Study of Earth Tides, Earthquakes and Terrestrial Spectroscopy by Analysis of the Level Fluctuations in a Borehole at Heibaart (Belgium)

The article describes the installation of a tidal recorder on the borehole at Heibaart (Belgium) for the study of earth tides caused by the cubic expansion of the Earth. The results of the harmonic analysis of the curve of the level fluctuations in relation to time are given. The behaviour as a seismograph is described, with the characteristics observed during the earthquake which occurred on 1968 May 16 near Hokkaido in North Japan. The analysis of the recorded diagram shows periods of the free oscillations of the Earth.