Just below the surface of the earth lie huge sheets of rock called tectonic plates that are about 70 kilometers thick. When the distortions get large enough, forces try to correct them, causing the plates to move suddenly. Earthquakes are the results of the shaking that occurs then.
Earthquakes are most frequent where two or more plates meet.
The reason Japan has so many earthquakes is because a number of these plates converge below the country's surface. The Kobe Earthquake of January 1995 took a heavy toll of human lives and property. To lighten the damage earthquakes inflict in the future, scientists are studying ways to predict the occurrence of quakes more accurately and to construct buildings that are more resistant to quakes. Many local governments have adopted disaster-prevention measures. Shizuoka Prefecture, which faces the Pacific Ocean and is thought to be a candidate for a large quake in the near future, has adopted an earthquake-prevention plan that outlines the steps that should be taken in case a major earthquake strikes, including the regulation of traffic, closing of banks and department stores, and evacuation of residents.