Cross‐borehole electromagnetic probing to locate high‐contrast anomalies

Autor:	D.T. Davis, R. J. Lytle, E.F. Laine, Darrel L. Lager
Rok vydání:	1979
Předmět:	Electromagnetic field Diffraction Field (physics) Acoustics Transmitter Borehole Mineralogy Field strength Condensed Matter::Mesoscopic Systems and Quantum Hall Effect Signal Maxima and minima Geophysics Geochemistry and Petrology Geology
Zdroj:	GEOPHYSICS. 44:1667-1676
ISSN:	1942-2156 0016-8033
Popis:	Electromagnetic (EM) probing between boreholes is useful for locating high‐contrast geophysical anomalies such as a tunnel. Theoretical and experimental studies of EM field interaction with a tunnel show that minima in the received signal can be used for locating the tunnel. The theoretical studies show that as a transmitter and receiver are lowered in separate boreholes, the minima can be interpreted easily to yield both the lateral and vertical positions of the tunnel. The main mechanism of EM field interaction with the tunnel appears to be diffraction, and the spatial variation of the field strength is affected by the tunnel shape. Frequencies from 10 to 70 MHz were studied to assess the usable frequencies. The field in the receiver borehole was an effective diagnostic when a half‐wavelength in the surrounding medium was less than or equal to the diameter of the tunnel. EM probing at two test sites gave the locations of tunnels within 1 ft of the surveyed locations.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::4761adaec6e581c2eb4285c378ff3929 https://doi.org/10.1190/1.1440929 Zobrazit plný text záznamu