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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy (S) - IASPEI - International Association of Seismology and Physics of the Earth's Interior JSS008 Oral Presentation 1993 Electromagnetic wave Anomaly of Earthquake and Signal Processing to Detect Precursor Prof. Masayasu Hata Computer Science Div. Chubu University IASPEI Takashi Fujii, Ichi Takumi, Hirosi Yasukawa We have been studying an earthquake precursor of environmental electromagnetic waves (EM) at ELF band of 30-300Hz for the last twenty years. The observed signals contain local anomalous radiation of earthquakes as well as global background noise due to tropical thunderstorm. The global noise distorts the earthquake prediction. A method of global noise elimination is discussed by Independent Component Analysis (ICA). The second signal processing is to extract a precursor relevant to earthquake. For the processing, the linear predicting coefficient (LPC) method is applied. The LPC error was well acknowledged as a precursor of earthquakes exceeding magnitude five. In the paper, a new approach to extract precursor out of noisy ELF environmental signal by making use of Linear Predicting Coefficient, LPC signal model is introduced. For the case of Off-West-Fukuoka earthquake with M7.0, an anomalous magnetic flux radiation of about 10pT/√Hz with 1pT/√Hz background noise was detected about four days before the event at Tijiwa town Nagasaki Prefecture, 120km south of the epicenter, and five aftershocks exceeding M5.0 also followed respectively the anomalous radiations within one days delay. The radiation area was determined near the epicenter for both the main and aftershocks, by direction finding of the detected anomaly signal from two sites of Tijiwa and Tomochi through the signal amplitude ratio of EW to NS of sensing loop coils. These two facts may confirm the existence of EM precursor. Keywords: electromagneticwave anomaly, elf band, lpc
IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy (S) - IASPEI - International Association of Seismology and Physics of the Earth's Interior JSS008 Oral Presentation 1994 Magnetotelluric survey around source region of the 2003 Tokachi-Oki earthquake Prof. Toru Mogi Institute of Seismology and Volcanology Hokkaido University IAGA Kengo Tanimoto, Yusuke Yamaya, Hiroyuki Kamiyama, Takeshi Hashimoto, Venera Doblica, Takanori Kajiwara, Makoto Uyeshima, Yasuo Ogawa The 2003 Tokachi-oki earthquake (Mw=8.0) occurred at 26th September. The hypocenter was determined at 80 km off of the Erimo area, the southern part of Hokkaido, Northern Japan. The source region, including the asperity and aftershock region, spread to about 100km wide in NW and NE direction over the upper plane of the Pacific plate. The lower edge of the source region reached beneath the Erimo area at a depth of 50km. The Pacific plate is subducting at rate of about 8 cm/year to the NW direction beneath Hokkaido along the Japan-Kuril trench, a depth of about 6000m, situated at 100km off from the land. We carried out wide band magentotelluric survey, covered frequency range over 320 to 0.8x10-4 Hz, at 25 sites in the Erimo area to clarify the resistivity structure of the source region. The sites were arrayed in a grid in about 50x50 km area, and the site array enables us to construct threedimensional resistivity model. The survey area faced to Pacific Ocean and the data obtained at the coast area were seriously affected by a sea effect. We are constructing three dimensional resistivity model including sea to become reality. The resistivity structure reveals resistive subducting plate at deeper part of the area and its complex shape in this area. Keywords: magnetotellluric, resistivity
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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy<br />
(S) - <strong>IASPEI</strong> - International Association of Seismology and Physics of the Earth's<br />
Interior<br />
JSS008 Oral Presentation 1994<br />
Magnetotelluric survey around source region of the 2003 Tokachi-Oki<br />
earthquake<br />
Prof. Toru Mogi<br />
Institute of Seismology and Volcanology Hokkaido University IAGA<br />
Kengo Tanimoto, Yusuke Yamaya, Hiroyuki Kamiyama, Takeshi Hashimoto, Venera<br />
Doblica, Takanori Kajiwara, Makoto Uyeshima, Yasuo Ogawa<br />
The 2003 Tokachi-oki earthquake (Mw=8.0) occurred at 26th September. The hypocenter was<br />
determined at 80 km off of the Erimo area, the southern part of Hokkaido, Northern Japan. The source<br />
region, including the asperity and aftershock region, spread to about 100km wide in NW and NE<br />
direction over the upper plane of the Pacific plate. The lower edge of the source region reached beneath<br />
the Erimo area at a depth of 50km. The Pacific plate is subducting at rate of about 8 cm/year to the NW<br />
direction beneath Hokkaido along the Japan-Kuril trench, a depth of about 6000m, situated at 100km<br />
off from the land. We carried out wide band magentotelluric survey, covered frequency range over 320<br />
to 0.8x10-4 Hz, at 25 sites in the Erimo area to clarify the resistivity structure of the source region. The<br />
sites were arrayed in a grid in about 50x50 km area, and the site array enables us to construct threedimensional<br />
resistivity model. The survey area faced to Pacific Ocean and the data obtained at the coast<br />
area were seriously affected by a sea effect. We are constructing three dimensional resistivity model<br />
including sea to become reality. The resistivity structure reveals resistive subducting plate at deeper<br />
part of the area and its complex shape in this area.<br />
Keywords: magnetotellluric, resistivity
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