To better understand the area where these recent earthquakes in Japan have been occurring, I want to explain the Ring of Fire in the Pacific. The Ring of Fire is an area in the Pacific Ocean basin where a large number of earthquakes and volcanoes eruptions occur. The Ring of Fire, 40,000 kilometers, has over 75% of the world's active and dormant volcanoes. About 80% of the world's largest earthquakes happen along the Ring of Fire. The Ring of Fire exists as a result of plate tectonics. Two tectonic plates are sliding against each other building up stress. The earth relieves the stress by slipping violently causing earthquakes and volcanic activity.
The Figure below shows the tectonic plates in the region.
The Nazca Plate and the Cocos Plate are being subducted underneath the South American Plate, which is moving to the west on the eastern side of the ring. The Cocos Plate is also being subducted beneath the Caribbean Plate. The Pacific Plate and the Juan de Fuca Plate are being subducted beneath the North American Plate. In the northern section of the ring, the Pacific plate, which is moving to the northwest, is being subducted underneath the Aleutian Islands arc and along the Kamchatka Peninsula arcs past Japan. In the south, there are a number of small plates colliding with the Pacific Plate.
For before and after pictures of Japan by moving your mouse over the picture click here.