Post by Keith Yearman on Feb 11, 2010 3:29:14 GMT -5
www.chicagotribune.com/news/local/northnorthwest/chi-100210-earthquake-explainer-story,0,5661695.story
chicagotribune.com
Earthquake's origins remain a mystery
By John Keilman and Ted Gregory
Tribune staff reporters
8:20 PM CST, February 10, 2010
Philip Carpenter happened to be awake when Wednesday's earthquake shook his Sycamore home, and unlike many people who nervously rode out the tremors, he found the moment exhilarating.
Carpenter is a Northern Illinois University geology professor who studies earthquakes and other geological activity for a living. But until those few shaky seconds, he had never felt one on his home turf.
"To my knowledge, there have been no recorded earthquakes in that area," he said.
The quake's center, near the Kane County town of Hampshire, was far from any known fault line, and its origin remains a tantalizing mystery. But a research project set to begin in the area might provide answers on just what's going on deep beneath the surface of northern Illinois.
The federally funded project, known as EarthScope, will plant 400 seismometers across the Midwest to measure seismic activity. The information collected by the instruments will help scientists create images of hidden fault lines and other subterranean "scar tissue" left over from millennia of underground activity.
Those images, in turn, could help to explain why the earth moved, albeit gently, in northern Illinois, an area that rarely experiences earthquakes.
"Maybe then we can see these ancient scars in the crust and finally put it all together," said Tim Larson, a geophysicist with the Illinois State Geological Survey. Wednesday's earthquake was only the fourth in northern Illinois since 1985, according to the U.S. Geological Survey. All have been mild: The latest, which caused no recorded damage, measured 3.8 in magnitude; the 7.0 quake that devastated Haiti last month was about 32,000 times more powerful.
Still, it was a hot topic at the General Store of Udina, a faux log cabin structure about two miles east of the epicenter.
"OMG!" proprietor Cindy Kamijima wrote on the store's whiteboard. "Did anyone else feel the Earthquake?"
It was the first question she and colleague Charlene LaCasse asked of anyone who walked in the establishment. Kamijima was getting ready to open the store when she felt the jolt at 3:59 a.m. She thought it was a snowplow, then looked outside and saw nothing.
Regular customer Bill Miller had a more sinister first impression. He thought military planes were flying toward Chicago after a terrorist attack. "I thought it was a sonic boom, to tell the truth, because they scramble jets through here out of Milwaukee and Rockford," he said.
Managers at VIP Property Maintenance, a landscaping, snow removal and valet service about a mile east of the epicenter, started getting phone calls moments after the tremor, said Kellie Florence, administrative assistant at the company.
"They thought our snow plows were hitting their buildings," Florence said. "Our regional manager was in a truck and had no idea. He just said, 'OK, we'll get right on it.''' More than 17,000 people told the U.S. Geological Survey they felt the quake. Those who felt it most strongly lived in Fox River towns from Algonquin to Oswego, but Wisconsin and Indiana residents also experienced the tremors.
Scientists could offer no clear answers about the cause. The closest known fault line runs beneath the small town of Sandwich, Ill., about 40 miles south of the epicenter, but it has been dormant for at least 150 years, experts said.
The quake was small enough that geologists did not expect any aftershocks, which would have offered an opportunity for follow-up seismic measurements. And it took place far underground, anywhere from 3 to 6 miles beneath the surface, where most geological features are still unmapped. But the EarthScope project, with its battery of seismometers, could provide insight on that hidden territory.
Anne Trehu, EarthScope's current director, said the instruments are placed in a grid pattern, with one every 43 miles, to continually record seismic waves. Those data are used to create models of what's taking place underground, including the stresses that could be building up inside the plate upon which Chicago rests. The research probably won't yield life-or-death information for Illinois residents: Experts said that Illinois, sitting on the middle of the North American plate, is much less likely to experience a powerful earthquake than California on the plate's western edge.
But Larson said it might shed light on one theory: that the state's earthquakes could be the result of glaciers that receded north about 15,000 years ago. Relieved of the weight of the ice, the crust could still be slowly bouncing back into place, causing underground disturbances.
Carpenter, who hopes to use some of EarthScope's data in his own research, said the information could have a more practical payoff, too. He hopes to use it to monitor the condition of northern Illinois' aquifers, the underground source of drinking water for many residents.
"It does have some applications to environmental problems," he said.
