Extracting preseismic electric signals from noisy Earth's electric field   data recordings. The "noise injection" method
  An entirely different approach is used for the extraction of preseismic electric signals from highly contaminated by noise data series. The basic element of this method is the "Dirac Delta Function". Noise is injected, instead of applying any known method of filtering, in the data series at different amplitude levels (p value) and the generated "family" of filtered data series is compared to different convergence criteria. In the case of preseismic electric signals identification the most appropriate (p) value is selected by testing the convergence of generated intersections of more than three "families" of filtered data which were generated from more than three monitoring sites. The "noise injection" method was tested against real data recorded long before two large earthquakes in Greece and one in Turkey. 
C. Thanassoulas, V. Klentos, G. Verveniotis