It won’t take a catastrophic earthquake to do catastrophic damage Gary Patterson, USGS
June 18, 2006
AP
Kansas City
BLYTHEVILLE, Ark. – An earthquake expert with the U.S. Geological Survey says
many residents and officials in northeast Arkansas are setting themselves and
their neighbors up for a worse disaster by underestimating the results of a
quake in the region.
“This is a different kind of earthquake,” said Gary Patterson of the United
States Geological Survey Center for Earthquake Research and Information at the
University of Memphis in Memphis, Tenn.
“This is not a California earthquake,” Patterson said last week at a meeting
of the Arkansas Gov.’s Earthquake Advisory Council. “There are some basic
differences here that drive the hazard level up.”
Patterson, who serves as information director and geologist for the Memphis
center, said that, unlike faults in California, the New Madrid Seismic Zone
contains three to five major fault segments lying over the top of each other in a
relatively small area.
The zone stretches from northeast Arkansas and northwest Tennessee up into
southeast Missouri, far western Kentucky and southern Illinois.
Big earthquakes have happened before and will happen again in this area, he
said, citing the series of quakes in 1811-1812 that were the strongest ever to
occur in the continental United States.
But he said even a 6.5-magnitude quake has the potential of doing an enormous
amount of damage in Blytheville and Mississippi County, Patterson said.
“It won’t take a catastrophic earthquake to do catastrophic damage,” he said.
One of the most potentially damaging effects of an earthquake in this area,
Patterson said, will be liquefaction of soil near the surface. Huge areas of
sand in fields that are visible throughout the region are evidence of
liquefaction in past earthquakes, he said.
Patterson said liquefaction is expected to happen mostly in the places where
the Mississippi River has moved around, depositing sandy silt and gumbo clay.
In these areas, the water table is 6 feet or less below the surface of the
ground, and a quake will send the water to the surface, creating quicksand and
eliminating the soil’s ability to support loads.
During the first 72 hours after a significant quake of any magnitude,
Patterson said people will need to be rescued from collapsed buildings. He said 11
million people live in the New Madrid Seismic Zone, and a response plan is
needed to get “boots on the ground” during that period.
Patterson said he was recently visited by a Japanese diplomat who wanted to
know if it was a good idea to build a truck plant in northeast Arkansas.
“It is a good idea when things are built to proper codes,” he said. “The name
of the game is building structural type. We all have to be on the same page
when we talk to these people.”
http://www.kansascity.com/mld/kansascity/news/local/14849167.htm