primary reflection sequence and noise includes the multiple reflections. It is shown when this criterion is equivalent to minimizing the mean square difference between the desired signal (primary reflection sequence) and the weighted horizontally stacked traces.If the seismic traces are combined by multichannel linear filtering, the primary reflection sequence will have undergone some phase and frequency distortion on the resulting record. The signal to noise power ratio then becomes less meaningful a criterion for designing the optimum linear multichannel filter, and the mean square criterion is adopted. In general, however, since more a priori information about the seismic traces is required to design the optimum linear multichannel filter than required for the optimum set of weights of the horizontal stacking process, the former will be an improvement over the latter. It becomes evident that optimum horizontal stacking is a restricted form of linear multichannel filtering.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1966.tb02247.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

ABSTRACTIn order to obtain high resolution correlograms, it is of importance amongst other things to get reflection signals with large bandwidth. An advantage of the VIBROSEIS***method is that the frequencies radiated by the vibrators can be matched to the transmission response of the subsurface involved. By choosing the right frequency range, the highest possible amplitude and most favourable form may be given to the reflection signals.In a reflection correlogram, individual signals cannot be considered in isolation. Signals of different origin are interfering with one another. They very often have different amplitudes, so that it may be desirable in many cases to filter out events of certain apparent velocity. With the VIBROSEIS method this may be achieved quite simply. All frequencies of the noise signal are uniformly suppressed. The advantage is that noise signals, e.g. refraction signals, which cannot be sufficiently attenuated by wavelength filtering, may be completely eliminated by this velocity filtering without affecting the bandwith of the desired signal. The total dynamic range of the tape recording can be used for the registration of wanted events. To perform this kind of filtering several vibrators are necessary in the field; each of them is controlled by an individual signal.There is an unavoidable error of static and dynamic corrections which causes the results of reflection measurements to deteriorate when using multiple coverage. High frequency components especially are seriously affected by destructive interference. This difficulty can be avoided by using a VIBROSEIS signal with high frequency component amplitudes supported. For the probability of error of corrections a normal distribution is assumed. A smoothed amplitude characteristic may be achieved after stacking.The amplitude characteristic of seismic devices is commonly reduced to about 100 cps bandwidth. For further improvement of resolution of VIBROSEIS correlograms it is necessary to apply special filtering methods. This is of particular interest when any kind of gain control is used to display weak events more clearly. With increasing amplification the sidelobes of the strong signals may reach the size of the weak events. In order to eliminate this effect, the amplitude characteristic of the VIBROSEIS signal is adjusted for optimum suppression of side‐lobe

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1966.tb02248.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

ABSTRACTIn the inductive method of prospecting, information on conductivity and size of conducting ore‐bodies located in non‐conducting host rocks, can be conveniently obtained by studying amplitude‐frequency relation or amplitude‐phase relation of their response with the help of suitable Master‐curves. Experiments carried out in the laboratory on the scale‐model method show these Master‐curves to be different depending on the type of primary excitation and the shape of conductor. Cases of sphere, plate and disc in uniform field, field of line source and dipole field have been studied with an Amplitude‐Phase Meter specially constructed in the laboratory f

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1966.tb02249.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

AbstractThe development of optically pumped and monitored “atomic” magnetometers has allowed the application of greater resolution in geomagnetic measurements for exploration purposes. This paper presents a survey of instrumentation in use, the variety of exploration techniques that are being used in practice, and an estimate of their state of development.Alkali metals (rubidium and cesium) and helium have been used as active elements to obtain the magnetic‐field dependent Larmor frequency. Each of these instruments is capable of obtaining high resolution data (data with sensitivity numerically smaller than one‐tenth gamma). They have been adapted for airborne, land, and marine usage.Such sensitivity has enabled the rapid development of geomagnetic gradiometers, high sensitivity aeromagnetics, diurnally reduced ground surveys, broad‐band magneto‐telluric surveys, susceptibility measurements, and convenient magnetic search and location techniques. Outlines of each procedure and an example of its application are given.ResumeEn détection des richesses du sol, “les magnétomètres atomiques” qui fonctionnent selon le principe ?un pompage optique ont permis ?obtenir des mesures plus sensibles. Sont décrits les appareillages actuellement utilisés, les méthodes de mesure différentes, ainsi que la situation technique récente.La génération de la fréquence Larmor qui dépend du champ magnétique s'obtient par les métaux alcalins (le rubidium, le césium) et par ľhélium. Chacun des instruments utilisés fournit des résultats de résolution fine, inférieure au dixième du gamma. Des équipements furent réalisés pour ľutilisation aéroportée, sur navire, ainsi que sur terre.De telles sensibilités élevées ont été rendues possibles grâce aux nouveaux gradio‐mètres, aux aéro‐magnétomètres extra‐sensibles, aux mesures des profils terrestres avec correction diurne, aux investigations magnéto‐telluriques large bande, aux mesures de susceptibilityé et aux méthodes pratiques de recherche magnétique.Le sommaire expliqu

