The New Madrid Fault delivered two earthquakes only six hours apart today in 1811. Now WE know em

New_Madrid_Erdbeben

The New Madrid Seismic Zone, sometimes called the New Madrid Fault Line, is a major seismic zone and a prolific source of earthquakes near New Madrid, Missouri.

The 150-mile long fault line extends into five states, and stretches southward from Cairo, Illinois; through Hayti, Caruthersville and New Madrid in Missouri; through Blytheville into Marked Tree in Arkansas. It also covers a part of West Tennessee, near Reelfoot Lake, extending southeast into Dyersburg.

Most of the seismic activity is generated between 3 and 15 miles beneath the Earth’s surface.

December 16, 1811

In 1811, New Madrid was the largest settlement on the Mississippi River between St. Louis, Missouri and Natchez, Mississippi.

Then at 2:15 a.m. local time on December 16, 1811, a massive earthquake hit with an epicenter in northeast Arkansas.

This first quake alarmed the population but caused only slight damage to man-made structures, mainly because of the sparse population in the area, however it was felt over 372,822 square miles.

People were awakened by the shaking as far away as New York City.

Then six hours later at about 7:15 am. Another quake hit near New Milford, Missouri with the same or perhaps an even greater intensity as the earlier one.

Perceptible ground shaking was in the range of one to three minutes depending upon the observers location.

Trees were knocked down and riverbanks collapsed. This second event shook windows and furniture as far away as Washington, D.C., rang bells in Richmond, Virginia, sloshed well water and shook houses in Charleston, South Carolina, and knocked plaster off of houses in Columbia, South Carolina.

In Jefferson, Indiana, furniture moved and in Lebanon, Ohio, residents fled their homes.

Observers in Herculaneum, Missouri, called it “severe” and claimed it had a duration of 10–12 minutes.

The earthquake caused the ground to rise and fall – bending the trees until their branches intertwined and opening deep cracks in the ground. Deep seated landslides occurred along the steeper bluffs and hillsides; large areas of land were uplifted permanently; and still larger areas sank and were covered with water that erupted through fissures.

The earthquake also gave the waters of rivers including the Mississippi the illusion of flowing upstream towards St. Louis. To the south, even the future location of Memphis, Tennessee was shaken.

Huge waves on the Mississippi River overwhelmed many boats and washed others high onto the shore. High banks caved and collapsed into the river; sand bars and points of islands gave way; whole islands disappeared. Boatman John Bradbury, who was moored to a small island south of New Madrid, described the second quake as “terrible, but not equal to the first”.

The region most seriously affected was characterized by raised or sunken lands, fissures, sinks, sand blows, and large landslides that covered an area of 50,000 – 80,000 square miles, extending from Cairo, Illinois, to Memphis, Tennessee, and from Crowley’s Ridge in northeastern Arkansas to Chickasaw Bluffs, Tennessee.

Only one life was lost in falling buildings at New Madrid, but chimneys were toppled and log cabins were thrown down as far distant as Cincinnati, Ohio, St. Louis, Missouri, and in many places in Kentucky, Missouri, and Tennessee.

At least three other large aftershocks are inferred from historical accounts on December 16 and 17, 1811. Reports also indicate that people felt minor aftershocks every six to ten minutes and was thus nicknamed “The Daylight Shock.”

Today it is estimated that the first earthquake was a magnitude of around 7.7 and the second somewhere between a magnitude of 7.2 and 8.2

 January 23, 1812

Then a third earthquake struck New Madrid, Missouri at 9:15 a.m. on January 23 with an estimated magnitude of 7.5.

It is difficult to assign intensities to the principal shocks that occurred after 1811 because many of the published accounts describe the cumulative effects of all the earthquakes and because the Ohio River was iced over, so there was little river traffic and fewer human observers.

Using the December 16 earthquake as a standard, however, there is a general consensus that this earthquake was the smallest of the three principals.

 February 7, 1812

Then a fourth and final earthquake struck New Madrid, Missouri with an estimated magnitude of 7.7.

Several destructive shocks occurred on February 7, the last of which equaled or surpassed the magnitude of any previous event.

The town of New Madrid was by now utterly destroyed.

At St. Louis, many houses were again damaged severely and remaining chimneys were thrown down.

These were the largest earthquakes in the United States since its settlement by Europeans.

The area of strong shaking associated with these shocks were two to three times as large as that of the 1964 Alaska earthquake and 10 times as large as that of the 1906 San Francisco earthquake.

Because there were no seismographs in North America at that time, and very few people in the New Madrid region, the estimated magnitudes of these series of earthquakes vary considerably and depend on modern researchers’ interpretations of journals, newspaper reports, and other accounts of the ground shaking and damage.

Today, there is still the potential of large earthquakes in this area sometime in the future, threatening parts of seven states.

Now WE know em

 568px-New_Madrid_Seismic_Zone_activity_1974-2011_svg (2)

 

 

Advertisements

Please Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s