Earthquake Facts

Photo courtesy NGDC
Residential damage in Prince William Sound, Alaska, due to liquefaction caused by a 1964 9.2-magnitude earthquake.

We only hear about earthquakes in the news every once in a while, but they are actually an everyday occurrence on our planet. According to the United States Geological Survey, more than three million earthquakes occur every year. That's about 8,000 a day, or one every 11 seconds!

The vast majority of these 3 million quakes are extremely weak. The law of probability also causes a good number of stronger quakes to happen in uninhabited places where no one feels them. It is the big quakes that occur in highly populated areas that get our attention.

Earthquakes have caused a great deal of property damage over the years, and they have claimed many lives. In the last hundred years alone, there have been more than 1.5 million earthquake-related fatalities. Usually, it's not the shaking ground itself that claims lives -- it's the associated destruction of man-made structures and the instigation of other natural disasters, such as tsunamis, avalanches and landslides.

In the next section, we'll examine the powerful forces that cause this intense trembling and find out why earthquakes occur much more often in certain regions.