Suchergebnisse

Abstract. The recent results of the research for earthquake precursory phenomena on the underground water level and temperature at the area Pieria of northern Greece are presented. The analysis of our observations in relation to the local microseismicity indicate that underground water level variations may be considered as precursory phenomena connected to the local microseismic activity in the area of Pieria. Base on these results, it can be supported that monitoring the shallow underground water level and temperature for detecting earthquake precursory phenomena may be proved to be a useful method in the framework of an interdisciplinary research for earthquake prediction.

Abstract. Changes of barometric pressure in the area of Thessaloniki in Northern Greece were studied by analyzing a sample of 31 years of hourly measurements. The results of this analysis on the periodicities of tidal components are expressed in terms of amplitude and phases variability. An earlier investigation revealed a detectable correlation between the exalting of the amplitude parameters of the tidal waves with strong seismic events. A problem of this work was that we had compared the tidal parameters resulting from the analysis of data covering the period of one year with instantaneous seismic events, although the earthquake is the final result of a tectonic process of the upper lithosphere. Consequently, in order to increase the resolution of our method we had analyzed our data in groups of 3-months extent and the resulted amplitudes were compared with seismicity index for corresponding time periods. A stronger correlation was found in the last case. However, the estimation of tidal parameters in this case was restricted to short period (from one day down to eight hours) constituents. Therefore, a new analysis was performed, retaining the one-year length of each data block but shifting the one year window by steps of three months from the beginning to the end of the 31 years period. This way, we are able to estimate again tidal parameters ranging from periods of one year (Sa) down to eight hours (M3). The resulting correlation between these tidal parameters with a cumulative seismicity index for corresponding time intervals was remarkably increased.

Abstract. 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.

Abstract. In this paper the Total Electron Content (TEC) data of eight Global Positioning System (GPS) stations of the EUREF network (AUT1, Thessaloniki, TUC2, Crete in Greece, MATE, Matera, LAMP, Lampedusa in Italy, GAIA, in Portugal, RABT, Rabat, EVPA, Evpatoria in Ukrain and TRAB, Trabson in Turkey) were analysed using wavelet analysis in order to detect any frequency dependence of the correlation between TEC over different stations. In the same time frequency dependence of Dst (Global geomagnetic field disturbances) and TEC variations over each GPS station are searched in order to detect any correlation between them. The main conclusion of this analysis is that the components of TEC variation with periods <3 h are more suitable in searching for earthquake precursors. On the base of this conclusion the analyzed TEC series are searched for possible precursory phenomena on the occasion of the seismic activity of the last quarter of 2005 in the area of Greece. An exalting (i.e. an increase in the amplitude) of variations with periods up to the tidal ones (period of 6 h,8 h,12 h) may be observed a month before and during the seismic activity over the stations TUC2 and AUT1 and may be attributed to this tectonic activity. Statistical properties of the 1.5 h component of the Total Vertical Electron Content (TVEC) over the nearest GPS stations (TUC2 and AUT1) of the areas of the seismic activity indicate that this component present characteristic exalting in the time period of 15 days before the shock.