A comparison of numerical, analogue model, and field-station vertical magnetic-fields for the Vancouver Island region

Ramaswamy, V.; Jones, F. W.; Dosso, H. W.; Nienaber, W.

doi:10.1016/0031-9201(80)90101-6

Cited by 16 publications

(5 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…~*r T6; Island. In a compelling and convincing comparison of a scale modelling experiment (Figure 2a), 3D numerical modelling by finite differences (Jones and Pascoe 1973), and field data (Figure 2b), Ramaswamy et al (1980) illustrated that the field observations can all be well described by 'local' induction in the region around Vancouver Island and part of the British Columbian and northwestern U.S.A. mainland, with associated current perturbation effects around the island (see Figure 2b). Hence, I do not consider that the 'current channelling' effects here are a 'problem' however, they certainly would have been if the field observations were not compatible with the numerical and analogue 3D models (more consideration is given to these observations in the Conclusions).…”

Section: Introductory Remarksmentioning

confidence: 93%

The problem of current channelling: A critical review

Jones

1983

Geophysical Surveys

147

View full text Add to dashboard Cite

Abstract. The notion that currents induced 'elsewhere', by external source fields, could wend their way in a frequency-independent ohmic-like manner through a region of interest has been the cause of many recent disputes within the geomagnetic induction community. In particular, two-dimensional (2D) models of the Rhinegraben, and of the region known as the 'Eskdalemuir anomaly' in southern Scotland, have been dismissed as erroneous by those who believe that the observations are more correctly interpreted as due to the effects of 'channelled' currents rather than 'induced' currents. In this review, attention is paid primarily to consider under what circumstances any perturbation of current flow, which may manifest itself as a 'DC-like' channelled current, could cause a 'problem' for those wishing to interpret their observations. Various concepts are introduced, particularly the ratio of 3D/2D current channelling numbers for the induction problem, which is shown to be the ratio of the length of the 3D body to the skin depth in the host medium. It is stressed that the worker must analyse his data by adequate statistical techniques, and that the simplest physical models possible, that describes the observations, must be sought. Finally, suggestions are made for further work to be undertaken.

show abstract

Section: Introductory Remarksmentioning

confidence: 93%

The problem of current channelling: A critical review

Jones

1983

Geophysical Surveys

147

View full text Add to dashboard Cite

show abstract

“…The simplest idea of how to interpret 3D anomalies is the selection of models available. In several recent investigations this approach provided quite satisfactory model fitting of EM array observations Ramaswamy et al, 1980;Weaver, 1982;etc.). An automatic search for the best fitting 3D model in an exisiting bank of modelling results seems to be realistic in simple geoelectric situations, as in the 2D case (Pelton et al, 1978).…”

Section: Outlines Of Solution Of 3d Inverse Problemsmentioning

confidence: 91%

“…Several types of field excitation were considered (Hibbs et al, 1978;Ramaswamy and Dosso, 1978;Miles and Dosso, 1979). The problem of modelling accuracy was specially studied using some simple analytical estimates and compared with numerical 3D modelling (Hibbs et at., 1978;Ramaswamy et al, 1980). New analogue laboratories to analyse a more general class of conductivity structures (subsurface and deep inhomogeneities in a multi-layered normal model) appeared in the USSR (Moroz et al, 1975(Moroz et al, , 1978 and in Hungary (~.d~m et al, 1981).…”

Section: Analogue Scale Modellingmentioning

confidence: 96%

“…These studies contain a set of theoretical models describing 3D coast and island EM effects (Nienaber et al, 1977;Chan et al, 1981;etc. ) as well as more complicated regional models of real coastal conductivity structures (Dosso et al, 1980a, b;Ramaswamy et al, 1980;. Several types of field excitation were considered (Hibbs et al, 1978;Ramaswamy and Dosso, 1978;Miles and Dosso, 1979).…”

Section: Analogue Scale Modellingmentioning

confidence: 99%

“…The comparison of 3D numerical and analogue modelling results was performed by several authors (Hibbs et al, 1978;Ramaswamy et al, 1980;Lee et at., 1981 ;Das and Verma, 1982) and it can be seen that modern analogue models are often more detailed and at least as accurate as numerical ones (Ramaswamy et at., 1980).…”

Section: Analogue Scale Modellingmentioning

confidence: 99%

See 2 more Smart Citations

Modern trends in the solution of forward and inverse 3D electromagnetic induction problems

Варенцов

1983

Geophysical Surveys

View full text Add to dashboard Cite

Abstract. The main results obtained during the last 5-8 yr in the solution of forward and inverse problems of 3D induction studies are summarized. The up-to-date status of 3D modelling is presented and prospective improvements in the formulation and numerical solution of forward problems are discussed. Approximate techniques and practical aspects of 3D modelling are specially considered.The general scheme of 3D interpretation of electromagnetic geophysical observations is outlined and realistic formalized approaches to solving 3D inverse problems, namely direct inversion and formalized model fitting, are studied. O. IntroductionThe significant progress in the development of electromagnetic (EM) array observations achieved during the last ten years made it necessary to elaborate the system of EM data interpretation in 3D environments. Theoretical studies of 3D problems have been carried out during the last twenty years or more, but not until a few years ago did these works become of practical importance and serious applied researches were begun. Now many publications concerned with 3D induction studies are well known. Still, we have no generalized reviews on this subject (except brief ones like Ward, 1980), but in many special papers meaningful discussions of the problems and outlines of 3D techniques have been presented (Weidelt, 1975a;Vasseur and Weidelt, 1977;Hohmann, 1978;Banks, 1979;Weaver, 1979;Dawson and Weaver, 1979, Fainberg, 1980;Lee et al., 1981;Stodt et al., 1981;Berdichevsky et al., 1982; etc).It looks quite unrealistic to consider in detail the significant achievements in all of the numerous branches of 3D induction studies in a single review. Therefore the subject of this paper is restricted to the study of interpretation techniques of time-harmonic EM field anomalies caused by local and regional 3D conductivity structures. Moreover, attention is paid mainly to the theoretical and computational aspects of the rational formulation and effective solution of 3D forward and inverse problems. These problems form the basis of the interpretation theory and, as it can be seen from the experience of 2D induction studies, their intensive development produces the evident progress in elaboration of the whole interpretation system. It is not surprising that these problems are prevalent in the majority of publications of recent years.It should be noted that general ideas of inhomogeneous media interpretation theory, well illustrated in 2D applications, can be expressed in the main in 3D formulations. This has been shown clearly in the last monographs of Zhdanov (1981, 1983). However, we have usually enough difficulties to overcome in the theoretical analysis and at the stage of numerical considerations. Really, in most 3D

show abstract