2004 Fiscal Year Final Research Report Summary
Observations of CD-seismic Electromagnetic Phenomena in VHF Band
| Project/Area Number |
14550367
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
情報通信工学
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| Research Institution | Hiroshima City University |
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Principal Investigator |
YOSHIDA Teruaki Hiroshima City University, Faculty of Information Sciences, Professor, 情報科学部, 教授 (50316139)
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| Co-Investigator(Kenkyū-buntansha) |
NISHI Masahiro Hiroshima City University, Faculty of Information Sciences, Associate Professor, 情報科学部, 助教授 (30316137)
HATSUDA Takeshi Hokkaido Institute of Technology, Faculty of Engineering, Professor, 工学部, 教授 (10198757)
KAGOSHIMA Kenichi Ibaraki University, Faculty of Engineerings, Professor, 工学部, 教授 (70292472)
OGOSE Shigeki Ibaraki University, Faculty of Engineerings, Associate Professor, 工学部, 助教授 (50323209)
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| Project Period (FY) |
2002 – 2004
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| Keywords | Co-seismic Electromagnetic Phenomena / VHF band / Radio Propagation / Dual Frequency Method / Ionospheric reflection / Tropospheric duct |
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| Research Abstract |
1)Observation system
In our investigation, the observation of seismic electromagnetic phenomena have been conducted to solve these following subjects. 1.Does electromagnetic phenomena associated with EQ occur? 2.Does the EQ make the ionospheric layer reflect the FM broadcasting waves? To realize our observation, we have constructed the VHF band observation systems. The feature of our observation system is as followings.
- Observation in FM broadcasting band : This band is hardly influenced by artificial or urban noises.
- Dual Frequency Observation : To distinguish the seismic broadband phenomena from FM broadcasting waves, we have developed a novel dual frequency observation method in which the observation is made attwo different frequencies
- Observation using digital FM tuner : This tuner has high frequency selectivity and stability, and thequantitative observation can be realized.
(2)Observation results
1.Observation of seismic electromagnetic phenomena
We could observe the seismic phenom
… More
ena in Geiyo EQ (2001), Ibaraki-ken-oki EQ (2002), and Niigata-ken
Chuetsu EQ (2004). In these EQ, the broadband electromagnetic waves were observed. And it is found that these observed electromagnetic waves are generated from the seismic swing of the land near the observation site. Moreover, the other EM phenomenon detected in VHF band disappeared at the time of earthquake. Amplitude fluctuations of about 2 dB were observed since one day before the Geiyo EQ, then, the fluctuations disappeared at the occurrence of EQ.
2.Observation of long-distance FM broadcasting propagation
The 77.1 MHz FM broadcasting wave from Sendai has been observed in Ibaraki observation site. From this observation, it is found that the FM broadcasting wave propagates in the tropospheric duct or on the geosphere. Our observation results show that the EQ hardly influence the ionospheric layer to reflect the FM broadcasting waves at the occurrence of EQ.
(3)Improvement of observation system.
Especially in the high electric field strength, the BPF should be inserted to reduce the intermodulation distortion. Less
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