Many earthquakes happen on the ocean floor. Big ocean waves can form after a quake resulting in a tsunami.
The shaking of the ground is not what kills most victims of earthquakes. The main killers in earthquakes are falling buildings, fires, landslides, avalanches and tsunamis.
The deadliest known quake in history shook China in 1556, taking about 830,000 lives.
The 2004 earthquake that occurred in the Indian Ocean near Sumatra, Indonesia triggered a series of tsunamis that killed over 200000 people in 14 countries.