Abstract
Earth's free oscillations excited independently of earthquakes were detected by the vertical strain seismograph being in operation at the Amagase Observatory, Kyoto University, Japan. Though weak, diurnal variation in Earth's background free oscillations was evident. The maximum and the minimum of diurnal variations were found in intervals from 14 to 16 o'clock (JST) and from 6 to 8 o'clock (JST), respectively. It was also found that the feature of the diurnal variation above mentioned was evident in the summer of the northern hemisphere and disturbed in the winter.
