Earthquakes are caused by the cracking of the plates of rock (bedrock) that lie beneath the earth. Over time, forces build up on these rock plates and eventually they break. The force produced at that time is felt as an earthquake. The main reason for the plates to break is the movement of several large plates that cover the earth. These plates cover the surface of the earth and come in various sizes and shapes. When these plates collide or pass each other, earthquakes are likely to occur.
The Pacific Rim Seismic Zone, which encircles the Pacific Ocean, and the Himalayan-Alpine Seismic Zone, which extends from Indonesia through the Himalayas to the Mediterranean Sea. Japan is in the Pacific Rim seismic zone, and earthquakes occur frequently because of the movement of multiple plates beneath the ground. Depending on how these plates move, large and small earthquakes occur. Large earthquakes are especially likely to occur near deep ocean bottoms (ocean trenches). As the plates move, forces build up on land, which can also cause earthquakes.
