Seminar Series of Active Geosphere # 18: 27 April, 2005
by Dr. T. Iyemori (1), M. Nose (1), D.-S. Han (1,6), M. Hashizume (2), Y.-F. Gao (4), H. Shinagawa (3), Y. Tanaka (1), A. Saito (1), H. McCreadie (1), M. Choosakul (2), M. Utsugi (1), F. Yang (5)
Affiliations: (1) Graduate School of Science, Kyoto University, (2) Faculty of Science, Chulalongkorn University, (3) STE Laboratory, Nagoya University, (4) Institute of Geophysics, China Earthquake Administration, (5) Xinjiang Seismological Bureau, (6) Polar Research Institute of China
"Geomagnetic pulsations observed at Sumatra earthquake"
A magnetic pulsation with a period about 3.6 minutes was observed at Phimai
(15.2N, 102.6E)12 minutes after the origin time of Sumatra earthquake on
December 26. At Tong Hai (24.0N, 102.7E) in China, 10 degrees north in
latitude, only a short period (i.e., about 30 seconds) magnetic pulsation
was observed. At higher latitudes, no magnetic pulsation with these periods
was observed. It is clear that the oscilation is not the effect of sensor
oscillation, because of the timing relation between the origin time of the
earthquake and the onset time of magnetic pulsation, and also because of the
amplitude relation among magnetic components. The localized nature and
oscillation period suggest that this magnetic pulsation was generated with a
dynamo in the ionosphere caused by acoustic duct resonance between sea
surface (or middle atmosphere) and bottom of the thermosphere.