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Thursday, 22 September 2016 01:00

Researchers Develop Theory Behind New Madrid Earthquakes

New Madrid Seismic Zone diagram New Madrid Seismic Zone diagram. Credits: C. Bickel / Science

Researchers along with USGS believe they may have developed a theory to explain the mid-plate earthquakes of the New Madrid Seismic Zone. They theorize that super dense rock exerts a gravitational pull on the terrain above creating a higher likelihood that faults in the NMSZ will slip.

In the early 1800's, several massive earthquakes rocked the area that would later be known as the New Madrid Seismic Zone in southeastern Missouri. Three earthquakes in particular are believed to have measured above a magnitude 7.0 making them the largest known earthquakes in the United States east of the Rocky Mountains. The quakes toppled buildings and shook even more constructions up to 1000 km away.

While most large quakes occur near active faults, the New Madrid events are unique in that they occurred in the middle of the North American Plate. The researchers believe that blobs of super dense rock-plutons-from the lower crust are exerting a gravitational pull on their surroundings. However, this alone might not explain the events. The scientists also believe that there may be ancient rifts beneath the New Madrid Seismic Zone caused when the plate broke away from the supercontinent millions of years ago. These rifts allow the plutons to rise closer to the surface. They further theorize that erosion of the Mississippi River Valley decreased the weight locking the faults in place, allowing them to move more freely.

The USGS obtained seismic velocity data from the U.S. Transportable Array, a seismometer grid. They hope that this same method could be used to identify other areas that could be prone to seismic activity, but further research and analysis is needed.

Source: Science Mag

Read 1312 times Last modified on Tuesday, 04 October 2016 13:47

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