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Transcript for Hidden Fury, segment 09 of 11
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Landslides and liquefaction are triggered by strong shaking during earthquakes. By itself, shaking is a serious threat to weak structures. Most vulnerable are old bridges and unreinforced masonry buildings built on loose ground. Unfortunately, many historic ornate buildings around the New Madrid Earthquake zone fall under this category.
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When most of us think of earthquakes, we picture gaping fissures like this one. This is indeed a common scene when a quake strikes California. The Landers Quake in nineteen ninety-two opened a fissure fifty miles long across the floor of the Mojave Desert, but the faults of the New Madrid quake zone are too deeply buried to rupture the ground except in massive quakes. Liquefaction, shaking, and landslides are the main effects of earthquakes in this region, and the city most threatened by earthquakes is the Blues Music Capital of the World, Memphis.
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As musicians play on Beale Street, scientists from Memphis State University are evaluating Shelby County's public buildings and bridges for earthquake safety. Preliminary results are sobering. One out of four hospitals are in the highest seismic risk category. Twenty-five percent of the public schools and fifteen percent of the fire stations also fall in this category. A sampling of the county's nine hundred bridges show that one out of four are at the highest level of risk. Seismic evaluation of public utilities and other critical lifelines is also underway. These studies will guide the strengthening of only the most dangerous and critical structures. Retrofitting is expensive, and there are a great number of weak facilities.
On the other hand, building new buildings to be earthquake safe raises construction costs only ten percent on average, but earthquake codes are weak to nonexistent in the New Madrid quake zone. The state of Kentucky is an exception. They adopted modern earthquake codes in nineteen eighty-one, and recently surrounding states are taking earthquakes more seriously. Researchers found new evidence of one or more massive quakes near Vincennes, Indiana. The large cities of Indianapolis and Evansville are less than one hundred miles away. Chicago, Illinois, built on a veneer of very loose lake muds, is two hundred miles away. Skyscrapers are in danger of excessive swaying from low frequency, high amplitude seismic waves.