f Shallow depth and civil engineering applications of a non conductive electrostatic quadrupole for ground resistivity measurements

The concept of the electrostatic quadrupole we use is derived from classic d.c. resistivity techniques as well as from the quadrupolar probes adapted for measuring the complex permittivity of the ionosphere (Storey et al 1969). When approaching the ground surface with an electrostatic charge, the electrical potential at any point in the vicinity of this charge is modified and depends on the electrical properties of the ground. In fact, it is not possible to maintain a constant static charge in the vicinity of the ground surface and one has to use two poles exchanging their charges alternatively at a given frequency, f. The voltage generated by these two poles is measured between two other poles. The apparatus can then be Galled a "quadrupolar probe". However, for ground application on the Earth's surface we prefer to use the word "electrostatic quadrupole" which both suggests its proximity to the d.c. resistivity method and indicates that the injection of electrical current into the ground is made by electrostatic influence .