Los Angeles:
Scientists say the massive earthquake that struck off the coast of Japan ranks as the fifth largest jolt in the world since 1900.
The magnitude-8.9 "megathrust" quake is similar to what happened during the 2004 Sumatra quake and the one last year in Chile. In all these cases, one tectonic plate is shoved beneath another.
Such earthquakes are responsible for the most powerful shifts in the Earth's crust.
More than 80 aftershocks greater than magnitude-5 have been felt since the Japanese quake - a number that scientists say is normal for a quake this size.
U.S. Geological Survey seismologist Lucy Jones said a friend who was in Tokyo for a tsunami planning meeting noted the shaking after the initial shock lasted for about five minutes.