HR: 14:40h
AN: T43E-05 INVITED     [Abstracts]
TI: Identification of Earthquake Epicenter From Measurements of Electromagnetic Pulses in the Earth
AU: * Tsutsui, M
EM: tsutsui@cc.kyoto-su.ac.jp
AF: Department of Information and Communication Sciences, Kyoto Sangyo University, Kamigamo-Motoyama, Kita-ku, Kyoto, 603-8555 Japan
AB: More than twenty years, electromagnetic (EM) waves closely related to earthquakes have been examined by many scientists. However their source locations have remained unknown. Since 1999, we have been detecting EM pulses in the earth using an observation system constructed in the campus of Kyoto Sangyo University. An important part of the system is an electrically non-conductive borehole (10 cm in diameter and 100 m in depth). In these two years, we have developed a new system for finding arrival directions of EM pulses detected in the earth. A sensor system consisting of vertical dipole antenna and horizontally- and orthogonally-arranged two search coils was inserted into the borehole. Signals detected by the sensors are acquired into a personal computer as digital data, and are analyzed on real-time basis. The system detected an intense EM pulse just when an earthquake (M5.5) occurred at off Kii-peninsula in west Japan. In the analysis of the detected pulsed waveforms, we first derived frequency dispersion characteristic curves in order to provide amplitudes and relative phase relations among the detected signals for each frequency component contained in their pulses, because the amplitudes and phase relations among a vertical wave electric field E_v and the east-west and north-south components of horizontal wave magnetic field H_h can determine an arrival direction of the EM waves from the pointing vector E_v × H_h. Using these data, we obtained frequency-dependent arrival directions which made a sector shape on a map on the computer display. Among these many directions, an exact direction pointing toward the EM pulse source could be determined from arrival times of frequency components. Finally, we could find the source location of the EM pulse from estimations of its propagation distance as a waveguide mode, by means of comparison of the frequency dispersion curve with theoretical ones. The present measurement and analysis have shown that the source location of the EM pulse was just on the earthquake epicenter. From the result, we could manifest a positive causality between earthquakes and excitations of EM pulses
DE: 6914 Electromagnetic noise and interference
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
SC: Tectonophysics [T]
MN: Fall Meeting 2005