The magnitude 5.2 earthquake that rocked the Midwest on Friday was felt from Kansas to Georgia, and aftershocks could continue for months at this strange seismic zone at the nation's center and even trigger another big quake, a geophysicist said.
The quake occurred on a northern extension of the New Madrid fault, about 6 miles north of Mt. Carmel, Ill. The New Madrid fault was responsible for devastating quakes in the Mississippi Valley in 1811 and 1812. So the Friday quake and its aftershocks likely are raising the blood pressure of some residents and scientists.
For decades, scientists have debated whether and when the underlying fault could generate another temblor of similar and deadly strength.
"I think we saw a window to this possibility today in the Wabash Valley," said geophysicist Allessandro Forte of the Universite du Quebec à Montreal, who has studied the region's seismicity. "It's to the north of the New Madrid seismic zone, but given the strength of crust, the stress can be distributed great distances. It's not clear if we could see something in the next few years or even next few months, I would say."
The last earthquake in the region to approach the severity of Friday's temblor was a 5.0 magnitude quake that shook a nearby area in 2002, according to the U.S. Geological Survey.
An event actually surpassing today's magnitude last occurred in 1968, a magnitude 5.3 quake that was felt in 23 states, said Forte. The magnitude scale is logarithmic so a change of 0.1 or 0.2 makes a big difference in terms of energy output. The 1968 event was felt in Ontario and Boston.
"The $64,000 question is what this earthquake portends for the future," Forte said. "The answer is I'm afraid it can go either way."
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