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1966.tb02250.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

ABSTRACTRefraction along thin high velocity layers and along basement is investigated in two cases.a) high velocity layer just on the basement.b) high velocity layer higher above.Period and attenuation of refracted waves are given as a function of the layer thickness H. Refracted arrivals along thin high velocity layers are visible at significant distances if the layer thickness is not smaller than A/6, where A is the longitudinal wavelength in high velocity medium. the pseudoperiod is proportional to the layer thickness H. The attenuation at large distance follows an x−ne−k1xlaw, where n is close to I and R1is inversely proportional to H.Refracted arrivals along the basement are observable even in the case of thin high velocity layers situated in the overburden; their intensity is smaller and their pseudoperiod larger than when no layer exists in the overburden. The intensity of the basement arrival decreases and the pseudoperiod increases with increasing laer thickness.The pseudoperiod and the attenuation of refracted arrival along high velocity layers and along the basement are also highly dependent on acoustic contrasts.Both arrivals from a high velocity layer and from the basement can be recorded simultaneously, provided the frequency spectrum of the seismic cbain is sufficiently broad. IN all cases layer arrivals show a character very different from basement arrivals.RESUMELa refraction le long des bancs minces rapides et du socle moins rapide sous‐jacent, est etudiee sur modeles dans deux cas:a) banc rapide reposant directement sur le socle;b) banc rapide situe plus haut dans le recouvrement.La period et l'attenuation des ondes rerractees sont donnees en fonction den l'epaisseur H du banc rapide. Les arrivees refractees le long des bancs rapides ne sont pas visibles sur une distance importante si l'espaisseur de ces bancs est inferieure a A/6 A designant la longueur d'onde longitudinale dans le milieu rapide. La pseudoperiode est proportionnelle a l'epaisseur H du banc. L'attenuation a grande distance suit une loi eb x−ne−k1xavec n voisin de l et k1inversement proportionnel a H.Les arrivees refractees le long du socle sont observables en presence de bancs minces rapides dans le recouvrement, mais avec des internsites plus faibles que dans le cas d'unrecouvrement homogene. La pseudoperiode des impulsions refractees du socle augmente avec l'epaisseur H du banc rapide. L'attenuation en fonction de la distance est superieure a l'attenuation observee pour un recouvrement homogene, et elle croit avec H.La pseudo‐periode et l'attenuation des arrivees refractees le long des bancs rapides et des marqueurs sous‐jacents sont largement fonction des impedances acoustiques des milieux en presence.Les arrivees d'un banc mince rapide et socle peuvent etre observees simultanement a condition que la chaine d'enregistrement ait un spectre en frequence suffisamment large. On constate dans tous les cas que le caractere des arrivees des bancs est tres different du caractere des arri

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1966.tb02251.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

ABSTRACTDownward continuation of the field in the neighborhood of a singularity of a magnetic anomaly is used to render the anomaly more two‐dimensional, to make the bottom of the causal body more remote, and to obtain an auxiliary function, φ (O, z), by means of which the anomaly may be interpreted in terms of an equivalent vertical contact or step model. The concept of “apparent depth” is introduced and used in studying depth extent and susceptibility. The methods are illustrated with theoretical and practical ex

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1966.tb02252.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

ABSTRACTThe occurrence of shingling in. long range refraction records often makes the task of the seismic interpreter heavier, especially when several refractors are encountered and the velocity contrasts are small.The explanation of the phenomenon given by the existing literature is examined and the theoretical results are compared with the observed data on field records.In field seismograms shingling must be separated from the effect of geological structures or lateral discontinuities.If an appropriate analysis of shingling is possible, this phenomenon can be related to the type of refracting layer, being a useful tool to a qualitative approach.On the other hand the implications of shingling are examined on the side of the geometrical interpretation

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1966.tb02253.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1966.tb02254.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY