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Monday, Apr. 20, 2015

Geologist says area not prepared for major quake

Thursday, August 19, 2004

Staff Writer

Imagine waking up at 3 a.m. in the morning to an event that sounds like a bomb going off. Your house is shaking furiously. Books, dishes and other loose objects fly out of cupboards and shelves. Outside of your house, the earth opens up, forming a huge crevice that swallows your car.

Suddenly the shaking stops. Quickly you turn on the television to see what is happening.

On the television screen you see people scrambling as the St. Louis Arch topples into the Mississippi River. Newscasters tell you that the Mississippi River's course has been violently altered and is now running through downtown Memphis. A quick satellite feed to Memphis shows the Mississippi River pushing the Pyramid off its foundation.

The Mississippi River Valley has just been rocked by a massive earthquake.

The story above sounds like a Hollywood disaster movie. Perhaps the damage caused by a major quake wouldn't be as severe as the scene described above, but according to Gary Patterson, a geologist at the University of Memphis, it's not a matter of if a major earthquake will hit this region, it's a matter of when.

Patterson spoke about the chances of a major quake along the New Madrid fault line Aug. 5 at the Spring River Gem and Mineral Club's meeting at Omaha Center.

The New Madrid fault line (or seismic zone) covers northern Arkansas, eastern Tennessee, most of Missouri and parts of Kentucky and Illinois.

"There is a nine in 10 chance that a magnitude six to seven earthquake will hit the New Madrid seismic zone in the next 50 years," Patterson said.

Patterson said geologists and seismologists have come to this conclusion based on the history of the New Madrid seismic zone and current geological activity taking place in the Mississippi River Valley area.

Recently, geologists working near the New Madrid Fault line uncovered a series of deposits known as liquid faction deposits. He said liquid faction deposits are formed from vigorously shaken sediments that liquefy after a violent earthquake.

Patterson said the liquid faction deposits in the Mississippi River Valley region are the largest in the world. He said artifacts found inside these deposits show how this area has been hit with tremendous earthquakes in the past.

The most recent major New Madrid fault line earthquakes and the largest in U.S. history occurred in the early 1800s near Commerce, Mo. Three 8.0 earthquakes devastated the region in the fall of 1811, according to geologists. The quakes were so powerful they changed the course of the Mississippi River (creating Reelfoot Lake in northern Tennessee) and rang church bells in Boston, said Patterson.

Patterson said the 1811 quakes in the New Madrid seismic zone were the latest in a series of powerful quakes that have hit the region. He said archeological evidence uncovered inside liquid faction deposits showed the region was hit with major earthquakes in the late 900s and the 1400s.

Patterson said while major earthquakes occur once or twice every few centuries, the New Madrid seismic zone produces many smaller quakes. He said east of the Rockies, the Mississippi River Valley is the most seismically active area of the United States.

Patterson said the effects of a major earthquake in this region would be devastating. He said the overwhelming majority of buildings are not built to withstand the forces associated with a powerful quake.

"Not only are the buildings inadequate, but the emergency response teams are ill-prepared for a disaster of this type," he said.

Patterson estimates there would be over 15,000 casualties in Memphis if a quake hit during the day. He said if a large earthquake occurred at night the casualty rate would be approximately 1,700. He said the number of casualties would be higher in the daytime because people would be concentrated in the downtown area where many old buildings are located.

Patterson, who is currently working on his Ph.D in earth sciences at the University of Memphis, said he and other members of the U.S. Geological survey team travel to earthquake stricken areas all over the world to collect data to help engineers and emergency response teams in the event of an earthquake.

He and a team of geologists went to Taiwan in 1999 after a 7.6 earthquake hit the island and to India in 2001 after 7.0 earthquake devastated rural towns and cities.

The India earthquake was of particular interest because it occurred on a fault line similar to the New Madrid's.

Patterson said the work he and his team did in India was serious but humor crept into the picture at least once. He and his colleagues set up some equipment in the desert on the India/Pakistan border next to a large liquid faction deposit. They offered to pay an old man to watch their equipment so it wouldn't get stolen. The old man said he would watch it for free.

"Three weeks later we came back and the old man had a tent set up near our equipment. Pictures of the area were being broadcast over the Internet and the old man was charging scientists a fee to see the area. With a gun in his hand he escorted scientists to the sight one at a time. He also sold them tea," Patterson said, laughing.

All humor aside, Patterson said the information gleaned from earthquake sites helps local and state governments develop building codes that minimize earthquake damage.

Recommendations include building foundations out of solid concrete, with few open areas on the first floor, and building lighter roofs.

"Arkansas has great building codes. In 2001 the state adopted the international building code which assigns blame to construction companies if a structure isn't built to code and it fails during a catastrophe," he said.

Predicting what how a major earthquake would effect northcentral Arkansas would be tricky, Patterson said. He said a quake could cause severe property damage and change the flow of rivers like the Spring and South Fork.

He said the water table would be affected and the Mammoth Spring would probably cease to exist as we know it.

"We have strong evidence that an earthquake in Alaska affected water tables in Kansas. Who knows what would happen here?" he said.

Patterson said he admits there are numerous problems people face in their everyday lives that affect them, and earthquakes probably are not on that list. He said he doesn't want to alarm the public, just increase their awareness and preparedness in the event of a disaster.

"A major earthquake -- it will happen. We just don't know when," he said.



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