Tsunamis can be generated when the sea floor abruptly deforms and vertically displaces the overlying water . Tectonic earthquakes are a particular kind of earthquake that are associated with the Earth 's crustal deformation ; when these earthquakes occur beneath the sea , the water above the deformed area is displaced from its equilibrium position . More specifically , a tsunami can be generated when thrust faults associated with convergent or destructive plate boundaries move abruptly , resulting in water displacement , owing to the vertical component of movement involved . Movement on normal ( extensional ) faults can also cause displacement of the seabed , but only the largest of such events ( typically related to flexure in the outer trench swell ) cause enough displacement to give rise to a significant tsunami , such as the 1977 Sumba and 1933 Sanriku events
1977 Sumba
1977 Sumba earthquake
Tsunami