Natural Hazards and Earth System Science www.nat-hazards-earth-syst-sci.net 1561-8633 1684-9981 4 1 2004 10.5194/nhess-4-1-2004 http://www.nat-hazards-earth-syst-sci.net/4/1/2004/ http://www.nat-hazards-earth-syst-sci.net/4/1/2004/nhess-4-1-2004.html http://www.nat-hazards-earth-syst-sci.net/4/1/2004/nhess-4-1-2004.pdf 1 7 2004-03-01 Atmospheric tide disturbances as Earthquake precursory phenomena D. N. Arabelos G. Asteriadis A. Bloutsos M. E. Contadakis S. D. Spatalas Department of Geodesy and Surveying, Aristotle University of Thessaloniki, Greece Department of Meteorology and Climatology, Aristotle University of Thessaloniki, Greece The tidal changes of the barometric pressure in the area of Thessaloniki were studied by analysing a sample of 21 years of hourly measurements. The resulted tidal parameters (amplitude and phase difference) were considered as "mean values" of the corresponding parameters for this long time period. Using these parameters, barometric changes were computed and subtracted from the observations. Assuming that the residuals might include local (in terms of time) information,the residual time series was split in 21 blocks and a new analysis was performed for each block separately. The 21 amplitude values computed for each tidal wave were considered as the amplitude variation with respect to the correspondingmean value. An observable correlation of the amplitude exalting of the most of the tidal waves was found to Earthquakes of magnitude >4, occurred close to Thessaloniki in the test period.