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Earth's continuous oscillations observed on seismically quiet days
Author(s) -
Tanimoto Toshiro,
Um Junho,
Nishida Kiwamu,
Kobayashi Naoki
Publication year - 1998
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/98gl01223
Subject(s) - quiet , gravimeter , earth (classical element) , geodesy , amplitude , acceleration , geology , geophysics , physics , excitation , tectonics , excited state , seismology , atomic physics , classical mechanics , astronomy , casing , quantum mechanics
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.