- Robert Nelson,
ISU professor of geology
As Japan continues struggling to salvage and stabilize regions of the country that were devastated by the March 11, 9.0 earthquake and subsequent tsunami, many other parts of the world are re-evaluating their own preparedness for such a disaster. The shocking images coming from the country are reminders of just how powerful and unpredictable earthquakes can be and how even a country as earthquake-aware as Japan is vulnerable.
Here in the Midwest most people are probably not too concerned about earthquakes, primarily because the earthquakes that do occur are not significant enough to be felt over a large area. However, some would be surprised to learn that one of the most dangerous fault systems in the country lies just south of Illinois.
The fault system, known collectively as the New Madrid seismic zone, consists of numerous weak spots in the crust of our continent and extends southward from Cairo, Illinois 150 miles through Missouri, Arkansas, Kentucky and Tennessee. The seismic zone is named after New Madrid, a small town in Missouri that was destroyed by a series of earthquakes that took place in the winter and spring of 1811 and 1812. Although seismic readings were not possible at the time, the earthquakes are still considered some of the strongest ever on the North American continent.
Though the country was sparsely populated at the time, the earthquakes were significant says, ISU professor of geology, Robert Nelson.
“It was a big event for those people who experienced it,” Nelson said.“It was actually felt clear up in southern Quebec.”
The quakes were reportedly powerful enough to ring bells in Charleston, North Carolina and, by some accounts, temporarily reversed the flow of the Mississippi river.
“The whole area (New Madrid) came up about twenty feet,” Nelson said. “So what’s the river going to do? Now we’re changing, temporarily, the grade of the river.”
According to the United States Geological Survey, (USGS) huge waves appeared on the Mississippi River and overwhelmed many boats tossing some high on the shore. Massive sections of riverbank collapsed into the water and whole islands disappeared. The USGS went on to say that, few houses within a 250-mile radius of New Madrid remained undamaged. Those projections bring the damage zone into the Bloomington-Normal area.
While no earthquakes of that magnitude have occurred in the area since, the area remains the most seismically active in the United States east of the Rocky Mountains and has produced thousands of smaller quakes since.
As far as another big quake occurring in the area, Nelson consults a graph that illustrates a consistent pattern in the New Madrid zone.
“If you look at this,” Nelson said, “and say, ‘oh we’ve got this time and it’s getting shorter and shorter between them,’ then it would put them at every 200 to 250 years.”
What Nelson means is that it’s about time for another big quake and he’s not so sure the Midwest is prepared.
Seated in front of his computer screen, Nelson pulls up an aerial view of Memphis, Tennessee and points to a large section of the city running parallel and East of the river.
“This stuff is all built on wind blown material,” Nelson said. “This stuff will shake and rattle and collapse.”
The “stuff” Nelson refers to is sand and sediment that has accumulated from wind and river deposits and landfill brought in by the construction of the area. These are the kinds of substrates that do not fare well in earthquakes.
Nelson focuses the aerial view in closer and points out a large hospital in the middle of the area.
“Saint Jude’s,” Nelson said. “It’s in a bad spot.”
Another bad spot, according to Nelson, is the St. Louis area. Examining a map of the city, Nelson ponders their chances.
“St. Louis itself is on rock,” Nelson said. “That’s alright.”
Nelson then points to East St. Louis.
“This is on about 120 feet of sand and gravel. That wouldn’t make it,” Nelson said. “In essence, you could just basically write off that whole area.”
As far as the Bloomington-Normal area, Nelson isn’t as worried.
“We would experience it,” he said. “The damage is related to a whole lot of variables. A wood frame house is highly earthquake resistant because it flexes. As you move to more rigid construction; buildings originally made of brick, those are more vulnerable.”
At ISU, Nelson has determined a range of likely success.
“Our most earthquake resistant building on campus is Watterson Towers,” Nelson said, “because it was designed to account for wind sway. Our least earthquake resistant building on campus is Cook Hall.”
Earthquakes probably don’t enter the minds of most ISU students, especially if they grew up in Illinois. Andy Black, a mass communication major who is an Illinois native, has had very little experience with them.
“Earthquakes are few and far in between,” Black said. “The only one I remember was in 2008 and it was pretty small. There’s more of a concern about tornados around here.”
Though earthquakes don’t readily come to mind for your average ISU student, there are those on campus who have to consider the possibility. Don Kunde is the ISU assistant director of environmental health and safety and his job is to be prepared for such an event.
“The New Madrid is obviously the big one,” Kunde said. “Though there are quite a few faults in the Illinois area. If it’s a big one, it’s going to effect us. What we do is exercise our emergency action plan. That’s for all hazards, it doesn’t matter if it’s an earthquake or a tornado, we would respond pretty much the same way.”
Nelson says the state is trying to adopt uniform strategies in order to be more prepared in case of a major earthquake.
“This year is the first time that they’re trying to do a state-wide drill for earthquake preparedness,” Nelson said. “So at 10:15, April, 28, we’re going to have an earthquake.”