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1. 1.Many natural events such as volcanic eruptions or meteor impacts can cause an earthquake, but the majority of naturally-occurring earthquakes are caused by movements of the earth's plates.
2. 2.20 constantly moving plates make up the surface of the earth. As the plates move they put force on themselves and each other, which, when large enough, causes the crust to break. When the break occurs, the stress is released as energy which moves through the Earth in the form of waves, which we feel and call an earthquake.
3. 3.According to the U.S. 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 quakes are extremely weak.
4. 4.Almost 80 percent of all the planet's earthquakes occur along the rim of the Pacific Ocean, called the "Ring of Fire," a region that encircles the Pacific Ocean and is home to 452 volcanoes, that’s over 75% of the world's active and dormant volcanoes.
5. 5.Each year the southern California area has about 10,000 earthquakes. Most of are so small that they are not felt. If there is a large earthquake, however, the aftershock sequence will produce many more earthquakes of all magnitudes for many months.
6. 6.The largest recorded earthquake in the United States was a magnitude 9.2 that struck Prince William Sound, Alaska on March 28, 1964.
7. 7.The largest recorded earthquake in the world was a magnitude 9.5 in Chile on May 22, 1960.
8. 8.When the Chilean earthquake occurred in 1960, seismographs recorded seismic waves that traveled all around the Earth. These seismic waves shook the entire earth for many days.
9. 9.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.
10. 10.An undersea earthquake in the Indian Ocean triggered a series of devastating tsunamis on December 26, 2004. The tsunamis struck along the coasts of most landmasses bordering the Indian Ocean, killing more than 225,000 people in eleven countries, and inundating coastal communities with waves up to 100 feet high.
11. 11.Alaska is the most earthquake-prone state and one of the most seismically active regions in the world, experiencing a magnitude 7.0 earthquake almost every year, and a magnitude 8.0 or greater earthquake on average every 14 years.