Detections of electromagnetic waves excited by earthquakes

In ELF range, we finally detected electromagnetic (EM) pluses directly excited by earthquakes in a deep borehole. By simultaneous capturing of waveforms of magnetic component of the EM pulses and of seismic waves measured at the EM observation site, we have confirmed that seismic P-wave readily excited EM waves. The result suggests that EM waves were very sensitive to the vibrations of seismic waves. Clear difference of fluctuating periods between EM waves and seismic waves has proved that the EM signal was just the result of detections of EM fields excited due to the Piezo-electric effect, but was not induced due to relative movement of electrically conductive earth´s medium swayed by the earthquake against magnetic search coils. We also found that EM pulses excited by seismic waves have leaked out of the ground surface.