Midwest quake zone
Map locates approximate epicenter, extent and seismic zone of origination of a magnitude-5.2 earthquake in the Midwest on April 18, 2008
The Reelfoot Rift goes back about 750 million years, to when the entire landmass of the earth constituted a single supercontinent, designated now as Rodinia. At the time a constructive fault zone began to form, now called the Reelfoot Rift, but it failed, and the zone became inactive.
About 550 million years later, at the time of the supercontinent called Pangaea, the fault zone again became active but no longer functioned as a constructive plate and remains in the same condition today. The earthquakes are therefore traced to seismic activity 5 to 25 kilometers (3-15 mi) below the crust of the earth.
Government warns of “catastrophic” U.S. quake
Thu Nov 20, 2008 6:42pm EST By Carey Gillam
KANSAS CITY, Missouri (Reuters) – People in a vast seismic zone in the southern and Midwestern United States would face catastrophic damage if a major earthquake struck there and should ensure that builders keep that risk in mind, a government report said on Thursday.
The Federal Emergency Management Agency said if earthquakes strike in what geologists define as the New Madrid Seismic Zone, they would cause “the highest economic losses due to a natural disaster in the United States.”
FEMA predicted a large earthquake would cause “widespread and catastrophic physical damage” across Alabama, Arkansas, Illinois, Indiana, Kentucky, Mississippi, Missouri and Tennessee — home to some 44 million people.
Tennessee is likely to be hardest hit, according to the study that sought to gauge the impact of a 7.7 magnitude earthquake in order to guide the government’s response. In Tennessee alone, it forecast hundreds of collapsed bridges, tens of thousands of severely damaged buildings and a half a million households without water. Transportation systems and hospitals would be wrecked, and police and fire departments impaired, the study said.
The zone, named for the town of New Madrid in Missouri’s southeast corner, is subject to frequent mild earthquakes. Experts have long tried to predict the likelihood of a major quake like those that struck in 1811 and 1812. These shifted the course of the Mississippi River and rang church bells on the East Coast but caused few deaths amid a sparse population.
“People who live in these areas and the people who build in these areas certainly need to take into better account that at some time there is … expected to be a catastrophic earthquake in that area, and they’d better be prepared for it,” said FEMA spokesperson Mary Margaret Walker.
(Editing by Andrew Stern and Xavier Briand)
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