Pathfinder
Editor, Senior Moderator
Scientists debate area earthquake hazard
March 07, 2010 4:40 PM
By KATHIE BASSETT
<!-- Video goes here -->
In the aftermath of cataclysmic earthquakes in Haiti and Chile, residents are expressing renewed concern over the likelihood of an event occurring here.
Douglas Weins, chairman of the Department of Earth and Planetary Science at Washington University in St. Louis, cautioned against making broad assumptions regarding the potential for significant earthquake activity here based on recent events around the world, including the 3.7 magnitude earthquake that occurred last Tuesday in the New Madrid Seismic Zone in southeastern Missouri.
Weins emphasized that each of these earthquakes has occurred in different settings and need to be viewed as separate events, not part of a global pattern.
"It's extremely unfortunate that the two big earthquakes this year happened in densely populated areas," he said.
"In Chile, the earthquake occurred because the sea floor is slipping underneath the continent, so there is a rubbing," he said. "This is an inter-plate earthquake that was also connected to volcanic activity."
The situation in Haiti more closely resembles the setting in Chile than the one here in the Midwest, he explained further.
The New Madrid fault is located in the middle of the tectonic plate, not on plate boundaries like Chile and Haiti. The fault produces intra-plate earthquakes.
"It's really a crack in the plate, not part of a big seismic system like Chile," he said. "Haiti's earthquake was the result of different plates sliding past one another; the country is situated on a plate boundary."
In Haiti's case, Weins said it would be hard to think of a worse location for an earthquake to occur - under the capital city of one of the most impoverished nations in the Western Hemisphere. Even though the Chile earthquake was 100 times larger at magnitude 8.8 versus the magnitude 7.0 in Haiti, the damage was less severe, thanks to stricter building codes.
Wein's colleague, Michael Wysession, an associate professor of earth and planetary sciences at Washington University, called Haiti a "perfect storm."
"It's such an active field that Haiti should level Port-au-Prince and rebuild to the north," he said. "It's just going to keep happening there."
In this region, both scientists acknowledge some risk for seismic activity but believe it is much less than in other areas of world, such as California, Chile or Haiti.
"We know that there were large earthquakes here in the past, so there could be large earthquakes here in the future," Weins said. "I would say we have a moderate level of risk here."
Most recently, people remember feeling the ground move on April 18, 2008, from a magnitude 5.4 earthquake from the Wabash Valley Seismic Zone in southwestern Illinois, which might be picking up in activity.
Because of the kind of geological structures here, Weins said that seismic waves travel very efficiently in the Midwest, so that the area affected by an earthquake is larger than what it would be in, for example, California or Chile.
"We are getting good at forecasting earthquakes as to where and how big they might be," Wysession said. "We have no ability to predict when; that appears to be totally random."
Wysession observed that there hasn't been a magnitude 6 earthquake in the New Madrid Seismic Zone for more than a century or a magnitude 5 earthquake in more than 40 years.
"All indications suggest that its activity has tailed off," he said. "There no reason to believe that it will return to seismicity."
On average, Wysession said there is approximately one magnitude 7 earthquake each month somewhere around the globe and one magnitude 8 earthquake per year.
"I'm not saying we won't get an earthquake here, but there is no indication that the risk is higher here than in Wichita, Kansas, or Columbus, Ohio."
For more information about earthquakes, go to the U.S. Geological Survey's Earthquake Hazards Program site at www.earthquake.usgs.gov.
Area's earthquake risk explained
Located some 185 miles south of Alton in the Missouri Bootheel, the New Madrid Seismic Zone long has been a source of anxiety for area residents.
The New Madrid fault's most famous seismic activity, known as the New Madrid earthquakes, took place in 1811 and 1812. The series of three earthquakes and 27 aftershocks not only permanently changed the course of the Mississippi River but also caused church bells to ring in Boston, New York City and Washington, D.C.
