Anomalous excitation of Schumann resonances and additional anomalous resonances before the 2004 Mid-Niigata prefecture earthquake and the 2007 Noto Hantou Earthquake

Abstract

We have carried out the observation of ULF/ELF electromagnetic waves below 50 Hz at Nakatsugawa (in Gifu Prefecture in Japan) with three component induction coil antennas (the permalloy of 1.2 m length with 1,00,000 turns of the copper wire) since 1998. We have observed the excitation of anomalous resonances possibly associated with earthquakes at Nakatasugawa station. In this paper, we analyzed the anomalous strong Schumann resonance and an additional anomalous resonance observed before the 2004 Mid-Niigata Prefecture earthquake and the 2007 Noto Hantou earthquake. The intensity of a particular mode of the Schumann resonance increased before the large earthquake near the observation station, and decreased after the occurrence of earthquake. An excitation of another anomalous resonance was also observed at the frequency shifted by about 2 Hz from the typical frequency of the Schumann resonance. Since the temporal changes of the intensity of the anomalous Schumann resonance and another excited anomalous resonance were almost the same, there is a possibility that another anomalous resonance was related with the Schumann resonance. However, we need to consider a more convincible generation mechanism of anomalous resonances.