摘要:

ABSTRACTIn one‐way wave field extrapolation downgoing and upgoing waves are treated independently, which is allowed if propagation at small angles against the vertical in (weakly) inhomogeneous media is considered. In practical implementation the slow convergence of the square‐root operator causes numerical deficiencies. On the other hand, in two‐way wave field extrapolation no assumptions need to be made on the separability of downgoing and upgoing waves. Furthermore, in practical implementation the use of the square‐root operator is avoided. To put the two‐way techniques into perspective, it is shown that two‐way wave field extrapolation could be described in terms of one‐way processes, namely: (1) decomposition of the total wave field into downgoing and upgoing waves; (2) one‐way wave field extrapolation; (3) composition of the total wave field from its downgoing and upgoing constituents. This alternative description of two‐way wave field extrapolation is valid for media which are homogeneous along thez‐coordinate as well as for small dip angles in arbitrarily inhomogeneous media. In addition, it is shown that this description is also valid for large dip angles in 1‐D (vertically) inhomogeneous media, including critical‐angle events, when the WKBJ one‐way wave functions discussed in part I of this paper are considered.For large dip angles in arbitrarily inhomogeneous media the two‐way wave equation is solved by means of Taylor series expansion. For practical implementation a truncated operator is designed, assuming gentle horizontal variations of the medium properties. This operator is stable and converges already in the first order approximation, als

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1986.tb00461.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractWave field extrapolation including critical angle events in modeling, migration and inversion can be handled with algorithms based on both the one‐way wave equations and the two‐way wave equation. It is shown that for 1‐D inhomogeneous media, critical angle events as well as multiple reflections may elegantly be included in pre‐stack modeling, pre‐stack migration and velocity inversion. For 2‐D and 3‐D inhomogeneous media a powerful pre‐stack migration scheme can be developed which includes critical angle events as well as multiple reflections. Finally, suggestions for practical applica

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1986.tb00462.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACTA new inversion method for seismic reflection data is based on impedance concepts and uses transformations to reduce the essentially non‐linear problem to a linear eigenvalue formulation without approximation. A set of reflection data has been inverted using this method. The characteristic impedances of the layers so determined are compared with log data from a reference borehol

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1986.tb00463.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe application of pulse EM and MAXMIN II systems in search of a kimberlite diatremes under conducting cover has been demonstrated through a field example. The effectiveness of the PEM system in the search for conductive zones of economic importance and in discrimination against geologic noise such as overburden has been investigated. The transient observation has been transformed to equivalent half‐space resistivities at various times. The feasibility of mapping thin conducting overburden using the PEM system has been studied by inverting the transient measurement to the thin infinite horizontal sheet conductance. The PEM measurement is shown to be an economic and effective tool for shallow geoelectric mappin

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1986.tb00464.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

ABSTRACTThe in‐loop pulse electromagnetic response of a stratified earth has been expressed in terms of an apparent resistivity‐ time plot using the PEM response over a homogeneous half‐space which is typically unipolar with monotonic decay. This half‐space response characteristic provides a unique relationship between Crone PEM channel amplitude and the apparent half‐space resistivity. The possibility to resolve a thin intermediate conductive and resistive layer with the in‐loop PEM system has been investigated. The system is well in shallow geoelect

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1986.tb00465.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1986.tb00466.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1986.tb00467.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY