Numerical VLF Modeling*

KAROUS, M. and HJELT, SE. 1983, Linear Filtering of VLF Dip-Angle Measurements, Geophysical Prospecting 3 1, 782-794.The suggested interpretation technique is based on discrete linear filtering of VLF data. The output of the described filtering results is expressed in terms of an equivalent current density at a specified depth that would cause the measured magnetic field. The most practical six-point filter gives an accuracy of 8%. The filter is an extension of the commonly used Fraser filter to process VLF dip-angle data.Filtering the same data set for various depths gives an idea about the change of current density with depth. Areas with high current-density correspond to good conductors. The conductor dip can also be determined.The use of the technique is illustrated on theoretical and field examples. In all cases a good correlation with original models and other types of geophysical measurements was obtained. As shown in the last example, the filtering technique is also applicable in interpretation of other electromagnetic methods.

show abstract

“…Trial runs with the proposed discrete filters were made on VLF anomalies calculated by Kaikkonen (1979)…”

Section: Application O F T H E Filter To Theoretical Curvesmentioning

confidence: 99%

Linear Filtering of VLF Dip‐angle Measurements*

Karous

Hjelt

1983

Geophysical Prospecting

227

139

View full text Add to dashboard Cite

show abstract

“…The EM field is effectively planar and horizontal at large distances from the transmitter, so that a conductor that strikes in the direction of the transmitter is cut by the magnetic vector. As a result, the primary magnetic fields cause electrical currents to flow through subsurface conductors, and both the in-phase (real) and out-of-phase (quadrature) components of the induced magnetic field are easily measured (Vozoff, 1971;Kaikkonen, 1979, Saydam, 1981Wright, 1988). The method is generally used to locate sources such as conductive fractures and faults, groundwater resources, and buried conductive shallow geological structures.…”

Section: Methodsmentioning

confidence: 99%

Geophysical investigations of the Seferihisar geothermal area, Western Anatolia, Turkey

Drahor

Berge

2006

Geothermics

View full text Add to dashboard Cite

“…We are interested in the two most important VLF parameters in the E-polarization on the surface of the Earth (z = 0), namely the apparent resistivity, pa, and tan 8, where 8 is the inclination of the major axis of the polarization ellipse of the magnetic field vector (Smith and Ward 1974, Kaikkonen 1979, Bezvoda and Segeth 1982a, 1982b. We are interested in the two most important VLF parameters in the E-polarization on the surface of the Earth (z = 0), namely the apparent resistivity, pa, and tan 8, where 8 is the inclination of the major axis of the polarization ellipse of the magnetic field vector (Smith and Ward 1974, Kaikkonen 1979, Bezvoda and Segeth 1982a, 1982b.…”

Section: A Test Example For the V L F Methodsmentioning

confidence: 99%

An Application of Fast Algorithms to Numerical Electromagnetic Modeling*

Bezvoda

Segeth

1987

Geophysical Prospecting

View full text Add to dashboard Cite

Numerical electromagnetic modeling by the finite‐difference or finite‐element methods leads to a large sparse system of linear algebraic equations. Fast direct methods, requiring an order of at most q log q arithmetic operations to solve a system of q equations, cannot easily be applied to such a system. This paper describes the iterative application of a fast method, namely cyclic reduction, to the numerical solution of the Helmholtz equation with a piecewise constant imaginary coefficient of the absolute term in a plane domain. By means of numerical tests the advantages and limitations of the method compared with classical direct methods are discussed. The iterative application of the cyclic reduction method is very efficient if one can exploit a known solution of a similar (e.g., simpler) problem as the initial approximation. This makes cyclic reduction a powerful tool in solving the inverse problem by trial‐and‐error.

show abstract

Numerical VLF Modeling*

Abstract: KAIKKONEN, P., 1979. Numerical VLF Modeling, Geophysical Prospecting 27, 815-834.

Cited by 47 publications

References 9 publications

Linear Filtering of VLF Dip‐angle Measurements*

Linear Filtering of VLF Dip‐angle Measurements*

Geophysical investigations of the Seferihisar geothermal area, Western Anatolia, Turkey

An Application of Fast Algorithms to Numerical Electromagnetic Modeling*

Contact Info

Product

Resources

About