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A new earthquake threat interesting read
ints of quake under central USA
By Patrick O'Driscoll, USA TODAY
The sleeping giant of American earthquake faults, the New Madrid zone in the middle of the country, may be showing new signs of activity.
University of Colorado Geological Sciences Professor Karl Mueller works with a backhoe operator on trenching part of the New Madrid Seismic Zone.
By University of Colorado via AP
The journal Nature reported in June that a University of Memphis study had detected a half-inch of fault shift in the past five years. The movement, detected with the Global Positioning System (GPS), could be a sign that pressure is building toward a significant quake in a region that's home to millions.
"We go from nothing moving to a little movement. That's a huge difference," says Arch Johnston, director of the university's Center for Earthquake Research and Information.
The New Madrid (pronounced MAD-rid) zone is the most seismically active region east of the Rocky Mountains. It is a 120-mile series of rifts deep beneath the Earth's surface along the Mississippi River.
Almost two centuries ago, it produced the largest earthquake ever in the continental USA. The earthquake, later estimated at magnitude 8.1 or stronger, was more powerful than any in California, home of the San Andreas fault.
But the New Madrid fault, named for a frontier Missouri village rocked by powerful quakes in the winter of 1811-12, hasn't had a big one since. The last of considerable strength, about magnitude 6.0, was in 1895. More than 100 quakes a year occur in the zone, which runs from northeastern Arkansas to southern Illinois. Most are too small to be felt.
"The hazard here is greater than one would think," says Eugene Schweig of the U.S. Geological Survey (USGS) office in Memphis. "Even if earthquakes happen somewhat less frequently here, they can cause damage over a much bigger area."
That's because seismic waves travel farther in the "very old, very cold and hard" crust under the central USA, Schweig says. Compared with the 1906 earthquake that all but destroyed San Francisco, the New Madrid quakes had "strong shaking over about 20 times as much area," he says.
The USGS calculates a 40% chance of a major earthquake of magnitude 6.0 or greater within the next 35 years, and a 10% chance of a quake the size of the ones that made New Madrid famous. "A repeat today of the earthquakes of 1811-12 would cause widespread loss of life and billions of dollars in property damage," a USGS fact sheet says.
Another group of researchers, however, questions the findings. A team from Northwestern University studied the New Madrid zone in 1998, also with GPS, but found no seismic movement. Team members, including Andrew Newman, now a professor at Georgia Tech, suggest that "noise" in the data and too few measuring points showing movement make the new results dubious.
"An 1811-type event is not very likely in our future," Newman says. "There's definitely fewer earthquakes there now." The last sizable one was in 1895, and "since then, none. In the same time, you've seen a couple of dozen on the San Andreas fault in California."
New Madrid's dynamics are largely unknown. In California, faults are easily studied because they are on the Earth's surface, where two continental plates collide. New Madrid's faults lie beneath thick sediments deposited over millions of years. Recent research also suggests the thick sediments may magnify, not dampen, the shockwaves of an earthquake.
Scientists believe the faults are a failed "rift" zone, created when Earth's crust was separating into continents. The crust fractured but did not split apart. That left a weak spot where earthquakes occur.
History shows that the New Madrid earthquakes were fearsome. In 1811 and 1812, three major quakes triggered landslides, caused the Mississippi River to flow backward, swamped boats, created a lake, leveled New Madrid, Mo., and knocked down chimneys and cabins in St. Louis and Cincinnati. The shaking caused church bells to ring in Boston.
In 1990, a New Mexico climatologist with no formal earthquake training predicted a big one for early that December. The forecaster supposedly had predicted the California's 1989 Loma Prieta earthquake. That quake, which struck as the World Series was being played in the San Francisco Bay Area, killed 63 people and caused $6 billion in damage.
No movement occurred in New Madrid except for an invasion of tourist traffic and news media. Sales of "It's our fault" T-shirts and "Quake burgers" were brisk.
The publicity did remind people that big earthquakes had happened there and could again. "Everybody got their earthquake kits together," says Schweig of the USGS. As fears subsided over the years, precautions were forgotten.
"We're somewhat overdue for a magnitude 6, but earthquakes are not 'on the clock,' " says Chuck Langston of the University of Memphis quake center. A variety of preparedness efforts already are underway:
• The Federal Emergency Management Agency is starting a "catastrophic planning initiative" for the Memphis area, the closest major city to the fault line. FEMA spokesman Butch Kinerney says the object is to prepare for any threat, not just an earthquake. But the project will be designed for a widespread disaster that perhaps only a quake could produce: schools, hospitals, airports and power plants hit at once.
• The USGS is mapping the geology in cities affected by the fault to identify areas most prone to quake damage. The mapping is finished for Memphis and has begun for St. Louis and Evansville, Ind.
• A major earthquake on the Mississippi River will be the scenario next June for the Coast Guard's annual "Spill of National Significance" exercise, a drill for accidents with oil or hazardous materials.
• A year-old, $235 million FEMA program that issues grants for designing and refurbishing buildings to withstand catastrophes is getting proposals that include earthquake readiness. Kinerney says at least two schools in the New Madrid region have added a "seismic component" to their grant requests.
