ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1976.tb00942.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1976.tb00943.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1976.tb00944.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1976.tb00945.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1976.tb00946.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe manner in which boundary conditions are approximated and introduced into finite difference schemes may have an important influence on the stability and accuracy of the results. The standard von Neumann condition for stability applies only for points which are not in the vicinity of the boundaries. This stability condition does not take into consideration the effects caused by introducing the boundary conditions to the scheme.Working on elastic media with free stress boundary conditions we found that the boundary approximation gives rise to serious stability problems especially for regions with high Poisson's ratio. In order to detect these effects apriori and to analyse them, we have used a more elaborate procedure for checking the stability of the scheme which takes into consideration the boundary conditions. It is based on studying a locally spaced time propagating matrix which governs the time‐space behavior of a small region of the grid which includes free surface points.By using this procedure a better insight into the nature of instability caused by the approximations to the boundary conditions was gained which led us to a new stable approximation for the free surface boundary condition

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1976.tb00947.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractIn modern exploration for hydrocarbons there is a great emphasis on the location of stratigraphic traps and estimation of lithologic information like sand‐shale ratios from seismic data. In order to investigate the possibilities of success in this endeavour we have studied the synthetic seismograms for wave form and spectral characteristic for four basic sedimentation models: (I) interbedded sand‐shale model representing the sediments of generally fluviatile origin, (2) interbedded coal‐shale model representing deltaic deposits, (3) sedimentary models representing transgression and regression of shore lines, and (4) a basal sand model. The results have shown that for the first two models a change in the sand‐shale or coal‐shale ratio results in a characteristically different seismogram. The nature of the seismogram, however, is also strongly dependent on how the sand‐shale or coal shale layers are arranged to ultimately give the same number of total layers, thus implying the same coal‐shale or sand‐shale ratios. The transgression, regression, and basal sand models also produce characteristically different seismic signatures. The spectra of these seismograms show attendant characteristic changes. However, it seems that in the case of real data which are disturbed by noise and the effects of overlying layers these characteristic features may not always be

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1976.tb00948.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractVarious Dix‐type formulae are derived, which are useful to approximate travel time functions that can be observed while modeling the common depth point (CDP) technique for 3‐D isovelocity layers of varying dip and strike. All formulae can be used to compute interval velocities and recover the depth model from surface measurements. They are established by making use of the concept of wavefront curvature. Many similarities with known formulae valid for the 2‐D plane isovelocity layer case

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1976.tb00949.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe main problem in seismic prospecting is to infer from the observed reflection response the distribution of density and seismic velocity with depth. This process is generally called the inversion of the reflection data.For plane waves propagating through plane parallel stratification, it can be shown that at any depth the ratio between the amplitude of the transmitted and reflected wave satisfies the Riccati equation. Based on this equation we have formulated an iterative inversion method, which is found to be suitable for numerical computations. We have applied this method on synthetic reflection data, and found that it provides a very fast and accurate inversion.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1976.tb00950.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractMis‐ties are all‐too‐common results of seismic surveys made at the same place but at different times with different equipment or by different organizations. Even after removal of positioning or polarity errors, reflection times often appear to differ by several tens of milliseconds. Zero time appears to fluctuate.How can zero time differ on surveys with only minor differences in acquisition or processing? What can be done to identify the true zero time for each survey?The first step toward establishing zero time is to record the source pulse. It is well‐known that the different sources currently used in reflection seismic prospecting (propane‐oxygen explosions, compressed‐air discharges, explosives, steam bubbles, mechanical implosions, vibrations, etc.) yield different pressure wavefronts as the input to the seismic reflection system. By recording this wavefront we capture the basic pulse shape and we establish the initial time delay.The second step is to process the recorded source pulse as if it were reflection data to establish the additional time and shape changes introduced by data processing. Then, display the recorded and processed source pulse as an auxiliary variable at the ends of the seismic section. From this display the interpreter can systematically establish the time shifts appropriate to each picked event. He can determine also whether the pick should be a peak or a trough. He can see why surveys which appear to tie for shallow reflections appear to mis‐tie for deep reflections.The display of the processed source pulse constitutes a major interpretation aid which, in a readily useable form, increases the information content of the basic se

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1976.tb00951.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY