Earth's continuous oscillations observed on seismically quiet days

Abstract

Analysis of IDA gravimeter data between 1983 and 1994 and GEOSCOPE data between 1988 and 1994 show that fundamental modes of the Earth, for frequencies between 2 and 7 mHz , are excited even on seismically quiet days. Amplitudes of acceleration are slightly less than one ngal (10 −9 gal ). Examination of a sequence of shorter time interval records suggests that the Earth is oscillating continuously. Currently, both atmospheric excitation and tectonic motions are possible cause(s) of these oscillations.