Day- time variations of foF2 connected to strong earthquakes.

LIPEROVSKAYA E.V.1, LIPEROVSKY V.A.1, BOGDANOV V.V.2, BIAGI P.-F.3, MEISTER C.-V.4, RODKIN M.V.5
  1. Institute of Physics of the Earth, Russian Academy of Sciences
  2. Institute of Cosmophysical Research and Radio Wave Propagation, Far Eastern Branch, Russian Academy of Sciences
  3. Physics Department, University of Bari
  4. Technische Universität Darmstadt, Institut für Kernphysik
  5. Geophysical Centre of the Russian Academy of Sciences

The statistical analysis of the characteristic frequency foF2 of the Earth's ionosphere averaged over midday hours - from 11:00 till 17:00hLT - is carried out. Disturbances of foF2 connected to earthquakes are considered on the background of seasonal, geomagnetic, 11-years and 27-days solar variations. A special normalized parameter F is introduced, which represents the almost seasonal-independent part of foF2. Days with high solar (Wolf number>100) and geomagnetic (£Kp>30) activity are excluded from the analysis. Events with magnitude M>5, distance from the sounding station R<500km and depth h<70 km are taken into account. The superimposed epoches' method is used to determine the temporal dependence of F. It is found that F increases about 3-6 days before the earthquakes and then decreases one day - two days before the shock. The decreased values of F continue to exist two-three days after events with M>5.5. The obtained phenomenon depends on the magnitude of the earthquake. For events with M>5.5, the reliability of the effect is larger than 95%. For data of more than 80 earthquakes in the vicinity of Petropavlovsk-Kamchatsky and more than 200 earthquakes in the vicinity of Tokyo analogous results are obtained.

 

LIPEROVSKAYA E.V., LIPEROVSKY V.A., BOGDANOV V.V., BIAGI P.-F., MEISTER C.-V., RODKIN M.V. Day- time variations of foF2 connected to strong earthquakes. // Natural Hazards and Earth System Sciences. 2009. V.9, №1.P.53-59/