Carter B. A., A. C. Kellerman, T. A. Kane, P. L. Dyson, R. Norman, K. Zhang, (2013), Ionospheric precursors to large earthquakes: A case study of the 2011 Japanese Tohoku Earthquake, Journal Of Atmospheric And Solar-terrestrial Physics, 102, 290 – 297, doi:10.1016/j.jastp.2013.06.006

Abstract

Researchers have reported ionospheric electron distribution abnormalities, such as electron density enhancements and/or depletions, that they claimed were related to forthcoming earthquakes. In this study, the Tohoku earthquake is examined using ionosonde data to establish whether any otherwise unexplained ionospheric anomalies were detected in the days and hours prior to the event. As the choices for the ionospheric baseline are generally different between previous works, three separate baselines for the peak plasma frequency of the F2 layer, foF2, are employed here; the running 30-day median (commonly used in other works), the International Reference Ionosphere (IRI) model and the Thermosphere Ionosphere Electrodynamic General Circulation Model (TIE-GCM). It is demonstrated that the classification of an ionospheric perturbation is heavily reliant on the baseline used, with the 30-day median, the IRI and the TIE-GCM generally underestimating, approximately describing and overestimating the measured foF2, respectively, in the 1-month period leading up to the earthquake. A detailed analysis of the ionospheric variability in the 3days before the earthquake is then undertaken, where a simultaneous increase in foF2 and the Es layer peak plasma frequency, foEs, relative to the 30-day median was observed within 1h before the earthquake. A statistical search for similar simultaneous foF2 and foEs increases in 6years of data revealed that this feature has been observed on many other occasions without related seismic activity. Therefore, it is concluded that one cannot confidently use this type of ionospheric perturbation to predict an impending earthquake. It is suggested that in order to achieve significant progress in our understanding of seismo-ionospheric coupling, better account must be taken of other known sources of ionospheric variability in addition to solar and geomagnetic activity, such as the thermospheric coupling.

Authors (sorted by name)

Carter Dyson Kane Kellerman Norman Zhang

Journal / Conference

Journal Of Atmospheric And Solar-terrestrial Physics

Acknowledgments

This research was supported by the Australian Space Research Program project endorsed to a research consortium led by K. Zhang at RMIT University. The Japanese ionosonde data were collected by and obtained from the World Data Center for Ionosphere, Tokyo, National Institute of Information and Communications Technology, http://wdc.nict.go.jp. The geomagnetic and solar activity data were obtained from the OMNIWeb Plus website, http://omniweb.gsfc.nasa.gov. Fruitful discussions with P. Wilkinson and M. Francis are kindly acknowledged.

Bibtex

@article{CARTER2013290,
title = "Ionospheric precursors to large earthquakes: A case study of the 2011 Japanese Tohoku Earthquake",
journal = "Journal of Atmospheric and Solar-Terrestrial Physics",
volume = "102",
pages = "290 - 297",
year = "2013",
issn = "1364-6826",
doi = "10.1016/j.jastp.2013.06.006",
url = "http://www.sciencedirect.com/science/article/pii/S136468261300182X",
author = "B.A. Carter and A.C. Kellerman and T.A. Kane and P.L. Dyson and R. Norman and K. Zhang",
keywords = "Ionospheric precursors, Ionosphere variability, Earthquake prediction",
abstract = "Researchers have reported ionospheric electron distribution abnormalities, such as electron density enhancements and/or depletions, that they claimed were related to forthcoming earthquakes. In this study, the Tohoku earthquake is examined using ionosonde data to establish whether any otherwise unexplained ionospheric anomalies were detected in the days and hours prior to the event. As the choices for the ionospheric baseline are generally different between previous works, three separate baselines for the peak plasma frequency of the F2 layer, foF2, are employed here; the running 30-day median (commonly used in other works), the International Reference Ionosphere (IRI) model and the Thermosphere Ionosphere Electrodynamic General Circulation Model (TIE-GCM). It is demonstrated that the classification of an ionospheric perturbation is heavily reliant on the baseline used, with the 30-day median, the IRI and the TIE-GCM generally underestimating, approximately describing and overestimating the measured foF2, respectively, in the 1-month period leading up to the earthquake. A detailed analysis of the ionospheric variability in the 3days before the earthquake is then undertaken, where a simultaneous increase in foF2 and the Es layer peak plasma frequency, foEs, relative to the 30-day median was observed within 1h before the earthquake. A statistical search for similar simultaneous foF2 and foEs increases in 6years of data revealed that this feature has been observed on many other occasions without related seismic activity. Therefore, it is concluded that one cannot confidently use this type of ionospheric perturbation to predict an impending earthquake. It is suggested that in order to achieve significant progress in our understanding of seismo-ionospheric coupling, better account must be taken of other known sources of ionospheric variability in addition to solar and geomagnetic activity, such as the thermospheric coupling."
}