TY - JOUR
T1 - Incessant excitation of the Earth's free oscillations
T2 - Global comparison of superconducting gravimeter records
AU - Nawa, Kazunari
AU - Suda, Naoki
AU - Fukao, Yoshio
AU - Sato, Tadahiro
AU - Tamura, Yoshiaki
AU - Shibuya, Kazuo
AU - McQueen, Herbert
AU - Virtanen, Heikki
AU - Kääriäinen, Jussi
PY - 2000/8
Y1 - 2000/8
N2 - Records of superconducting gravimeters (SGs) at Canberra (Australia), Esashi (Japan), Metsahovi (Finland) and Syowa Stations (Antarctica) were analyzed to search for further evidence of background free oscillations of the Earth. Spectrograms for 1-year period and averaged power spectra for seismically quiet periods were obtained for each of the stations. Anomalous features of the oscillations observed at Syowa Station, such as an apparent seasonal variation and a high intensity at frequencies between 3 and 4 mHz, were absent at the other SG stations. Among the SG stations used in this study, the background free oscillations were detected most consistently and distinctly at Canberra, where the noise level was comparable to that at the IDA quietest station, while that at Syowa Station was close to the critical limit for detecting the oscillations. The background free oscillations provide a good reference to evaluate the noise level in the milliHertz band. (C) 2000 Elsevier Science B.V. All rights reserved.
AB - Records of superconducting gravimeters (SGs) at Canberra (Australia), Esashi (Japan), Metsahovi (Finland) and Syowa Stations (Antarctica) were analyzed to search for further evidence of background free oscillations of the Earth. Spectrograms for 1-year period and averaged power spectra for seismically quiet periods were obtained for each of the stations. Anomalous features of the oscillations observed at Syowa Station, such as an apparent seasonal variation and a high intensity at frequencies between 3 and 4 mHz, were absent at the other SG stations. Among the SG stations used in this study, the background free oscillations were detected most consistently and distinctly at Canberra, where the noise level was comparable to that at the IDA quietest station, while that at Syowa Station was close to the critical limit for detecting the oscillations. The background free oscillations provide a good reference to evaluate the noise level in the milliHertz band. (C) 2000 Elsevier Science B.V. All rights reserved.
KW - Background free oscillations
KW - GEOSCOPE
KW - IDA
KW - Noise level
KW - SG
UR - http://www.scopus.com/inward/record.url?scp=0033915377&partnerID=8YFLogxK
U2 - 10.1016/S0031-9201(00)00158-8
DO - 10.1016/S0031-9201(00)00158-8
M3 - Article
SN - 0031-9201
VL - 120
SP - 289
EP - 297
JO - Physics of the Earth and Planetary Interiors
JF - Physics of the Earth and Planetary Interiors
IS - 4
ER -