An attempt to delineate very low frequency electromagnetic signals associated with earthquakes

Abstract

We report on our observation of pulse-like electromagnetic signals in the frequency range 1∼10 kHz that we associate with earthquakes. The severest difficulty in separating earthquake-associated VLF signals from those originating in lightning discharges stems from the circumstance that the latter signals are overwhelming in number compared with the former. While claims have often been made of observation of electromagnetic signals in association with earthquakes, most of the claims, excepting a few, heavily rely on temporal correlation. By means of simple instrumentation and data processing software, our method by and large enables us to isolate VLF signals whose direction of arrival is well focussed at the epicenter direction. In this preliminary report we present several examples that positively demonstrate the existence of a class of VLF signals having a peak frequency of occurrence 1∼4 days prior to earthquakes of Magnitude 4∼6. With an accumulation of experience the technique described in this paper would seem to offer a promising approach towards earthquake prediction.

Influence of Lightning on the Observation of Seismic Electromagnetic Wave Anomalies

“…Recently, to remove the influence of lightning, Asada et al (2001) and Tsutsui (2005) adopted direction search and identification by waveform. They reported the possibility of the existence of VLF pulses transmitting from an epicenter before an earthquake.…”

“…For other earthquakes also, the increase in the number of electromagnetic pulses may be considered as due to lightning because the passage of low atmospheric pressure and lightning activities were reported within a distance of about 250 km from the observation station almost always when the increase was observed. Even if the seismic electromagnetic signals really existed, they would have been much weaker than those of lightning and difficult to identify (e.g., Asada et al 2001). (4) The results of the electromagnetic observation at our Uji station have been re-examined from the viewpoint of earthquake forecasting.…”

“…Though, Yoshino et al (1985), Asada et al (2001), andHattori (2004) detected that signals came from epicentral areas.…”

Statistical Mechanics and Information-Theoretic Perspectives on Complexity in the Earth System

“…From that time onwards, a large number of telluric current anomalies (e.g., [127,128]), ultra-low frequency (ULF) anomalies (e.g., [129][130][131][132][133]), very low frequency (VLF) to VHF anomalies (e.g., [133][134][135][136][137][138] and references therein), as well as a variety of atmospheric-ionospheric anomalies attributed to the phenomenon known as lithosphere-atmosphere-ionosphere (LAI) coupling (e.g., [124,[139][140][141][142] and the references therein) have been reported, analyzed and interpreted. More information, historical data and reviews can be found in [124,125,[143][144][145] and their references.…”

VHF-electromagnetic evidence of the underlying pre-seismic critical stage

“…We note that recently, Asada et al (2001) have presented an attempt to delineate VLF (1 ∼ 10 kHz) EM signals associated with EQs. The association of the VLF emissions with the occurrence of an EQ is inferred from (a) temporal correlation and (b) agreement between the direction of VLF signal arrival and that epicentre.…”