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I ran across an interesting but obscure article on the Internet the other day.  The title was “Researchers Complete Seismic Borehole In Kentucky”.  That’s odd, I thought, why would you drill a seismic borehole in Kentucky.  And then I remembered.  I was born and raised in Missouri, you see.

If I ask you what state in the union is most likely to be hit by big earthquakes, you’ll say “California”.  We all know that the San Andreas Fault is poised for disaster.  “Alaska” would also be a good answer.  The great Alaskan earthquake of 1964 was the largest earthquake in North America and the second largest ever recorded (the most powerful earthquake occurred in Chile in 1960).  The Alaska earthquake measured 8.6 on the Richter scale. But the largest earthquakes ever recorded for the continental US (excluding Alaska and Hawaii) didn’t happen in California.  There were three of them and they are all estimated to have been in excess of 8 on the Richter scale (the Great San Francisco earthquake of 1906 measured 7.8).  The earthquakes happened in the winter of 1811-1812 and the epicenter was the small town of New Madrid, Missouri.

The New Madrid Fault outlined in modern day earthquakes.

Survivors of these massive quakes reported that they caused cracks to open in the earth's surface, the ground to roll in visible waves, and large areas of land to sink or rise.  The crew of the New Orleans (the first steamboat on the Mississippi, which was on her maiden voyage) reported mooring to an island only to awake in the morning and find that the island had disappeared below the waters of the Mississippi.
These earthquakes, which occurred on 16 December 1811, and 23 January and 7 February 1812, were felt over the entire United States east of the Rockies.  This is over a million square miles (in contrast, the great San Francisco earthquake was felt over a 60,000 square mile area).  The shaking rang church bells in Boston and damage was reported as far away as Charleston, South Carolina, and Washington, D.C.  Forests were destroyed over an area of 150,000 acres.

According to eyewitness accounts, at the onset of the earthquake, the ground rose and fell and opened deep cracks in the ground.  There were landslides on most of the steeper bluffs and hillsides.  Large areas of land were uplifted; and still larger areas sank and were covered with water that emerged through cracks in the ground.  Huge waves on the Mississippi River sank many boats and washed others high on the shore.  High banks caved and collapsed into the river; sand bars and points of islands gave way and whole islands disappeared.

Contemporary woodcut of the destruction caused by the New Madrid Earthquakes

The region most seriously affected was characterized by raised or sunken lands, fissures, sinks, sand blows, and large landslides that covered an area of at least 60,000 square miles that extended from Cairo, Illinois, to Memphis, Tennessee, and from Crowley’s Ridge, Arkansas to Chickasaw Bluffs, Tennessee.

The course of the Mississippi River was significantly changed, and the gigantic earthquake of 23 January 1812 actually caused the largest river in the US to flow backward for several hours.  Half the houses in New Madrid were totally destroyed and the other half were uninhabitable.  "Houses, gardens, and fields were swallowed up" one source notes.  But fatalities and damage were low, because the area was sparsely settled then.

Unfortunately, the area is no longer sparsely populated.  Today, the region is home to millions of people, including those in the cities of St. Louis, Missouri, and Memphis, Tennessee.  Memphis is built on a high bluff overlooking the Mississippi River.  During the New Madrid earthquakes, many landslides occurred along the river and if you go ‘walkin’ in Memphis’, after a shaker like the New Madrid earthquakes, you’ll likely be doing it on the bottom of the Mississippi.  Adding to the danger, most structures in the region have not been built to withstand earthquakes. 

Unfortunately, geologists are accumulating more and more data that say this area has had many violent earthquakes in the past and will have them again in the future.  USGS scientists estimate that the probability for an earthquake along the New Madrid Fault of magnitude 6.0 or greater is significant in the near future, with a 50% chance by the year 2010 and a 90% chance by the year 2040.  An earthquake with a magnitude equal to that of the 1811- 1812 quakes could result in incredible loss of life and property damage in the billions of dollars. 

Which brings us to that borehole in Kentucky.  The hole is four inches in diameter and almost 2,000 feet deep and it’s very close to the most active part of the New Madrid Seismic Zone.  The location will allow instruments placed in the hole to gather the maximum amount of data from the region's earthquakes and allow geologists to better define the earthquake hazard in the region.

So, it isn’t just the Ring of Fire that has earthquakes.  Mother Earth has a whole lot of shakin’ going on!
Cruise on over to the Deep Website at www.thedeepradioshow.com to learn more about earthquakes and many other topics.  Enjoy!