Last Tuesday, the U.S. Geological Survey recorded a 3.7 magnitude earthquake near East Prairie in the Missouri Bootheel, again drawing attention to the fault zone's risk for the occurrence of a significant earthquake similar to the recent ones in Haiti and Chile.
"We get mag-3 earthquakes in the New Madrid region several times per year on average, so it is normal," said Michael Wysession, an associate professor of earth and planetary sciences at Washington University in St. Louis.
Capt. Tim Quigley of the Alton Fire Department said there were no reports Tuesday indicating that anyone in the area felt the earthquake.
The New Madrid fault is considered active, averaging more than 200 measured events per year (1.0 or more on the Richter scale), although there is an ongoing debate among scientists as to whether the fault continues to pose a significant hazard.
"The New Madrid fault is a zone of weakness, but it's one of many on the continent," Wysession said. "As an intra-plate region, it doesn't have a cycle of accumulation and release like we see in Chile."
Because seismic activity could cause significant damage, insurance companies such as Birmingham Shelter Insurance offer earthquake insurance.
Mandated by company policy, there is a 30-day waiting period for the issuance of any new insurance policy following any activity.
Agent Mark Birmingham noted that non-reinforced mortar structures cannot be insured, but homes with poured concrete or slab foundations can be.
"I would say that 25 percent to 30 percent of my customers have earthquake insurance," Birmingham said. "I try to offer it to everyone that qualifies, but not everyone elects to take it."
On average, earthquake insurance on a frame house costs approximately 34 cents per $1,000 of value, with a 15 percent deductible, and 60 cents per $1,000 on a brick house, also with a 15 percent deductible.
John Farley, professor emeritus of sociology at Southern Illinois University Edwardsville, advocates using common sense and complying with suggested building codes to reduce the risk from earthquake damage. He also believes some level of preparedness for an emergency response would be prudent, including having emergency supplies on hand as suggested by the American Red Cross at www.redcross.org.
"Take common-sense steps," Farley advised. "Preparing for one disaster can also help protect you against another, such as ice or wind storms."
kbassett@thetelegraph.com
http://www.thetelegraph.com/news/earthquake-37222-earthquakes-new.html
March 07, 2010 4:40 PM
By KATHIE BASSETT
<!-- Video goes here -->
In the aftermath of cataclysmic earthquakes in Haiti and Chile, residents are expressing renewed concern over the likelihood of an event occurring here.
Douglas Weins, chairman of the Department of Earth and Planetary Science at Washington University in St. Louis, cautioned against making broad assumptions regarding the potential for significant earthquake activity here based on recent events around the world, including the 3.7 magnitude earthquake that occurred last Tuesday in the New Madrid Seismic Zone in southeastern Missouri.
Weins emphasized that each of these earthquakes has occurred in different settings and need to be viewed as separate events, not part of a global pattern.
"It's extremely unfortunate that the two big earthquakes this year happened in densely populated areas," he said.
"In Chile, the earthquake occurred because the sea floor is slipping underneath the continent, so there is a rubbing," he said. "This is an inter-plate earthquake that was also connected to volcanic activity."
The situation in Haiti more closely resembles the setting in Chile than the one here in the Midwest, he explained further.
The New Madrid fault is located in the middle of the tectonic plate, not on plate boundaries like Chile and Haiti. The fault produces intra-plate earthquakes.
"It's really a crack in the plate, not part of a big seismic system like Chile," he said. "Haiti's earthquake was the result of different plates sliding past one another; the country is situated on a plate boundary."
In Haiti's case, Weins said it would be hard to think of a worse location for an earthquake to occur - under the capital city of one of the most impoverished nations in the Western Hemisphere. Even though the Chile earthquake was 100 times larger at magnitude 8.8 versus the magnitude 7.0 in Haiti, the damage was less severe, thanks to stricter building codes.
Wein's colleague, Michael Wysession, an associate professor of earth and planetary sciences at Washington University, called Haiti a "perfect storm."
"It's such an active field that Haiti should level Port-au-Prince and rebuild to the north," he said. "It's just going to keep happening there."
