There may be as many as a million earthquakes in a single year. Most of them take place beneath the surface of the sea. Comparatively few of these cause any damage. But earthquakes that occur near large cities cause much damage and loss of life. The energy released by a large earthquake may be equal to about 2,000,000,000 tons of TNT, or 10,000 times more than the first atomic bomb.
Large earthquakes cause violent motions of the earth's surface.
Sometimes they cause huge sea waves to sweep up on land and add to the general destruction. Such waves often occur in the Pacific Ocean, because of earthquakes within ocean basins. The Japanese call these destructive waves tsunami. The most notable earthquakes, are two of the biggest, San Francisco and great Alaska earthquake, Mexico and Armenia, Turkey, Japan have all had massive quakes. Here in California, I have experienced some pretty big quakes.