“I. Initiation: Earthquakes are commonly associated with ground shaking that is a result of elastic waves traveling through the solid earth. However, near the source of submarine earthquakes, the seafloor is "permanently" uplifted and down-dropped, pushing the entire water column up and down. The potential energy that results from pushing water above mean sea level is then transferred to horizontal propagation of the tsunami wave (kinetic energy). For the case shown in the slide, the earthquake rupture occurred at the base of the continental slope in relatively deep water. Situations can also arise where the earthquake rupture occurs beneath the continental shelf in much shallower water.

Note: In the figure the waves are greatly exaggerated compared to water depth! In the open ocean, the waves are at most, several meters high spread over many tens to hundreds of kilometers in length.”

Citation source:http://www.owlnet.rice.edu/~esci108/108_EQ_Lec_4.ppt