Natural Hazards and Earth System Sciences (Jun 2011)

Daytime variations of foE connected to earthquakes

  • E. V. Liperovskaya,
  • V. V. Bogdanov,
  • P.-F. Biagi,
  • C.-V. Meister,
  • V. A. Liperovsky

DOI
https://doi.org/10.5194/nhess-11-1807-2011
Journal volume & issue
Vol. 11, no. 6
pp. 1807 – 1812

Abstract

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In the present work it is shown that, in accordance with the observations of the vertical sounding station "Tashkent", the critical foE-frequency of the daytime E-layer increases about one day before winter-earthquakes with magnitudes <i>M</i> > 5 and depths of the epicentre of <i>h</i> < 60 km, which appeared at distances of <i>R</i> < 2000 km from the station. The reliability of the result is larger than 99 %. The phenomenon is not observed for summer-earthquakes. It seems to be determined by the atmospheric wind system. Further, the variations of the foE-frequency are compared with possible simultaneous variations of the critical frequency foF2 of the F2-layer. First results show that only very large changes of the ionisation density in the E-layer influence the ionisation density in the F-region. Therefore, no synchronous growth of the foE- and foF2-frequencies 1–2 days before seismic shocks could be observed.