Can it Happen Here?
With the recent earthquake & tsunami in Japan, we have to wonder if it could happen here. The 100LB gorilla in the midwest, of course, is the New Madrid seismic zone which will mark the 200th anniversary of it's last shift this winter.
From December 1811 to February 1812 There were several strong quakes - the strongest recorded in the midwest and a number of smaller shakes. Minor shakes continued on til March of 1813. Near the epicenter New Madrid was flattened, earth liquified, geysers of earth and water erupted & 15-20 foot waves were reported on the Mississippi. Vibrations were felt in Michigan and in Boston where the shaking caused bells to ring.

This map uses the Modified Mercali Scale. It doesn't really measure anything it just kinda codifies the reported effects.
For all the power of the quakes they didn't do a whole lot of damage because there just wasn't a whole lot to damage. As late as 1830 Frances Trollope described Memphis as a few wooden buildings carved out of the forest on a bluff overlooking the river. Cincinnati only had a population of a little over 2,300. The city consisted of just over 1,000 structures in an area that would roughly be the central business district and Queensgate today. The structures were primarily 1 & 2 story wood buildings about a quarter of the buildings were brick and there were about 2 dozen buildings made of stone. The brickwork was about the only thing to suffer in Cincinnati. Cracks in walls were reported, some chimneys toppled & a bucket of water fell over. Light was obtained from candles and oil lamps but apparently this caused no problem.
Modern experts on buildings & seismology tell us that modern buildings in Cincinnati, which have added steel to the construction mix, should be structurally adequate for another quake from that region. The problem would be what the buildings are built on. Landslides on Cincinnati's soft hillsides would be a major problem. Of course since 1811 we have also networked ourselves with electric lines, phone lines, water lines, gas lines & bridges. Ruptures of gas lines & downed power lines could result in fires, Ruptured water lines and collapsed roadways could severely hamper emergency crews.
Quakes in the New Madrid area have happened before around 900, & 1500. Following this pattern we should have had another around the second half of the 20th century. The quakes in 1811 were preceded by intense flooding near the epicenter. Maybe modern river management has abated the potential for a major quake along the Mississippi?
There was a quake in Anna, Ohio in March after the flooding of the Ohio & Mississippi rivers in 1937 but Anna was nowhere near the rivers.
The earthquake of 1811 was also preceded by a comet visible in Cincinnati in September and strange solar activity noted by Dr Daniel Drake. He also noted in the days prior to the quake, a darkening of the sky.
What is scary, now, in Japan is the damage at it's nuclear power plants. In southern Ohio a nuclear plant would likely be built along the Ohio river. Drake pointed out tremors were more severe along the river bed. Would modern building techniques be strong enough to weather an 1811 strength quake? I would hope so. I certainly wouldn't build a plant anywhere near New Madrid, tho. Of course people have......

Natural and Statistical View, or a Picture of Cincinnati and the Miami Country by Daniel Drake
Cincinnati Magazine article 10/08

HT to Losantville

Also in Drake's treatise he also mentions the fate of the county courthouse that preceded the courthouse destroyed in 1884. It was burned down in a mishap in 1812. I'd love to see the insurance policy on the latest courthouse. :-)