Minor earthquakes rattle parts of Arkansas
A series of minor earthquakes shook an area north of Little Rock, Ark., throughout Monday and were large enough to be detected by seismic equipment at Louisiana Delta Community College in Monroe.
The largest earthquake was detected around 8:30 a.m. Monday and registered 3.8 magnitude on the Richter Scale, where a 1.0 is a small earthquake and 9.0 is a major earthquake. Since the area where the earthquakes were taking place is less than 200 miles from Louisiana, there is a theoretical chance that the Monroe area could feel the aftershocks from a large earthquake in central Arkansas.
Delta Associate Professor of Science Don Wheeler, who has analyzed the earthquake data in Arkansas, said the earthquakes were occurring southeast of a major seismic zone in northeastern Arkansas.
"A vast majority of the earthquakes have been on the small end of the spectrum, so we're not looking at some major events," Wheeler said. "We would not feel that here in Monroe. It would have to be in excess of 5.0 before we would feel anything of that magnitude."
Wheeler began monitoring the Arkansas earthquakes over the past weekend. Delta's Science Department operates an extensive array of seismic monitoring sites in the region.
According to U.S. Geological Survey data, there have been 19 recorded earthquakes north of Little Rock since Sunday, ranging in magnitude from 1.0 to 3.5. Monday's 3.8-magnitude earthquake occurred nearly four miles below the Earth's surface.
Most of them have come from an area known as the Enola Swarm — a seismically active area named after the town of Enola.
"Over 40,000 events have occurred in this area since 1982," Wheeler said. "This would probably be the third swarm that I could find, with a big one in 1982 and another swarm in 2001."
The earthquakes are taking place near what scientists call the New Madrid seismic zone, which is the most seismically active in North America east of the Rockies. The zone is primarily in southeastern Missouri, but includes a large part of northeastern Arkansas and western Tennessee.The network of faults in the New Madrid seismic zone is buried beneath hundreds to thousands of feet of sand and mud. In 1812, a magnitude 7.4-8.0 earthquake destroyed the town of New Madrid and severely damaged many homes in St. Louis, Mo.
While the geologically active area in north central and northeastern Arkansas lies just over 200 miles from northeastern Louisiana, Wheeler said it would take a considerably larger earthquake to affect any area in the area. However, there is always the possibility that a larger earthquake in Arkansas could cause structural damage to buildings in Louisiana, Wheeler said.
"What's unique is that generally speaking you feel an earthquake a greater distance in the eastern part of the United States than in the west simply because it's an older part of the continent and the Earth is more compact, so the earthquake travels more efficiently," Wheeler said. "If you had a major, catastrophic event on the New Madrid seismic zone with a magnitude of 7 or higher, then the potential would exist to have significant seismic shaking as far south as the Monroe area and structures here are built to handle that.
"It's not out of the realm of possibility that we could experience shaking in northeastern Louisiana as a result of a major earthquake on the New Madrid (seismic zone)."Source
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