Articles | Volume 10, issue 3
Nat. Hazards Earth Syst. Sci., 10, 581–588, 2010
https://doi.org/10.5194/nhess-10-581-2010
Nat. Hazards Earth Syst. Sci., 10, 581–588, 2010
https://doi.org/10.5194/nhess-10-581-2010

  26 Mar 2010

26 Mar 2010

The ionospheric perturbations associated with Asian earthquakes as seen from the subionospheric propagation from NWC to Japanese stations

Y. Kasahara2,1, F. Muto2,1, Y. Hobara2,1, and M. Hayakawa2,3 Y. Kasahara et al.
  • 1University of Electro-Communications (UEC), Department of Electronic Engineering, 1-5-1 Chofugaoka, Chofu Tokyo, 182-8585, Japan
  • 2UEC, Research Station on Seismo Electromagnetics, Chofu Tokyo, Japan
  • 3UEC, Advanced Wireless Communications Research Center, Chofu Tokyo, Japan

Abstract. Huge five earthquakes with magnitude greater than 6.0 took place in Asia (include Philippines, Indonesia, etc.) during the period from the beginning of August 2008 to the end of Junuary 2009, and the corresponding data of subionospheric VLF propagation between the NWC transmitter (Australia, 19.8 kHz) and a few Japanese stations (distance 6~8 Mm) are examined. As the result of our analysis by means of (1) trend (average nighttime amplitude), (2) dispersion, (3) nighttime fluctuation, and (4) atmospheric gravity wave enhancement, three earthquakes from the five taking place within the fifth Frenel zone are found to have accompanied a precursory signature in VLF propagation. On the other hand, there were observed no such precursory signatures for the remaing two earthquakes. One is too deep (>400 km) and another is too distant from the great-circle path. These characteristics of seismo-ionospheric perturbations would be of essential importance in studying the spatial/temporal properties of seismo-ionospheric perturbations for medium-distance propagation.

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