Electromagnetic Observations of the Earthquake Occurred in Sendai City

Abstract

We observed the coseismic electromagnetic phenomena at the occurrence of the earthquake in Sendia City area. This earthquake's epicenter was very close, less than 10km from our observation site. Our site accidentally located on the fault of which the underground tip slid at the focus. In addition to variations of the earth potential difference and the ground acceleration signals, we observed the clear variations of the ground ion concentration and the geomagnetic field signals. We cannot yet explain the cause how these variations appear and what conditions are needed to observe always these variations. More events are needed to make this clear and the observation must be continued.