021010 Haiti Earthquakes Raise Questions about Reelfoot Lake and New Madrid Fault

Haiti Quakes Raise Questions about Reelfoot Lake and New Madrid Fault

aerial photo Reelfoot Lake, created by earthquakes in 1811-12 in Northwest
Tennessee and Southwest Kentucky. Photo: GoogleMaps

Story By: John Brannon Northwest Tennessee News Messenger Staff Reporter

Friday, February 5, 2010

Given the 7.0-magnitude earthquake that devastated Haiti on Jan. 12, should we be nervous about the New Madrid seismic zone?

“There’s no reason to be any more nervous than you were
yesterday,” said Dr. Mitch Withers, an associate research professor at
the Center for Earthquake Research at the University of Memphis. The
zone includes parts of southeastern Missouri, northeastern Arkansas,
West Tennessee, western Kentucky and southern Illinois. The fault
system crosses five state lines as well as the Mississippi River in at
least three places.

Also known as the Reel-foot Zone because large earthquakes in 1811-12 created Reelfoot Lake, it produces between 150 to 200 quakes a year. “Most are too small to be felt. By far, most are less than magnitude 2. It has to get up to 2.3 or 2.5 to be felt,”Withers said.

Seismologists — those who study earthquake activity — use
what is known as the Richter scale to measure ground-shaking intensity.
The scale ranges from 1 to 10. Thus, a 7-point quake such as the Haiti
quake is violent but much less so than an 8-point or 9-point quake.
Each full-point increase on the scale is 10 times greater. For example,
a 7-point quake is 10 times greater than a 6-point quake. Therefore,
the greater the intensity, upheaval and shaking, the greater the
prospects of widespread damage.

The earthquakes that hit the Mid-South in 1811-12 were centered near New Madrid, Mo., and are estimated to have been in the 8.0 range on the Richter scale. The New Madrid seismic zone has been characterized as the most active area in the United States east of the Rocky Mountains. In this day and time, a Richter-7 on the New Madrid zone would be destructive, Withers said, but not as destructive as the Richter-7 that hit Haiti.

Reelfoot Lake cyprus trees small.jpg

a look at Reelfoot Lake today...what earthquakes created
in 1811-12 is now a fisherman's paradise

“That’s because in this country there are building codes that are enforced,” he said. “I’m not sure if Haiti has building codes. If they do, why aren’t they widely enforced? We, in this area, don’t have the same (strict) building codes
that California does. So (in the event of a big quake) we’d be worse
off than California, but at least we have better building standards than they do in Haiti.”

Research scientist Seth Stein of Northwestern University has published articles asserting that the New Madrid seismic zone is shutting down.

“There is a consensus that he’s incorrect,” Withers said. “The USGS (United States Geologic Survey) had workshops to try to come up with (a rebuttal). Everyone else agreed that New Madrid remains one of the highest hazard areas in the eastern United States.” On the other hand, he said, the uncertainties are very large.

And according to the “best theories,” earthquakes shouldn’t happen here
at all. “But we know they have, at least three times. The last major
one was in 1811-12,” he said.

Meanwhile, what to do? “We just want to make sure, at least at the government level, that we are prepared for significant disasters, whether they be hurricanes or ice storms or floods or earthquakes,” he said. “On a personal level, we’ve said that people need to be prepared to be on their own without water and electrical power for three to five days. They need to have a survival
kit. Those are steps to take, whether it be earthquakes or floods,
that we, personally, and our government should be preparing for. We
don’t need Seth Stein to tell us we need to do nothing. We need to make
some decisions that we’re not going to be stuck like those poor souls
in Haiti.”

Withers is in charge of a network of 90 automated monitors —
listening posts — that record earthquake activity in an area from
Marked Tree, Ark., to southwestern Kentucky and the Missouri bootheel
and northwest Tennessee. The data is automatically fed into
supercomputers at the Center for Earthquake Research.

“Because we know so little (about earthquakes), we are trying to develop models that can tell what is going on in the New Madrid zone so that we can, with greater certainty, know what to expect,” he said. “So we have
instruments that record data from earthquakes we have several times a
week. So we learn something. The earthquakes that happen today will
teach us something about those that happen tomorrow. “We learn a little
more from every earthquake.”

According to the Missouri Department of Natural Resources:

• The New Madrid Seismic Zone appears to be about 30
years overdue for a magnitude 6.3 because the last quake of this size,
a magnitude 6.7, occurred 100 years ago at Charleston, Mo., on Oct. 31,
1898.
• A magnitude 7.6 earthquake in the zone would cause major damage
near the fault system in the Missouri Bootheel, northeast Arkansas and
western Kentucky and West Tennessee. Significant damage is expected to
extend north to St. Louis ... up the Ohio and Wabash River Valleys and
down the Mississippi to Greenville, Miss. Significant damage is also
expected in about 15 counties in southern Illinois, western Kentucky
and West Tennessee.