Check Out These Interesting Earthquake Facts

Here are a few interesting earthquake facts shared through the Earthquake Hazards Program of the United States Geological Service (USGS):

1.  The largest recorded earthquake in the United States was a magnitude 9.2 that struck Prince William Sound, Alaska on Good Friday, March 28, 1964.

2.  The largest recorded earthquake in the world was a magnitude 9.5 in Chile on May 22, 1960.

3.  Alaska is the most earthquake-prone state and one of the most seismically active regions in the world.  Alaska experiences a magnitude 7 earthquake almost every year, and a magnitude 8 or greater earthquake on average every 14 years.

4.  From 1975 to 1995 there were only 4 states that did not have any earthquakes:  Florida, Iowa, North Dakota and Wisconsin.

5.  Florida and North Dakota have the smallest number of earthquakes in the United States.

6.  The magnitude of an earthquake is a measured value of the earthquake size.  The magnitude is the same no matter where you are, or how strong or weak the shaking was in various locations.  The intensity of an earthquake is a measure of the shaking created by the earthquake, and this value does vary with location.

7.  Most earthquakes occur at depths of less than 50 miles (80 km) from the Earth’s surface.

8.  The hypocenter of an earthquake is the location beneath the earth’s surface where the rupture of the fault begins.  The epicenter of an earthquake is the location directly above the hypocenter of the surface of the earth.

9.  A seiche (pronounced SAYSH) is what happens in a swimming pool during and after an earthquake.  It is “an internal wave oscillating in a body of water” or, in other words, it is the sloshing of the water in a swimming pool, or any body of water, caused by the ground shaking in an earthquake.  It may continue for a few moments or hours, long after the generating force is gone.  A seiche can also be caused by wind or tides.

10. The swimming pool at the University of Arizona in Tucson lost water from a seiche (sloshing) caused by the 1985 Magnitude 8.1 Michoacan, Mexico earthquake 1240 miles (2000 km) away.