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Transcript for Hidden Fury, segment 05 of 11
At the edge of many crustal plates, the landscape reflects the violence of rocks grinding together. California straddles the boundary between the North American and Pacific Plates. The rugged landscape is geologically very young, and seismic waves break up quickly in the broken landscape they created, but there are exceptions.
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October seventeenth, nineteen eighty-nine. San Francisco's Marina District was heavily damaged by the Loma Prieta Earthquake, but the quake's epicenter was over sixty miles away. In between, the heavily populated Bay Area suffered relatively little damage. The Marina District was hard-hit because it is built on very soft sand and mud. Ironically, part of it was once a lagoon which was filled in with sand and rubble from the nineteen oh six earthquake. Seismic waves sped away from the Loma Prieta quake's epicenter through hard bedrock below, but nearing the marina, they slowed down in the loose surface materials. This caused the waves to grow into destructive surges at ground level.
The New Madrid earthquake zone lies buried in the Mississippi River Valley. Connecting with the river is a vast network of more rivers, streams, and lakes, all draining the wet climate of the midcontinent. These waterways eroded the land and left valleys of loose sediment over hard crustal rocks below, a dangerous combination. Seismic waves travel great distances through the rigid crust, then build to violent force in soft river valley sediments. By coincidence, this is where most people live.
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The face of the New Madrid Earthquake Zone has changed dramatically since the great quakes of eighteen eleven and twelve. The region has become a major agricultural and industrial producer. The busiest transportation corridor in the nation, the Mississippi River, winds its way through. Crowded interstate highways and a dense web of railroads crisscross the earthquake zone. Below ground, natural gas and oil pipelines connect refineries in the south with customers in the northeast where one-quarter of the nation's energy is consumed. In Memphis Elvis Presley's Graceland attracts more visitors than any other home in America except the White House, and Memphis Airport serves as distribution headquarters for the world's biggest freight carrier.
The wilderness of eighteen eleven and twelve is indeed gone, and as the works of people replaced it, the New Madrid earthquake zone remained silent so the area grew up unarmed against the fury of earthquakes.
When an earthquake does happen in central and eastern U. S., the damage areas are going to be a lot bigger, and it's going to be a higher density of damage than you would see for a similar size earthquake in California. Most of the buildings in central and eastern United States are constructed from unreinforced masonry which has virtually no resistance to strong ground shaking. In fact, the last major earthquake that happened in central and eastern U. S. was in eighteen ninety-five when we developed this whole new infrastructure. Since then, it hasn't been tested by a strong damaging earthquake the same way that California gets, seems to get tested every ten or twenty years. There's a strong earthquake that knocks down buildings, and they put up new ones that are designed to withstand or resist those forces better, but we haven't had the benefit of that kind of testing in the central and eastern U. S. so when one finally does happen, the, the projection of the damage is going to be a lot more serious.