Southern California was rocked by a second major earthquake Friday night, as a 7.1 magnitude struck at around 8:30.
The ground moving beneath our feet can be scary, but a little knowledge can go a long way.
Here are some fast facts about earthquakes you might like to know:
- Smaller aftershock earthquakes often follow the main shock.
- An earthquake is caused by the breaking and shifting of rock beneath the earth's surface.
- Ground shaking from earthquakes can collapse buildings and bridges; disrupt gas, electric and phone service and, sometimes, trigger landslides, avalanches, flash floods, fires and huge, destructive ocean waves (tsunamis).
- Most earthquake-related injuries result from collapsing walls, flying glass and falling objects.
- Several thousand shocks of varying sizes occur annually in the United States and 70 to 75 damaging earthquakes occur throughout the world each year.
- All 50 states and all U.S. territories are vulnerable to earthquakes. Where earthquakes have occurred in the past, they will happen again.
- California experiences the most frequent damaging earthquakes; however, Alaska experiences the greatest number of large earthquakes—most located in uninhabited areas.
- Earthquakes occur most frequently west of the Rocky Mountains, although historically, the most violent earthquakes have occurred in the central United States.
- The largest earthquakes felt in the United States were along the New Madrid Fault in Missouri, where a 3-month-long series of quakes from 1811 to 1812 included three quakes larger than a magnitude of 8 on the Richter Scale. These earthquakes were felt over the entire eastern United States (over 2 million square miles), with Missouri, Tennessee, Kentucky, Indiana, Illinois, Ohio, Alabama, Arkansas and Mississippi experiencing the strongest ground shaking.
- The Richter Scale, developed by Charles F. Richter in 1935, is a logarithmic measurement of the amount of energy released by an earthquake. Earthquakes with a magnitude of at least 4.5 are strong enough to be recorded by sensitive seismographs all over the world.