Underground Electric Signal at the Occurrence of the Niigataken Chuetsu-oki Earthquake in 2007, Japan

摘要

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.