Tsunamis are not just large waves: they are generated by vertical displacement of sea water by some kind of submarine activity. A tsunami is in fact a series of waves with a very long wavelength (the distance between one wave and the next) and long wave period (time between waves). read more
Earthquakes trigger tsunamis when the seismic activity causes the land along fault lines to move up or down. When parts of the seafloor shift vertically, either becoming raised or lowered, entire water columns become displaced. This creates a"wave" of energy, which propels the water, according to Blakeman. read more