A novel method called Generalized Average of Signals (GAS) for detection of very weak waves in seismograms is describe d and tested. The general principle of the GAS method is to take advantage of the cohe rency of the signal, which is extracted. The signals are shaped with moving window and converted to the frequency domain. Then they are non-linearly summed considering their complex representation (a mplitudes and phases). The method impr oves signal-to-noise ratio of coherent seismograms considerably. The GAS method is tested on sy nthetic seismograms and comp ared with the PWS method., Jiří Málek, Petr Kolínský, Jaroslav Štrunc and Jan Valenta., and Obsahuje bibliografické odkazy