PROCEDURE AND DEVICE FOR THE DETECTION OF INVERSIONS OF THE EARTH'S MAGNETIC FIELD BY MEANS OF MEASUREMENT TAKEN IN A DRILL SHAFT

A method and device for detecting inversions of the earth's magnetic field by taking measurements in a drill shaft. The device includes a first probe used to measure the magnetic induction B1 during its movement in the shaft, a sensor to measure magnetic induction B2 on the surface of the ground at a stationary point at the same time as B1 is measured, a second probe to measure magnetic susceptibility X of the rocks as it moves through the shaft, and a data-recording and data-processing unit. The data-recording and data-processing unit further includes a device for calculating a value of B1-B2, filtering the calculated value to isolate the induction fraction BL, which is only composed of a component BI resulting from an induced magnetization, and the component BR resulting from the residual magnetization. The induction BI based on the induction B1 in the shaft and on the magnetic susceptibility X can be calculated.