Earthquake :
An earthquake (also known as a quake, tremor or temblor) sudden movement of the earth’s outer layer caused by the discharge of stress mounts up along geologic faults or by volcanic activity.
The highest magnitude 9.0 Tohoku earthquake on March 11, 2011, which occurred near the northeast coast of Honshu, Japan, resulted from thrust faulting on or near the subduction zone plate border between the Pacific and North America plates. At the latitude of this earthquake, the Pacific plate travels approximately westwards with respect to the North America plate at a rate of 83 mm/yr and started on its westward descent beneath Japan at the Japan Trench. Many people divide this region into several microplates that together define the relative motions between the larger Pacific, North America and Eurasia plates; these consist of the Okhotsk and Amur microplates that are respectively part of North America and Eurasia.
The March 11 earthquake was leaded by a series of large foreshocks over the previous two days, beginning on March 9th with a M 7.2 event approximately 40 km from the epicenter of the March 11 earthquake, and continuing with another three earthquakes greater than M 6 on the same day.
Causes for Earthquake in Japan :
The Japanese archipelago is situated in an area where some continental and oceanic plates meet up. This is the main reason of frequent earthquakes and also the presence of many volcanoes and hot springs crossways Japan. If earthquakes take place under or close to the ocean, they may generate tidal waves (tsunami).
The terribly violent earthquake in Japan is being called the largest in the country's "recorded history." Many divisions of the country have experienced devastating major earthquakes and tidal waves in the past. The Great Kanto Earthquake, the most terrible in Japanese history, hit the Kanto plain, Hyogo Earthquake in Kobe and so on.
