Illinois & Indiana: 23 earthquakes in four days

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Illinois & Indiana: 23 earthquakes in four days

Post#1 » Thu Apr 24, 2008 4:33 pm ... aters-say/

23 earthquakes in four days have some Tri-Staters saying enough is enough
By Mark Wilson (Contact)
Tuesday, April 22, 2008

At least 23 earthquakes have shaken the Tri-State during the past four days, including the magnitude 5.2 shocker Friday and a 4.0 aftershock early Monday that was one of the strongest yet.

While all that shaking might be bad for Tri-State nerves, it could be good for science, some geologists say, and ultimately will help the area prepare for an even bigger earthquake in the future.

Geologists said the temblor just before 12:40 a.m. Monday registered magnitude 4.0 at its epicenter about five miles northwest of Mount Carmel, Ill.

Monday’s aftershock was in the same area as Friday’s quake, which itself was followed by a magnitude 4.6 aftershock 5½ hours later, along with a spate of smaller quakes throughout the weekend.

“It shook me awake, and I grabbed my 3-month-old and my wife and got under the table, just like we practice,” said Colby Rigg, mayor of Bellmont, Ill. Rigg, who is also Edwards County’s 911 coordinator and assistant emergency management agency coordinator, said he has had enough of all the shaking and rumbling.

“Just like anybody else, I’m concerned about it. It’s the noise that worries me. The noise is just unbelievable.

“It’s like a freight train coming through the house. I am tired of it.

“I’m ready to get a good night’s rest without having to worry about the earthquake alarm instead of the alarm clock.”

Monday morning’s shaking was considered an aftershock from Friday’s earthquake, although aftershocks are by definition earthquakes themselves, said Jessica Sigala, a geophysicist with the U.S. Geological Survey.

Aftershocks lessen

Typically, aftershocks after a larger quake gradually decrease in strength as the built-up energy within the earth exhausts itself. Events of greater magnitude, such as Monday morning’s, are rare, she said.

“It doesn’t happen very often, but it does happen,” she said. “Earthquakes are so unpredictable — they happen on their own.”

Sigala said researchers will use this aftershock as an opportunity to further study fault lines and seismic activity in the Midwest. Less is known about earthquakes here because they happen so infrequently compared with places such as California.

“We’re learning all the time when we have earthquakes like this,” she said.

The quake originated in the Wabash Valley Seismic Zone, a series of faults straddling the Wabash River in Illinois and Indiana.

Scientists know relatively little about them compared with fault systems in California or the New Madrid fault, which lies just south of the Tri-State along the Mississippi River Valley.

The Wabash Valley system has been more active in producing greater-magnitude quakes in the last 40 years compared with the New Madrid, Mike May, a professor of geology at Western Kentucky University, said.

Prehistoric big one

Although the New Madrid has produced catastrophic 7.0 or stronger quakes, such devastating quakes haven’t occurred in the Wabash Valley since prehistoric times.

As a result, many seismologists believe activity in the New Madrid zone is waning, May said.

But research has continued to be directed at the New Madrid instead of the Wabash Valley.

So while geologists might look at all this weekend’s seismic activity, or even that of the last few decades, as a brief blip in geologic time, all the tremors might serve a more immediate purpose, May said.

“All the activity since 1968 that people have felt, it is all due to the Wabash Valley.

“That is the significant thing. Research and funding for research in society is somewhat politically focused,” he said.

Not asleep

As a result, much more funding has been directed toward studying the New Madrid Seismic Zone, May said.

“I think this is a good thing, because we can say the Wabash Valley is not asleep. In that sense, it is a good thing this has happened, for science’s sake, if we can get some federal dollars.

“We know that this area is seismically active, and prehistorically we know there have been some monster earthquakes in this region.

“People would rest better at night if we knew more about this. Right now we just simply don’t know.”

Much of what is known about the Wabash Valley Seismic Zone comes from oil company data, said geologist Gary Patterson, information services director at the Center for Earthquake Research and Information.

The Memphis, Tenn., center also is the regional operational center for the Advanced National Seismic System.

The system’s task is to provide accurate and timely data of seismic events, including their effects on buildings and structures, to create a nationwide network of more than 7,000 earthquake sensor systems.

High-profile cracks

But while Congress is authorized to spend about $30 million a year on the network, it has received only between $1 million and $8 million a year since it began in 2000, Patterson said, and most of that money has been spent in the high-profile seismic areas of California.

“It’s not pork, it’s not earmarks. It is an existing project that has not been adequately funded,” he said.

More funding could be used to increase the number of monitoring stations throughout the region.

More monitoring stations will provide more information for scientists to study.

While that is unlikely to help predict earthquakes, it will help to better understand how earthquakes affect people, providing valuable information for improving building codes and safety procedures.

“It helps us inform the community about the hazards that a particular fault represents,” Patterson said.

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