DETECTION SENSOR FOR THREE-DIMENSIONAL COMPONENT OF UNDERGROUND ELECTROMAGNETIC WAVE

PROBLEM TO BE SOLVED: To detect a horizontal electric field component of feeble underground electromagnetic waves with long wavelength with sufficient sensitivity in a narrow borehole for observation provided underground.SOLUTION: As a detection sensor for horizontal electric field component, many short dipole antenna elements consisting of a pair of linear conductors whose full length is smaller than an inner diameter of a borehole for observation are arranged in parallel with the depth direction by separating them from one another for predetermined separation distance or more, elements on one side of the respective short dipole antenna elements are connected to an input of one side of a differential amplifier via a capacitor C, elements on the other side are connected to on input on the other side of the differential amplifier via the capacitor C, respectively, potential difference between the elements on both sides of the respective short dipole antennas is added by detecting the potential difference by the total value of electric charges to be inducted by capacitance C(