Purdue earthquake expert says April 18 earthquake largest recorded for the Wabash Vally fault system
WEST LAFAYETTE, Ind. - A Purdue University researcher says earthquake activity in the Midwest has been moderate in recent years, but the area has a history of much more powerful quakes. Larry Braile, head of the Department of Earth and Atmospheric Sciences, said the Midwest region includes both the Wabash Valley fault system that was hit Friday (April 18) and the New Madrid seismic zone.
(Media-Newswire.com) - WEST LAFAYETTE, Ind. - A Purdue University researcher says earthquake activity in the Midwest has been moderate in recent years, but the area has a history of much more powerful quakes. Larry Braile, head of the Department of Earth and Atmospheric Sciences, said the Midwest region includes both the Wabash Valley fault system that was hit Friday ( April 18 ) and the New Madrid seismic zone.
He said the magnitude 5.2 earthquake early Friday ( April 18 ) was one of the more powerful earthquakes in recent years.
"The most powerful quake in the Midwest within the past 50 years was the magnitude 5.5 in 1968," Braile said. "This earthquake is the most powerful on record for the Wabash Valley zone."
The Wabash Valley zone has produced earthquakes of 4.6 magnitude in 1974, approximately 5 magnitude in 1987 and 4.6 magnitude in 2002.
Braile said unlike the Wabash Valley zone, the New Madrid fault has had powerful earthquakes capable of causing severe damage.
"The New Madrid seismic zone was the location of a series of three 7.0 to 7.5 earthquakes in 1811-1812," Braile said. "The Midwest area is capable of producing powerful earthquakes, however, the average recurrence of a 7-plus magnitude earthquake for the New Madrid zone is approximately 1,000 years, so the probability in any given year is very small."
Studies of past earthquakes and statistical evaluations suggest that the Wabash Valley zone is expected to have a magnitude 4 earthquake about every two years and a magnitude 5 about every 10-20 years.
Every whole-number increase in magnitude on the earthquake scale indicates that the quake produces about 10 times greater shaking, Braile said.
"People can feel about a 2.5 magnitude quake, and a magnitude 5 quake can cause minor damage," he said. "Typically an earthquake must be of magnitude 6 or greater to cause significant damage."
Purdue scientists, including those in the Geodynamics and Active Tectonics Group, are studying the mechanisms that create earthquakes and ways to better determine the probability of future quakes.
Writer: Elizabeth Gardner, ( 765 ) 494-2081, ekgardner@purdue.edu
Source: Larry Braile ( 765 ) 494-5979, braile@purdue.edu
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