Tuesday, January 24, 2012

[Geology2] Geologists see faults in Illinois earthquake fears

Geologists see faults in Illinois earthquake fears

Monday, January 23, 2012

By Craig Sterrett

Geologists see faults in Illinois earthquake fears
Things were shaking all over the eastern United States on Feb. 7, 1812, although seismologists recently have downgraded the severity of the great temblor. The first of the series of four quakes at three fault lines in the New Madrid Seismic Zone was Dec. 16, 1811.

NT photo/Craig Sterrett

Midwesterners in nine states including Illinois may hear scary stories about the potential for a major earthquake as the 200th anniversary of the great New Madrid earthquake nears on Feb. 7.

But it shouldn't be all that big of a worry here in North Central Illinois. That was the basic message to about 30 people who attended a free program Sunday at Starved Rock State Park Visitors Center.

Noting the government is planning 10:30 a.m. earthquake-preparedness drills on Feb. 7, a 38-year geology instructor shared with the audience scientists' recent reports that the greatness of the New Madrid earthquake has been slightly exaggerated.

Ottawa High geology teacher and Illinois Valley Community College ecology instructor Joe Jakupcak said for years students in Illinois have been taught that the temblor was one of the biggest in history, that it shook so hard a church bell rang in Boston and that it caused the Mississippi to change course. There are no photos, there were few people living in that region (Memphis didn't yet exist and New Madrid was bigger than St. Louis at the time) and historians have to rely on written and artistic accounts.

Some of the popular history of the 1812 earthquake are true and some legend. To be accurate, the quake was the biggest in recorded Midwest history — and the severity of the quake always has been an estimate. Instead of it causing a bell to ring in a church tower in Boston, it caused a bell to ring in Charleston, S.C. — hundreds of miles nearer than Boston to the epicenter of the Feb. 7, 1812.

To be sure, it was a violent earthquake for the few thousand who lived near the center of the quake.

"Trees were falling in every direction — some torn up by the roots, others were breaking off above the ground and limbs were flying everywhere," Jakupcak said, reading from one written account. Jakupcak said naturalist John James Audubon was in the region at the time and wrote that his horse had become panicked when the ground started to shake and he stood with his horse until it subsided.
Another account indicated, "The earth was horribly torn to pieces."

He said indeed there would have been "sand blow," where the movement of the earth would cause liquefaction of sand and cause it to rise to the surface and in the meantime swallow up what might have been on the surface. Jakupcak said sand blow is why, after the violent recent earthquakes in New Zealand, there were photos of vehicles strangely sucked halfway into the ground.

Some of the trees that survived the 1812 quake were bent and misshapen. Jakupcak showed a 1904 photo of how some of the trees had straightened and resumed growing upward. The flooding and creation of Reelsfoot Lake killed out all the woodland hardwoods but water-loving tupelo trees survived. (But in the coldest winters, settlers would go out onto the iced-over lake to gradually cut tupelo trees for firewood.)

The historic earthquake was south of Cairo, Ill., near a sharp S-shaped bend in the river near New Madrid, Mo., at the top of Missouri's boot heel.
One thing the earthquake definitely did do was cause a portion of the Mississippi River to reverse course for several hours. Men who shipped freight downstream on rafts witnessed it. "Boatmen, if they said the river is going backwards, we don't have any reason to question it," Jakupcak said.
Part of the fault line that moved on Feb. 7, 1812, rose up 10 feet. That fault line crosses the river in three spots, and where it rose up in the farthest upstream part of the river, it created a dam that temporarily diverted the river southeast into low woodlands, forming the 12,000-acre Reelsfoot Lake.
Eventually, the force of the river current knocked down the natural low-head dam because the river bottom is mud, and the reverse churning effect from the fault ceased.

Judging from accounts and art and the fact that it could have been felt throughout nine states including all of Illinois, the estimate for years was that the earthquake would have measured 8.0 on the Richter scale. One of the best indicators of the damage showed how the earthquake caused log cabins to tilt. Now scientists believe it was "nowhere near an 8," and one recent estimate by Susan Hough, U.S. Geological Survey seismologist, was that it was more like a 7.0.

Geologists and seismologists keep close watch on the three faults near New Madrid and have determined that the faults have barely been moving and when they have, there has been little "strain" at that location, Jakupcak said. In 1999, for example, no motion was found at all at 30 different locations, he said.

In particular, Jakupcak and some seismologists are at odds the common cry that the New Madrid Seismic Zone tends to produce a big earthquake every 200 years.

He said Northwestern University seismology professor Seth Stein "says there's nothing going on" at New Madrid and "sees no reason for alarm."
Before taking questions from the audience, Jakupcak wrapped up his presentation with Stein's observation: "Apocalyptic predictions have very low track records."

Longtime L-P history teacher Bill Johnson spoke up about how a climatologist in the 1990s predicted a major earthquake based on the alignment of various things above the earth and in the heavens, and as a result, the insurance industry made out well by selling Illinois residents, even northern Illinois residents, earthquake insurance.

"If I remember, that prediction turned out to be a boon for the insurance industry," Johnson said.

PRESS RELEASE: IEMA encourages participation
in multi-state earthquake drill ...

SPRINGFIELD — At 10:15 a.m. Feb. 7, 2012, millions of people in the Central United States will seek shelter under their desks, kitchen tables and other sturdy objects as part of the second annual "Great Central U.S. ShakeOut" earthquake drill.

Illinois Emergency Management Agency is encouraging people to register for the multi-state drill.

"The drill takes just a few minutes, but the lessons learned can save countless lives," said IEMA Director Jonathon Monken. "Many people don't realize that the most powerful earthquakes to ever occur in the U.S. took place 200 years ago along the New Madrid Seismic Zone, which reaches into southern Illinois. That risk, along with the Wabash Valley Seismic Zone in southeastern Illinois and numerous other faults throughout the state, is why we're encouraging residents to take part in the ShakeOut drill."

Monken said schools, businesses, government agencies, families and others are encouraged to register to participate in the drill at www.shakeout.org/centralus. Registered participants will receive additional information about the drill and earthquake preparedness.
More than three million people in 11 states participated in the first "Great Central U.S. ShakeOut" on April 28, 2011, including nearly 260,000 participants in Illinois. The drill focuses on the "Drop, Cover and Hold On" protective actions people should take when an earthquake begins: "Drop" down to the floor, take "Cover" under a sturdy desk, table or other furniture, and "Hold On" to the furniture item and be prepared to move with it until the shaking stops.

The date for the 2012 ShakeOut drill coincides with the 200th anniversary of the Feb. 7, 1812, earthquake near New Madrid, Mo., the last of a series of earthquakes that were felt as far away as the east coast. The event is being organized by the Central United States Earthquake Consortium and its member states of Alabama, Arkansas, Kentucky, Illinois, Indiana, Mississippi, Missouri and Tennessee.
More information is at www.Ready.Illinois.gov.


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