In this region, both scientists acknowledge some risk for seismic activity but believe it is much less than in other areas of world, such as California, Chile or Haiti.
"We know that there were large earthquakes here in the past, so there could be large earthquakes here in the future," Weins said. "I would say we have a moderate level of risk here."
Most recently, people remember feeling the ground move on April 18, 2008, from a magnitude 5.4 earthquake from the Wabash Valley Seismic Zone in southwestern Illinois, which might be picking up in activity.
Because of the kind of geological structures here, Weins said that seismic waves travel very efficiently in the Midwest, so that the area affected by an earthquake is larger than what it would be in, for example, California or Chile.
"We are getting good at forecasting earthquakes as to where and how big they might be," Wysession said. "We have no ability to predict when; that appears to be totally random."
Wysession observed that there hasn't been a magnitude 6 earthquake in the New Madrid Seismic Zone for more than a century or a magnitude 5 earthquake in more than 40 years.
"All indications suggest that its activity has tailed off," he said. "There no reason to believe that it will return to seismicity."
On average, Wysession said there is approximately one magnitude 7 earthquake each month somewhere around the globe and one magnitude 8 earthquake per year.
"I'm not saying we won't get an earthquake here, but there is no indication that the risk is higher here than in Wichita, Kansas, or Columbus, Ohio."
For more information about earthquakes, go to the U.S. Geological Survey's Earthquake Hazards Program site at www.earthquake.usgs.gov.
Area's earthquake risk explained
Located some 185 miles south of Alton in the Missouri Bootheel, the New Madrid Seismic Zone long has been a source of anxiety for area residents.
The New Madrid fault's most famous seismic activity, known as the New Madrid earthquakes, took place in 1811 and 1812. The series of three earthquakes and 27 aftershocks not only permanently changed the course of the Mississippi River but also caused church bells to ring in Boston, New York City and Washington, D.C.
Last Tuesday, the U.S. Geological Survey recorded a 3.7 magnitude earthquake near East Prairie in the Missouri Bootheel, again drawing attention to the fault zone's risk for the occurrence of a significant earthquake similar to the recent ones in Haiti and Chile.
"We get mag-3 earthquakes in the New Madrid region several times per year on average, so it is normal," said Michael Wysession, an associate professor of earth and planetary sciences at Washington University in St. Louis.
Capt. Tim Quigley of the Alton Fire Department said there were no reports Tuesday indicating that anyone in the area felt the earthquake.
The New Madrid fault is considered active, averaging more than 200 measured events per year (1.0 or more on the Richter scale), although there is an ongoing debate among scientists as to whether the fault continues to pose a significant hazard.
"The New Madrid fault is a zone of weakness, but it's one of many on the continent," Wysession said. "As an intra-plate region, it doesn't have a cycle of accumulation and release like we see in Chile."
Because seismic activity could cause significant damage, insurance companies such as Birmingham Shelter Insurance offer earthquake insurance.
Mandated by company policy, there is a 30-day waiting period for the issuance of any new insurance policy following any activity.
Agent Mark Birmingham noted that non-reinforced mortar structures cannot be insured, but homes with poured concrete or slab foundations can be.
"I would say that 25 percent to 30 percent of my customers have earthquake insurance," Birmingham said. "I try to offer it to everyone that qualifies, but not everyone elects to take it."
On average, earthquake insurance on a frame house costs approximately 34 cents per $1,000 of value, with a 15 percent deductible, and 60 cents per $1,000 on a brick house, also with a 15 percent deductible.
John Farley, professor emeritus of sociology at Southern Illinois University Edwardsville, advocates using common sense and complying with suggested building codes to reduce the risk from earthquake damage. He also believes some level of preparedness for an emergency response would be prudent, including having emergency supplies on hand as suggested by the American Red Cross at www.redcross.org.
"Take common-sense steps," Farley advised. "Preparing for one disaster can also help protect you against another, such as ice or wind storms."
kbassett@thetelegraph.com
http://www.thetelegraph.com/news/earthquake-37222-earthquakes-new.html