Subtraction of powerline harmonics from geophysical records

Geophysics ◽  
1993 ◽  
Vol 58 (6) ◽  
pp. 898-903 ◽  
Author(s):  
Karl E. Butler ◽  
R. Don Russell
Keyword(s):  
North America ◽  
Magnetic Fields ◽  
Fundamental Frequency ◽  
Time Domain ◽  
Seismic Data ◽  
Power Transmission ◽  
Power Lines ◽  
Electric And Magnetic Fields ◽  
Harmonic Noise

Harmonic noise generated by power lines and electric railways has plagued geophysicists for decades. The noise occurs as electric and magnetic fields at the fundamental frequency of power transmission (typically 60 Hz in North America) and its harmonics. It may be recorded directly during time‐domain measurements of electric and magnetic felds, or indirectly, by geophone cables during the acquisition of seismic data.

Radiation in Materials

2019 ◽  
pp. 303-365
Author(s):  
Richard Freeman ◽  
James King ◽  
Gregory Lafyatis
Keyword(s):  
Magnetic Fields ◽  
Time Domain ◽  
Measurement Techniques ◽  
Group Versus ◽  
Index Of Refraction ◽  
The Real ◽  
Versus Phase ◽  
Fundamental Relationship ◽  
Electric And Magnetic Fields ◽  
The Time Domain

The interaction of electromagnetic radiation and matter is examined, specifically electric and magnetic fields in materials with real and imaginary responses: under certain conditions the fields move through the material as a wave and under others they diffuse. The movement of a pulse of radiation in dispersive materials is described in which there are two wave velocities: group versus phase. The reflection of light from a sharp interface is analyzed and the Fresnel reflection/transmission equations derived. The response of materials to applied electric and magnetic fields in the time domain are correlated to their frequency response of the material’s polarization. The generalized Kramers–Kronig equations are derived and their applicability as a fundamental relationship between the real and imaginary parts of any material’s polarizability is discussed in detail. Finally, practical measurement techniques for extracting the real and imaginary components of a material’s index of refraction are introduced.

Cardiac Pacemakers in Electric and Magnetic Fields of 400-kV Power Lines

2012 ◽  
Vol 35 (4) ◽  
pp. 422-430 ◽  
Author(s):  
LEENA KORPINEN ◽  
HARRI KUISTI ◽  
JARMO ELOVAARA ◽  
VESA VIRTANEN
Keyword(s):  
Magnetic Fields ◽  
Power Lines ◽  
Cardiac Pacemakers ◽  
Electric And Magnetic Fields

A time‐domain EM system measuring the step response of the ground

Geophysics ◽  
1984 ◽  
Vol 49 (7) ◽  
pp. 1010-1026 ◽  
Author(s):  
G. F. West ◽  
J. C. Macnae ◽  
Y. Lamontagne
Keyword(s):  
Magnetic Fields ◽  
Impulse Response ◽  
Electric Fields ◽  
Time Domain ◽  
Wide Band ◽  
Step Response ◽  
System Function ◽  
Response Measurement ◽  
Resistivity Method ◽  
Electric And Magnetic Fields

A wide‐band time‐domain EM system, known as UTEM, which uses a large fixed transmitter and a moving receiver has been developed and used extensively in a variety of geologic environments. The essential characteristics that distinguish it from other systems are that its system function closely approximates a stepfunction response measurement and that it can measure both electric and magnetic fields. Measurement of step rather than impulse response simplifies interpretation of data amplitudes, and improves the detection of good conductors in the presence of poorer ones. Measurement of electric fields provides information about lateral conductivity contrasts somewhat similar to that obtained by the gradient array resistivity method.

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