Incessant excitation of the Earth's free oscillations

被引:120
|
作者
Nawa, K [1 ]
Suda, N
Fukao, Y
Sato, T
Aoyama, Y
Shibuya, K
机构
[1] Nagoya Univ, Dept Earth & Planetary Sci, Chikusa Ku, Nagoya, Aichi 4648602, Japan
[2] Univ Tokyo, Earthquake Res Inst, Bunkyo Ku, Tokyo 1130032, Japan
[3] Natl Astron Observ, Mizusawa, Iwate 0230861, Japan
[4] Grad Univ Adv Studies, Mizusawa, Iwate 0230861, Japan
[5] Natl Inst Polar Res, Itabashi Ku, Tokyo 1730003, Japan
来源
EARTH PLANETS AND SPACE | 1998年 / 50卷 / 01期
关键词
D O I
10.1186/BF03352080
中图分类号
P [天文学、地球科学];
学科分类号
07 ;
摘要
We, for the first time, report the evidence of incessant excitation of the Earth's free oscillations, mainly the fundamental spheroidal modes in a frequency range from 0.3 to 5 mHz, based on the three year record of a superconducting gravimeter at Syowa Station, East Antarctica. The frequency-time spectrogram of this record is striped by more than 30 lines at nGal level parallel to the time axis, mostly corresponding to the fundamental spheroidal modes. This spectrogram is characterized by relatively efficient excitation of gravest fundamental modes, enhancement of signal intensities in the austral winter and amplification of signal in the frequency band from 3 to 4 mHz. Assuming that earthquakes are only the sources for the free oscillations, we calculate the synthetic spectrograms, which have not shown such a series of parallel lines as observed. The result of this synthetic test and characteristics of the observed spectrogram suggest that the mode signals we found are not of earthquake origin. We tentatively suggest atmospheric or oceanic origin for this newly discovered phenomenon of the solid Earth.
引用
收藏
页码:3 / 8
页数:6
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