Anomalous ELF phenomena in the Schumann resonance band as observed at Moshiri (Japan) in possible association with an earthquake in Taiwan

Abstract

Abstract. The ELF observation at Moshiri (geographic coordinates: 44.29 • N, 142.21 • E) in Hokkaido, Japan, was used to find anomalous phenomena in the Schumann resonance band, possibly associated with a large earthquake (magnitude of 7.8) in Taiwan on 26 December 2006. The Schumann resonance signal (fundamental (n=1), 8 Hz; 2nd harmonic, 14 Hz, 3rd harmonic, 20 Hz, 4th, 26 Hz etc.) is known to be supported by electromagnetic radiation from the global thunderstorms, and the anomaly in this paper is characterized by an increase in intensity at frequencies from the third to fourth Schumann resonance modes mainly in the B EW component with a minor corresponding increase in the B N S component also. Spectral modification takes place only in the interval of 21:00 UT±1 h, which corresponds to the global lightning activity concentrated in America. While distortions were absent in other lightning-active UT intervals, in particular, around 08:00 UT±1 h (Asian thunderstorms) and around 15±1 h (African lightning activity). The anomaly occurred on 23 December three days prior to the main shock. The results observed were explained in terms of ELF radio wave perturbation caused by the lower ionospheric depression around the earthquake epicenter. The difference in the path lengths between the direct radio wave from an active global thunderstorm center and the wave scattered from the non-uniformity above Taiwan causes interference at higher resonance modes, which is successful in explaining the observational data.

Interpretation in terms of gyrotropic waves of Schumann-resonance-like line emissions observed at Nakatsugawa in possible association with nearby Japanese earthquakes

“…This kind of SR anomaly has been then confirmed by a statistical study of observation in Nakatsugawa for EQs with magnitude greater than 5.0 in Taiwan over a period of six years . Hayakawa et al (2008) have further confirmed the presence of similar SR higher mode enhancement at Moshiri, Japan, in possible association with the so-called Ping-tong EQ in Taiwan.…”

A Review of Low Frequency Electromagnetic Wave Phenomena Related to Tropospheric-Ionospheric Coupling Mechanisms

“…A correlation between ELF-VLF waves and earthquakes has been addressed by the seismology community. Employing statistical analyses, Hayakawa et al (1993Hayakawa et al ( , 2008 suggest anomalous effects in Schumann resonance spectra might be associated to earthquakes. They also claim that seismic activity modifies the rate and intensity of whistlers.…”

“…Nevertheless, ELF-VLF transient response due to earthquakes deserves further investigation. Anomalous effects in Schumann resonance phenomena possibly associated with earthquakes have been claimed (Hayakawa et al, , 2008. Even so, unambiguous causeeffect relation between Schumann resonance and earthquakes is difficult to establish because of the higher natural variability of lightning activity and of the ionosphere.…”

Localized ionospheric disturbance over the earthquake epicentre and modifications of Schumann resonance electromagnetic fields

“…Anomalous radio signals in the Schumann resonance (SR) band were reported for the first time in a series of works (Ohta et al 2001(Ohta et al , 2006Hayakawa et al 2005aHayakawa et al , 2008Hayakawa et al , 2010b. Analyses of the long-term SR records indicated that anomalies are usually observed in Japan when earthquakes (EQs) occur in Taiwan.…”