Total electron content variations over southern Europe before and during the M 6.3 Abruzzo earthquake of April 6, 2009

Total electron content (TEC) data of 14 global positioning system (GPS) stations of the EUREF network were provided by the IONOLAB. These were analyzed using wavelet analysis and discrete Fourier analysis to investigate the TEC variations over southern Europe in the month before the catastrophic Abruzzo earthquake of M 6.3 of April 6, 2009. The main conclusions of this analysis are: (a) TEC oscillations in a broad range of frequencies occurred randomly over a broad area of several hundred kilometers from the earthquake; (b) Morning and evening extensions of the day-time TEC values were seen for all of the EUREF stations of this program shortly before, during and shortly after the main earthquake period; (c) High frequency oscillations (f >= 0.0003 Hz, period T >= 60 m) appear to indicate the location of the earthquake, although with questionable accuracy, while the fractal characteristics of the frequency distribution indicates the locus of the earthquake with relatively greater accuracy. We conclude that the lithosphere-atmosphere-ionosphere coupling mechanism through acoustic or gravity waves might explain this phenomenology.