Dozens of aftershocks follow earthquake
The Friday morning 5.2 magnitude earthquake was followed by dozens of aftershocks including a 4.5 magnitude one nearly six hours later.
Sheriff Dan Bullock said he felt the 5.2 earthquake, which occurred at 4:37 a.m. Friday. A short time later, he began receiving phone calls. He didn’t feel the 4.5 aftershock.
Bullock said no damage has been reported in the county.
Throughout Missouri, there were only scattered report of minor property damage.
“My office and the Department of Public Safety continue to monitor the impact of the earthquake and I have directed all state agencies to review their earthquake response plans,” Gov. Blunt said Friday afternoon. “The Missouri Department of Transportation activated inspection teams to evaluate Missouri’s roads and bridges along the eastern portion of Missouri …”
According to the Associated Press, Missouri Department of Transportation inspectors on Friday examined hundreds of bridges in the eastern part of the state, checking for possible damage from a moderate earthquake.
MoDOT planned to look at 2,500 bridges, all of them on Friday. By mid-afternoon, several hundred had already been evaluated, including Missouri River crossings at Hermann, Jefferson City, Boonville, Rocheport, Miami and Glasgow. No problems were found, the agency told AP.
The magnitude 5.2 quake just before 4:37 a.m. was centered in southern Illinois, about 130 miles from St. Louis. It awakened and startled residents in several parts of Missouri, including St. Francois County and neighboring counties.
Dozens of aftershocks, including one with magnitude 4.5 about 10:15 a.m., followed. But MoDOT told the AP that the aftershock wasn’t strong enough to damage a bridge, so re-examination of structures looked at earlier Friday wasn’t necessary.
There have been no reports of injuries or serious damage in Missouri. But one bridge that may have been damaged by the earthquake was an overpass on Kingshighway in St. Louis. Debris fell from the overpass around the time the earthquake happened.
Blunt ordered all agencies of the Department of Public Safety to be prepared to help in case of emergency.
Dave Overhoff, geo-hazards geologist with the Missouri Department of Natural Resources’ Division of Geology and Land Survey in Rolla said, “While the movement was along the Wabash Valley Fault System, this system is independent of the New Madrid Seismic Zone.”
The Wabash Valley Fault System runs perpendicular to the New Madrid Fault along the north end of the system.
According to DNR, moderately damaging earthquakes occur on the Wabash Valley fault about once every decade or two. Smaller earthquakes are felt about once or twice a year, which is considerably less active than the New Madrid Seismic Zone. The largest recorded earthquake on the Wabash Valley Fault System was in 1968, which registered magnitude 5.4. On June 18, 2002, a 5.0 magnitude earthquake struck the Evansville, Indiana, area.
Overhoff said that the New Madrid Seismic Zone is the country’s most active seismic zone east of the Rockies and produces more than 200 small earthquakes each year along the zone.
Most are too weak to be noticed by the public; however, the Center for Earthquake Research and Information in Memphis, Tenn., registered a magnitude 3.4 earthquake on Oct. 18, 2006, near New Madrid.
The New Madrid Seismic Zone extends 120 miles southward from the area of Charleston, Missouri, and Cairo, Illinois, through New Madrid and Caruthersville, following Interstate 55 to Blytheville and southward to Marked Tree, Arkansas. The zone crosses five state lines and cuts across the Mississippi River in three places and the Ohio River in two places.
In 1811 and 1812, the New Madrid Seismic Zone produced a series of earthquakes estimated at magnitude 7.0 or greater. Several thousand smaller earthquakes followed through mid-March. Fifteen of these quakes were magnitude 6.5 to 8 (the size range of the 1989 San Francisco, the 1994 Los Angeles and the 1995 Kobe, Japan, earthquakes).
Overhoff said, “A similar size earthquake occurring along the zone in this century has the potential to significantly impact not only Missouri but also residents in Arkansas, Illinois, Kentucky, Tennessee and Mississippi.”
The Missouri Department of Natural Resources and the Missouri Department of Health and Senior Services are advising Missouri residents to take precautions with their drinking water following the earthquake.
Due to the seismic activity, some public water systems and private well supplies may have experienced damage to well casings, cracked water lines, low water pressure, and in some cases, complete water outages. Low pressure and broken lines allow contaminants to enter drinking water, so people in these situations need to consider boiling their drinking water.
There have been no reports of water quality problems related to this event at this time, but residents should remain aware of the potential.
Because an earthquake can cause shifts in the earth, groundwater used for drinking and the private wells that access it can be affected. Well water can become cloudy or take on a different color, smell and feel. The water can also become contaminated with dirt, minerals and other solids, as well as bacteria. Do not use water that has a dark color, an odor or contains floating material.
If you have a private well for drinking water and you felt the earthquake, you should check your well water system for damage or for changes in your drinking water. If your well system is damaged or your well water changes, you should stop drinking it until the water clears and then have it tested for bacterial contamination. Consider drinking bottled or purified water until your well water is deemed safe to drink.
If you suspect your well water is contaminated, contact your local public health agency for information on water testing and for proper well disinfecting procedures. A listing of Missouri local public health agencies can be accessed at http://www.dhss.mo.gov/LPHA/LPHAs.html. More information on safe well water can be accessed on the DHSS Web site at http://www.dhss.mo.gov.
