Growing up in Southern Illinois near the Mississippi River, the natural hazards we faced tended to be weather or water related. But, teachers also made it clear to us that we could just as easily be threatened by rumblings from beneath our feet. As I learned, there was a series of massive earthquakes that happened in the early 1800’s in an area called the New Madrid Seismic Zone. From December 16, 1811, through February 7, 1812, a string of temblors with magnitudes estimated at 7.2 to 8.1 wracked the region. The severity of these events caused the Mississippi to “flow” backwards, change course, and result in the creation of new lakes, such as Reelfoot Lake in TN.
For a teenager, 1811 was ancient and the associated earthquakes were equally distant and improbable in the present. So imagine my surprise while at work in a clothing warehouse in downtown St. Louis on Saturday November 9, 1968, an earthquake happened. We didn’t know what it was. Major shaking of the many overhead metal clothing racks chased us outside where we had a chance to watch major buildings swaying. While not centered near the 1811-12 quakes, it was not far away, and, while only a 5.5 tremor, it seemed overwhelming in its power.
Spin forward to April 18, 2008, and the region was again visited by a potent quake. According to news stories this event, a 5.2, was the most powerful since the one I experienced 40 years earlier…
…and with these temporally separated events as backdrop, I decided to do a little geographic work with ArcGIS Explorer.
“Exploring a Midwest Earthquake Zone with ArcGIS Explorer: Part II” will be published April 23, 2008.
- George Dailey, ESRI Education Manager