The seismometers, which are gradually being deployed across the country, should arrive within the next two years.
jkeilman@tribune.com tgregory@tribune.com
Copyright © 2010, Chicago Tribune
chicagotribune.com
Earthquake's origins remain a mystery
By John Keilman and Ted Gregory
Tribune staff reporters
8:20 PM CST, February 10, 2010
Philip Carpenter happened to be awake when Wednesday's earthquake shook his Sycamore home, and unlike many people who nervously rode out the tremors, he found the moment exhilarating.
Carpenter is a Northern Illinois University geology professor who studies earthquakes and other geological activity for a living. But until those few shaky seconds, he had never felt one on his home turf.
"To my knowledge, there have been no recorded earthquakes in that area," he said.
The quake's center, near the Kane County town of Hampshire, was far from any known fault line, and its origin remains a tantalizing mystery. But a research project set to begin in the area might provide answers on just what's going on deep beneath the surface of northern Illinois.
The federally funded project, known as EarthScope, will plant 400 seismometers across the Midwest to measure seismic activity. The information collected by the instruments will help scientists create images of hidden fault lines and other subterranean "scar tissue" left over from millennia of underground activity.
Those images, in turn, could help to explain why the earth moved, albeit gently, in northern Illinois, an area that rarely experiences earthquakes.
"Maybe then we can see these ancient scars in the crust and finally put it all together," said Tim Larson, a geophysicist with the Illinois State Geological Survey. Wednesday's earthquake was only the fourth in northern Illinois since 1985, according to the U.S. Geological Survey. All have been mild: The latest, which caused no recorded damage, measured 3.8 in magnitude; the 7.0 quake that devastated Haiti last month was about 32,000 times more powerful.
Still, it was a hot topic at the General Store of Udina, a faux log cabin structure about two miles east of the epicenter.
"OMG!" proprietor Cindy Kamijima wrote on the store's whiteboard. "Did anyone else feel the Earthquake?"
It was the first question she and colleague Charlene LaCasse asked of anyone who walked in the establishment. Kamijima was getting ready to open the store when she felt the jolt at 3:59 a.m. She thought it was a snowplow, then looked outside and saw nothing.
Regular customer Bill Miller had a more sinister first impression. He thought military planes were flying toward Chicago after a terrorist attack. "I thought it was a sonic boom, to tell the truth, because they scramble jets through here out of Milwaukee and Rockford," he said.
Managers at VIP Property Maintenance, a landscaping, snow removal and valet service about a mile east of the epicenter, started getting phone calls moments after the tremor, said Kellie Florence, administrative assistant at the company.
"They thought our snow plows were hitting their buildings," Florence said. "Our regional manager was in a truck and had no idea. He just said, 'OK, we'll get right on it.''' More than 17,000 people told the U.S. Geological Survey they felt the quake. Those who felt it most strongly lived in Fox River towns from Algonquin to Oswego, but Wisconsin and Indiana residents also experienced the tremors.
Scientists could offer no clear answers about the cause. The closest known fault line runs beneath the small town of Sandwich, Ill., about 40 miles south of the epicenter, but it has been dormant for at least 150 years, experts said.
The quake was small enough that geologists did not expect any aftershocks, which would have offered an opportunity for follow-up seismic measurements. And it took place far underground, anywhere from 3 to 6 miles beneath the surface, where most geological features are still unmapped. But the EarthScope project, with its battery of seismometers, could provide insight on that hidden territory.
Anne Trehu, EarthScope's current director, said the instruments are placed in a grid pattern, with one every 43 miles, to continually record seismic waves. Those data are used to create models of what's taking place underground, including the stresses that could be building up inside the plate upon which Chicago rests. The research probably won't yield life-or-death information for Illinois residents: Experts said that Illinois, sitting on the middle of the North American plate, is much less likely to experience a powerful earthquake than California on the plate's western edge.
But Larson said it might shed light on one theory: that the state's earthquakes could be the result of glaciers that receded north about 15,000 years ago. Relieved of the weight of the ice, the crust could still be slowly bouncing back into place, causing underground disturbances.
Carpenter, who hopes to use some of EarthScope's data in his own research, said the information could have a more practical payoff, too. He hopes to use it to monitor the condition of northern Illinois' aquifers, the underground source of drinking water for many residents.
"It does have some applications to environmental problems," he said.
The seismometers, which are gradually being deployed across the country, should arrive within the next two years.
jkeilman@tribune.com tgregory@tribune.com
Copyright © 2010, Chicago Tribune