Sunday, April 29, 2012

Is The Recent Increase In Felt Earthquakes In The Central U.S. Natural Or Manmade?

USGS scientists have been investigating the recent increase in the number of magnitude 3 and greater earthquakes in the midcontinent of the United States. Beginning in 2001, the average number of earthquakes occurring per year of magnitude 3 or greater increased significantly, culminating in a six-fold increase in 2011 over 20th century levels.

A map showing significant earthquakes in the midcontinental area analyzed for links between felt earthquakes and energy development. 
See caption:
Credit: USGS

An increase in earthquakes such as this prompts an important question: are they natural, or man-made? To address this question, a team of USGS scientists analyzed changes in the rate of earthquake occurrence in the midcontinent using large USGS databases of earthquakes recorded since 1970.

This graph shows the cumulative number of earthquakes M 3 or greater in the midcontinental United States. The number of M3 or greater earthquakes increases steadily at about 21 events per year until around 2000, when it increases about 50% to 31 events per year. By 2004, the number increased sharply to about 151 events per year. 
See caption:
Credit: USGS

Our scientists then took a closer look at earthquake rates in regions where energy production activities have changed in recent years. To learn more about their findings, please visit Deputy Secretary of the Department of the Interior David Hayes’ blog post here.

To learn more about the link between deepwell fluid injection, a method of the disposal of wastewaters from practices like hydraulic fracturing, and triggered earthquakes, please visit our FAQs.


Contacts and sources:
USGS

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