Pre-Seismic Electrical Signals (SES) generation and their relation to   the lithospheric tidal oscillations K2, S2, M1 (T = 12hours / 14 days)
  It is postulated that the preseismic electric signals (SES) are generated by the piezoelectric mechanism applied on small rock grains - blocks during their stress load until fracturing. Specifically, the square electric train pulses are generated by the combination of a stress increase phase which generates a positive piezostimulated polarized current pulse (PSPC) followed, in a short time, by the stress decrease phase at fracturing level which generates a negative piezostimulated depolarized current pulse (PSDC). Moreover, it is shown that the SES signals are closely related to the tidally triggered lithospheric stress maxima - minima. Examples of SES signals are presented in relation to the tidally triggered lithospheric oscillation (k2, S2, M1) of T = 12hours / 14 days, while some comments are made as far as it concerns their use in short-term earthquake prediction. 
Constantine Thanassoulas