• The USGS and other agencies conduct "Earthquake 101" seminars in cities within the zone. In June, a small quake occurred during one such meeting in Dyersburg, Tenn.
ints of quake under central USA
By Patrick O'Driscoll, USA TODAY
The sleeping giant of American earthquake faults, the New Madrid zone in the middle of the country, may be showing new signs of activity.
University of Colorado Geological Sciences Professor Karl Mueller works with a backhoe operator on trenching part of the New Madrid Seismic Zone.
By University of Colorado via AP
The journal Nature reported in June that a University of Memphis study had detected a half-inch of fault shift in the past five years. The movement, detected with the Global Positioning System (GPS), could be a sign that pressure is building toward a significant quake in a region that's home to millions.
"We go from nothing moving to a little movement. That's a huge difference," says Arch Johnston, director of the university's Center for Earthquake Research and Information.
The New Madrid (pronounced MAD-rid) zone is the most seismically active region east of the Rocky Mountains. It is a 120-mile series of rifts deep beneath the Earth's surface along the Mississippi River.
Almost two centuries ago, it produced the largest earthquake ever in the continental USA. The earthquake, later estimated at magnitude 8.1 or stronger, was more powerful than any in California, home of the San Andreas fault.
But the New Madrid fault, named for a frontier Missouri village rocked by powerful quakes in the winter of 1811-12, hasn't had a big one since. The last of considerable strength, about magnitude 6.0, was in 1895. More than 100 quakes a year occur in the zone, which runs from northeastern Arkansas to southern Illinois. Most are too small to be felt.
"The hazard here is greater than one would think," says Eugene Schweig of the U.S. Geological Survey (USGS) office in Memphis. "Even if earthquakes happen somewhat less frequently here, they can cause damage over a much bigger area."
That's because seismic waves travel farther in the "very old, very cold and hard" crust under the central USA, Schweig says. Compared with the 1906 earthquake that all but destroyed San Francisco, the New Madrid quakes had "strong shaking over about 20 times as much area," he says.
The USGS calculates a 40% chance of a major earthquake of magnitude 6.0 or greater within the next 35 years, and a 10% chance of a quake the size of the ones that made New Madrid famous. "A repeat today of the earthquakes of 1811-12 would cause widespread loss of life and billions of dollars in property damage," a USGS fact sheet says.
Another group of researchers, however, questions the findings. A team from Northwestern University studied the New Madrid zone in 1998, also with GPS, but found no seismic movement. Team members, including Andrew Newman, now a professor at Georgia Tech, suggest that "noise" in the data and too few measuring points showing movement make the new results dubious.
"An 1811-type event is not very likely in our future," Newman says. "There's definitely fewer earthquakes there now." The last sizable one was in 1895, and "since then, none. In the same time, you've seen a couple of dozen on the San Andreas fault in California."
New Madrid's dynamics are largely unknown. In California, faults are easily studied because they are on the Earth's surface, where two continental plates collide. New Madrid's faults lie beneath thick sediments deposited over millions of years. Recent research also suggests the thick sediments may magnify, not dampen, the shockwaves of an earthquake.
Scientists believe the faults are a failed "rift" zone, created when Earth's crust was separating into continents. The crust fractured but did not split apart. That left a weak spot where earthquakes occur.
History shows that the New Madrid earthquakes were fearsome. In 1811 and 1812, three major quakes triggered landslides, caused the Mississippi River to flow backward, swamped boats, created a lake, leveled New Madrid, Mo., and knocked down chimneys and cabins in St. Louis and Cincinnati. The shaking caused church bells to ring in Boston.
In 1990, a New Mexico climatologist with no formal earthquake training predicted a big one for early that December. The forecaster supposedly had predicted the California's 1989 Loma Prieta earthquake. That quake, which struck as the World Series was being played in the San Francisco Bay Area, killed 63 people and caused $6 billion in damage.
No movement occurred in New Madrid except for an invasion of tourist traffic and news media. Sales of "It's our fault" T-shirts and "Quake burgers" were brisk.
The publicity did remind people that big earthquakes had happened there and could again. "Everybody got their earthquake kits together," says Schweig of the USGS. As fears subsided over the years, precautions were forgotten.
"We're somewhat overdue for a magnitude 6, but earthquakes are not 'on the clock,' " says Chuck Langston of the University of Memphis quake center. A variety of preparedness efforts already are underway:
• The Federal Emergency Management Agency is starting a "catastrophic planning initiative" for the Memphis area, the closest major city to the fault line. FEMA spokesman Butch Kinerney says the object is to prepare for any threat, not just an earthquake. But the project will be designed for a widespread disaster that perhaps only a quake could produce: schools, hospitals, airports and power plants hit at once.
• The USGS is mapping the geology in cities affected by the fault to identify areas most prone to quake damage. The mapping is finished for Memphis and has begun for St. Louis and Evansville, Ind.
• A major earthquake on the Mississippi River will be the scenario next June for the Coast Guard's annual "Spill of National Significance" exercise, a drill for accidents with oil or hazardous materials.
• A year-old, $235 million FEMA program that issues grants for designing and refurbishing buildings to withstand catastrophes is getting proposals that include earthquake readiness. Kinerney says at least two schools in the New Madrid region have added a "seismic component" to their grant requests.
• The USGS and other agencies conduct "Earthquake 101" seminars in cities within the zone. In June, a small quake occurred during one such meeting in Dyersburg, Tenn.