scholarly journals VLF surface-impedance measurements for ice-depth mapping — an assessment of some commonly encountered interference effects

1996 ◽  
Vol 42 (140) ◽  
pp. 33-36 ◽  
Author(s):  
David V. Thiel ◽  
Daniel James ◽  
Peter Johnson
Keyword(s):  
Surface Impedance ◽  
Apparent Resistivity ◽  
Low Frequency ◽  
Two Dimensional ◽  
Interference Effects ◽  
Impedance Measurements ◽  
Very Low Frequency ◽  
Dimensional Boundary ◽  
Lateral Variations ◽  
Made In

AbstractThe effects on very low-frequency surface-impedence measurements of lateral variations commonly found in ice environments have been measured and modelled numerically using die quasi-static two-dimensional boundary-element method. Results indicate that surface-impedance measurements made in the vicinity of crevasses oriented perpendicular to the plane Of incidence, and those made in the vicinity of moraines and melt streams, can all show significant changes to the measured apparent resistivity. It is, therefore, misleading to use such measurements in the interpretation of ice depth.

scholarly journals VLF surface-impedance measurements for ice-depth mapping — an assessment of some commonly encountered interference effects

1996 ◽  
Vol 42 (140) ◽  
pp. 33-36
Author(s):  
David V. Thiel ◽  
Daniel James ◽  
Peter Johnson
Keyword(s):  
Surface Impedance ◽  
Apparent Resistivity ◽  
Low Frequency ◽  
Two Dimensional ◽  
Interference Effects ◽  
Impedance Measurements ◽  
Very Low Frequency ◽  
Dimensional Boundary ◽  
Lateral Variations ◽  
Made In

AbstractThe effects on very low-frequency surface-impedence measurements of lateral variations commonly found in ice environments have been measured and modelled numerically using die quasi-static two-dimensional boundary-element method. Results indicate that surface-impedance measurements made in the vicinity of crevasses oriented perpendicular to the plane Of incidence, and those made in the vicinity of moraines and melt streams, can all show significant changes to the measured apparent resistivity. It is, therefore, misleading to use such measurements in the interpretation of ice depth.

SOURCE DISTANCE DEPENDENCE OF THE SURFACE‐IMPEDANCE CONDUCTIVITY MEASUREMENT TECHNIQUE

Geophysics ◽  
1969 ◽  
Vol 34 (5) ◽  
pp. 785-788 ◽  
Author(s):  
Peter R. Bannister
Keyword(s):  
Measurement Technique ◽  
Surface Impedance ◽  
Low Frequency ◽  
Conductivity Measurement ◽  
Very Low Frequency ◽  
Extremely Low Frequency ◽  
Source Distance ◽  
Distance Dependence ◽  
Magnetotelluric Method

The surface impedance conductivity measurement technique, commonly called the magnetotelluric method (Wait, 1962a), has been employed for many years at frequencies below 1 Hz. Recently, frequencies in the extremely low frequency (ELF) and very low frequency (VLF) bands have been employed (Watt et al, 1963).

Very low frequency SQUID NMR measurements of two-dimensional solid films

2003 ◽  
Vol 329-333 ◽  
pp. 148-149
Author(s):  
A. Casey ◽  
C. Lusher ◽  
B. Cowan ◽  
J. Saunders
Keyword(s):  
Low Frequency ◽  
Two Dimensional ◽  
Very Low Frequency ◽  
Solid Films ◽  
Squid Nmr

Extracting geoelectrical maps from vintage very-low-frequency airborne data, tipper inversion, and interpretation: A case study from northern Sweden

Geophysics ◽  
2016 ◽  
Vol 81 (5) ◽  
pp. B135-B147 ◽  
Author(s):  
Sayyed Mohammad Abtahi ◽  
Laust Börsting Pedersen ◽  
Jochen Kamm ◽  
Thomas Kalscheuer
Keyword(s):  
Magnetic Field ◽  
Apparent Resistivity ◽  
Vertical Component ◽  
Low Frequency ◽  
High Resistivity ◽  
Clear Correlation ◽  
Northern Sweden ◽  
Very Low Frequency ◽  
Basaltic Composition ◽  
The Magnetic Field

In 1985, the mining company Luossavaara-Kiirunavaara Aktiebolag collected airborne very-low-frequency (VLF) data in northern Sweden. The operators stored only the vertical component and the total magnetic field, which at that time were believed to be sufficient for qualitative interpretation. Therefore, the data could not be directly used for quantitative tensor VLF processing and inversion. To avoid the costs of resurveying, we have developed a novel technique to estimate the tippers from the measured VLF data by computing anomalous and normal parts of the horizontal components of the magnetic field from two transmitters separately. Retrieval of the normal horizontal components was possible because one component of the horizontal magnetic field was used as the phase reference during the measurements. Additionally, we have determined how the approximate apparent resistivity suitable for data visualization can be computed from the components of the magnetic field assuming an average normal resistivity of the subsurface. Maps of apparent resistivity combined with topography show a clear correlation between high topography and high resistivity, whereas conductive zones are found in valleys in between. More importantly, the 3D model inverted from the calculated tippers shows excellent agreement with a map of the surface geology. Based on this comparison, some less resistive zones can be related to fluids in fractures and others can be related to mineralized contact zones. We suggest to focus further exploration on conductive zones surrounding areas with basaltic composition.

Sign in / Sign up

Export Citation Format

Share Document