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DETERMINATION OF ELECTRICAL PROPERTIES OF THE GROUND AT SHALLOW DEPTH WITH AN ELECTROSTATIC QUADRUPOLE: FIELD TRIALS ON ARCHAEOLOGICAL SITES 1
Author(s) -
TABBAGH ALAIN,
HESSE ALBERT,
GRARD RÉJEAN
Publication year - 1993
Publication title -
geophysical prospecting
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.735
H-Index - 79
eISSN - 1365-2478
pISSN - 0016-8025
DOI - 10.1111/j.1365-2478.1993.tb00872.x
Subject(s) - electrical resistivity and conductivity , permittivity , quadrupole , dielectric , frequency domain , prospecting , materials science , mineralogy , relative permittivity , low frequency , geology , geophysics , physics , optoelectronics , mathematics , atomic physics , mathematical analysis , quantum mechanics , astronomy , metallurgy
A bstract Knowledge of both the electrical resistivity ρ and the dielectric permittivity ɛ of the ground is important for the determination of characteristics such as granularity, porosity, moisture and salt content. Whereas the measurement of ρ is very common and can be achieved using either the d.c. resistivity method or a wide variety of EM devices, ɛ remains practically unknown in the low‐frequency domain between the IP domain and the high‐frequency domain. Following the principle of the quadrupole technique used in d.c. prospecting and of the quadrupolar probe for measuring the complex permittivity of the ionosphere, we propose a new approach which does not require any galvanic contact between the poles and the ground. The transfer impedance can be evaluated using the quasi‐static approximation for low frequency or the full EM theory for higher frequencies. The conditions under which both calculations apply are discussed. At low frequencies and for low resistivity ground, the electrostatic quadrupole measures ρ exactly as with the d.c. technique; for higher resistivities or frequencies the simultaneous measurement of both properties becomes possible. Examples in archaeological prospecting are presented and checked against independent d.c. resistivity measurements or excavation analyses.