NEW MADRID, Missouri -- Sometimes serendipity strikes and you manage to be right where you should be exactly when you should be there.
As we headed toward New Madrid to check out the site of three of the most powerful earthquakes in U.S. history, a local radio station reported that a small earthquake -- magnitude 2.5, according to the National Earthquake Center -- had just been reported near the northern end of the New Madrid fault line.
Locals said they thought it was a storm at first. They heard what they thought was thunder, and their windows rattled. We thought we felt a bit of a shiver underfoot, but had put it down to lack of sleep and overactive imaginations, since we'd just been reading about the New Madrid earthquakes of 1811 and 1812 the night before.
We assume that no one thought what happened here on Dec. 16, 1811, was a figment of their imagination or a storm, though survivors' accounts do mention hearing a terrible thunderous roar when the earthquake began at about 2 a.m.
Survivors also describe seeing the earth swell and heave in a way that reminded them of waves on a stormy sea before huge cracks split the ground wide open in many places.
There were actual waves on the Mississippi River that morning, huge waves that swept north, against the river's natural flow, giving the impression that the river had changed course and was running backward. Boats along the river capsized under the weight of these waves, and their crews drowned.
The first pleasure steamboat to cruise the Mississippi river, the New Orleans, had embarked on her maiden voyage Dec. 15. At dusk, she tied up at an island in the middle of the river. Hours later the boat was nearly swamped by huge waves. One of the crew said he had never encountered such waves during his previous two decades at sea.
Damage from the Dec. 16 quake was reported as far away as Charleston, South Carolina, and Washington, D.C. And that was just the first of three magnitude 8 (or thereabouts, no one was measuring back then) earthquakes. A second quake struck hours later, and a third hit on Jan. 23, 1812. A fourth -- the biggest of all -- followed two weeks later on Feb. 7. After the Feb. 7 earthquake, the town of New Madrid was completely destroyed. It had been 25 feet above river level but was only 12 feet above after the earthquake.
Between the four major quakes, there were thousands of aftershocks. It is not known how many were killed or injured in the earthquakes, but casualties were probably few only because the area was sparsely populated.
Despite this history, scientists at the recent National Earthquake Conference, held this year in St. Louis, said they have a hard time convincing people that major earthquakes aren't just a problem for the western United States. The central Mississippi Valley has its own, oft-ignored active fault line, the New Madrid seismic zone, which runs from around Cairo, Illinois, along the Mississippi River to Marked Tree, Arkansas.
According to a paper prepared by researchers at the Central United States Earthquake Consortium, a "sizable quake, such as the ones in 1811 to 1812, would cause extensive devastation and loss of life. The cities of Memphis, Tennessee, and St. Louis, Missouri, would be hit head-on. There would be enormous damage in Kentucky, Ohio, Illinois, Arkansas, Indiana and Mississippi. Yet, some people in these areas are barely aware that the possibility of a major earthquake exists."
One of the issues raised at the National Earthquake Conference was that quakes along the New Madrid seismic zone affect much larger areas than earthquakes of similar magnitude in the western United States, due to geological differences in the two regions.
Most earthquakes -- like those in California and Japan -- occur where earth's plates grind past each other, drifting on the planet's hot mantle. The ground in such places is warmer and slightly elastic from the heat generated within the earth's core.
But the New Madrid Fault is not located near one of the several large tectonic plates, and the ground is cold and brittle. When the earth here moves, its lack of flexibility amplifies rather than absorbs seismic activity. The Central United States Earthquake Consortium offered the example of the San Francisco earthquake of 1906 (magnitude 7.8) which was felt 350 miles away in the middle of Nevada, but the temblors sent out from the New Madrid earthquake of December 1811 (estimated magnitude 7.5 to 8.0) caused church bells to ring in Boston, 1,000 miles away.
Scientists are divided over whether the "big one," the mother of all earthquakes that many predict is coming, will happen on the West Coast or the central Mississippi Valley. Some predict that New Madrid is the most likely spot. The Central United States Earthquake Consortium believes there is a 90 percent chance of at least a magnitude 6 or 7 earthquake hitting the Mississippi Valley within the next 50 years.
A study by a team led by Karl Mueller, a professor at the University of Colorado at Boulder, shows the New Madrid seismic zone is active and a real threat.
The research team hired backhoe operators to dig long, deep trenches in the floodplain of the Mississippi River in west Tennessee's Reelfoot Lake region, exposing recent deformation in the sediments. The activity that's shoving the earth around underground indicates that a major earthquake could be building up in the area, Mueller said.
Mueller's team also used an imaging technique adapted by former Boulder graduate student Adam Bielecki to produce 3-D topographic relief maps of the area that clearly show the small hills, bumps and wrinkles caused by seismic activity.
"For the first time we can begin to see how fast the earthquake engine is running and how long it takes to build up energy for a quake," said Mueller, who warns that "if an event similar to the 1811 and 1812 earthquakes occurs in the future, Memphis and St. Louis would be the hardest hit. And if the Mississippi River was running high at the time, there is the possibility of broken levees along some 150 miles of the river." The levee breaks would lead to major flooding.
Mueller hasn't yet made any predictions regarding when and how big the next New Madrid fault line earthquake might be. Eugene Schweig, of the U.S. Geological Survey, one of the coordinators of the Earthquake Hazards Program for the eastern United States, said research indicates there is only a 7 percent to 10 percent chance of a major earthquake happening in the central Mississippi Valley within the next 50 years. He believes the probability of a magnitude 6 quake happening within the next 50 years is between 25 percent and 40 percent.
Schweig, who lives in Memphis, said at the conference that people shouldn't worry about earthquakes but should instead invest their energy into preparing for them. Earthquake education -- how to protect yourself when the ground starts rocking and rolling -- is now part of the public school curriculum in many central Mississippi Valley public schools. Scientists are also running computer simulations to try to discover what structures would be likely to be impacted by a quake in order to shore up the appropriate buildings, roads and bridges.
Another problem with the New Madrid seismic zone is that it is an "intraplate fault" located in the middle of the North American plate and hidden under deep layers of sediment, unlike the San Andreas fault, large parts of which are clearly visible.
"Intraplate zones are something of a mystery," said geophysicist Paul Segall of California's Stanford University. "We can't even map the New Madrid fault, so we don't really know how big it is."
To assist researchers in learning more about the New Madrid fault line, and other really hot spots, the National Science Foundation has recently launched EarthScope, a $200 million venture intended to, as the foundation describes it, "take the earth's vital signs."
EarthScope features two networks of sophisticated information-gathering instruments. One is centered in an observatory deep within the San Andreas fault and is expected to provide direct measurements of the physical state and mechanical behavior of one of the world's most active faults.
The other network, which will eventually cover the entire United States, will utilize global positioning satellite receivers, strain meters to measure stretching and squeezing of the ground near active faults, and satellite radar imagery to measure and map the smallest movements across faults, the magma movement inside active volcanoes and the very wide areas of deformation associated with plate-tectonic motion.
"With these networks, scientists will get to measure previously undetected movements in Earth's twitchy skin and learn about the interactions between shifting continental plates and Earth's magma, the sea of molten rock beneath," said Margaret Leinen, assistant director of geosciences for the National Science Foundation.
*Wired news reporter Michelle Delio and photographer Laszlo Pataki have begun their four-week, geek-seeking journey along the Great River Road. If you know of a town they should visit, a person they should meet, a weird roadside attraction they have to see or a great place to fuel up on chili mac, barbecue, gumbo, boiled mudbugs and the like, please send an e-mail to *[email protected].
