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Kan OKUBO Akihiro TAKEUCHI Yukinobu NAKAMURA Nobunao TAKEUCHI
The electric field mill in our underground observation room detected a co-seismic electromagnetic signal in the vertical electrostatic field ca. 8 s after the origin time of the Niigataken Chuetsu-oki Earthquake in 2007, but ca. 30 s before the arrival time of the P-waves.