Re: How long can an Earthquake last?

Dear Cody,

Earthquakes can last anywhere from one second to three or more minutes. The 1964 Alaska earthquake was one of the strongest earthquakes ever recorded at 9.2 magnitude on the richter scale. It lasted for 3 minutes!

For minor earthquakes, ground shaking usually lasts only a few seconds. Strong shaking from a major earthquake usually lasts less than one minute. For example, shaking in the 1989 magnitude 7.1 Loma Prieta (San Francisco) earthquake lasted 15 seconds; for the 1906 magnitude 8.3 San Francisco earthquake it lasted about 40 seconds.

As for the term "ground zero" that you refer to, that term is not an official term used by seismologists. Ground zero has a military origin and refers to the point on the ground directly under a nuclear bomb explosion. This term is now in wide use in everyday speech to describe the center of many actions and activities. Seismologists call the actual place where an earthquake occurs the "focus" or "hypocenter". This is where the rocks are actually breaking or rubbing together to create the earthquake. Earthquakes occur below the surface of the earth. Some are more than 700 kilometers (435 miles) below the surface but most occur within 70 kilometers (43.5 miles) within the surface. The term "epicenter" is the point on the Earth's surface directly above the focus.

I obtained this information from the U.S. Geological Survey's web site on earthquakes which you can find at: http://easternweb.er.usgs.gov/eastern/earthquakes/eqfaq.html

Good luck to you and thanks for the question