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Thursday, 22 November 2018 01:00

New insights about the seismic hazard of New Madrid area, Missouri

New insights about the seismic hazard of New Madrid area New insights about the seismic hazard of New Madrid area.

Scientists have attempted to shed light on the earthquake vulnerability of the area around New Madrid, Missouri.

About 200 years ago, the aforementioned region experienced a sequence of massive (about 8.0 magnitude) seismic incidents. These earthquakes resulted in building collapses and soil liquefaction. The final event, which was also the most severe, occurred on Reelfoot fault and altered the course of the Mississippi River.

Investigations have shown that other series of such earthquakes have been recorded earlier in this area. Therefore, New Madrid is characterized as an earthquake-prone zone for future events.

Ryan Gold of the U.S. Geological Survey (USGS) stated: "We know there were also large earthquakes at around 1450 AD and 900 AD." However, not all earthquakes occur along the Reelfoot fault. Gold assumed that the scrap linked with the Reelfoot fault shows that earthquakes haven't been sustained for a long time. "If earthquakes happen on the Reelfoot fault every 500 years, and have been doing so for hundreds of thousands of years, we would expect to see a mountain range there—but we don't," he commented.

To put Gold's theory to the test, USGS scientists decided to investigate deeper into the past. This procedure proved to be challenging as sustaining records from past earthquakes is a difficult task due to natural phenomena (e.g. rain and floods) and anthropogenic activity.

The researchers decided to study the hills of the Mississippi River, east of the Reelfoot fault. They noticed high concentration of depressions and they assumed that these depressions are cracks in the ground caused by big earthquakes.

A trench was excavated in one of the depressions that had formed in Peoria loess. According to USGS, the trench revealed four distinct packages of sediment which corresponded to earthquakes previously detected in Reelfoot's fault: 1812 AD, around 1450 AD, around 900 AD and around 2300 BC. Gold said: "Our record confirms that the tempo of earthquakes hasn't been sustained,".

USGS team believes that the results of the investigation can provide new insights concerning the seismic hazard of the region. It is possible that these data will provoke alterations and updates in the construction design codes.

Source: Geosociety.org

Read 150 times Last modified on Thursday, 22 November 2018 15:53

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