Why was Japan's March 11 earthquake so big? One answer is the large size of the fault rupture as well as the speed at which the Pacific Plate is continuously thrusting beneath Japan, U.S. Geological Survey (U.S.G.S.) scientist Tom Brocher told KQED News. People felt shaking in cities all over Honshu, Japan's main island.
Below are some more facts and figures relating to the causes and consequences of the world's fifth-largest earthquake since 1900.
Magnitude, according to USGS: 9.0
Speed at which the Pacific Plate is smashing into the Japanese island arc: 6 centimeters (3.5 inches) per year
Speed at which the San Andreas Fault in California is slipping: about 4 centimeters per year
Size of the rupture along the boundary between the Pacific and North America plates: 290 kilometers ( 180 miles) long, 80 kilometers (50 miles) across
Approximate length of Honshu island: 1,300 kilometers
Years since an earthquake of this magnitude has hit the plate boundary of Japan: 1,200
Duration of strong shaking reported from Japan: 3 to 5 minutes
Greatest distance from epicenter that visitors to the USGS Web site reported feeling the quake: About 2,000 kilometers
Distance that the island of Honshu appears to have moved after the quake: 2.4 meters
Change in length of a day caused by the earthquake's redistribution of Earth's mass: 1.8 microseconds shorter
Normal seasonal variation in a day's length: 1,000 microseconds
Depth of the quake: 24.4 kilometers
Range of depths at which earthquakes occur in Earth's crust: 0 – 700 kilometers
Top speed of tsunami waves over the open ocean: About 800 kilometers per hour
Normal cruising speed of a jetliner: 800 kilometers per hour
Length of warning time Sendai residents had before tsunami hit: 8 to 10 minutes
Number of confirmed foreshocks to the main shock: 4
Magnitudes of the confirmed foreshocks: 6.0, 6.1, 6.1 and 7.2
Number of confirmed aftershocks: 401
Worldwide average annual number of earthquakes over 6.0 in magnitude: 150
From Scientific American. More Here.