The U.S.'s little known but dangerous seismic fault

[senorpepr]

Seismic activity in country's center sparks debate
After California quakes, attention turns to New Madrid zone

ATLANTA, Georgia (CNN) -- Earthquakes on the West Coast have prompted fresh speculation about "the big one" -- a quake that could dump a huge section of California into the sea.

A few have been large enough to shake the faith of skeptics -- a magnitude 7.2 quake on June 15, followed two days later by a magnitude 6.7, both off the coast near the California-Oregon border.

Doomsayers have warned about the Pacific Coast for years. But only a few have raised concerns about an area with the potential to be more dangerous than California -- the New Madrid seismic zone in the center of the country.


http://www.cnn.com/2005/TECH/science/06 ... index.html
It's a 120-mile-long system of three to five faults stretching from 40 miles northwest of Memphis to southern Illinois, near Cairo.

"The system is capable of producing a quake near 4.0 magnitude every three years," said Gary Patterson, a geologist and information services director for the Center for Earthquake and Research Information in Memphis, Tennessee. "And they'll cause minimal damage."

But New Madrid already has spawned four earthquakes this year of similar size, along with nearly 100 smaller quakes. Patterson said such activity may or may not be the precursor to a much larger quake.

The recent activity is an anomaly, he said.

"It's unusual, and we don't have any reason to believe there is increased risk," Patterson said. "But any time you have this kind of activity in an area that has a 25 [percent] to 40 percent chance of a 6.0 or greater in the next 50 years, it will draw attention."

And the region is ill-prepared for a strong quake, he added.
Under pressure

Scientists know little about how the New Madrid seismic zone works, but in the early 19th century, it was the source of the most violent series of earthquakes known in North American history.

The zone, named for the town of New Madrid, Missouri, is hundreds of miles from a tectonic plate boundary, which Patterson said defies the logic of coastal earthquake science.

"Plate tectonic theory can account for large quakes on the edges of plate boundaries, but plate boundary theory assumes a rigid continental plate," he said. "Madrid is in the middle of a continental plate, not on the boundaries."

Three large quakes happened in the winter of 1811-1812, and strong rumbles hit several times until near the end of the 19th century.

These quakes were felt keenly over more than 2 million square miles -- people in Boston, Massachusetts, felt one or more of the three main quakes, the first of which struck in three shocks on the morning of December 16, 1811.

Two more large shocks struck the area -- on January 23, 1812, and the largest and most devastating of all hit February 7, 1812, destroying the town of New Madrid.

By contrast, the 1906 earthquake in San Francisco, California, was felt over 60,000 square miles.

Patterson said the incredible distance the quakes reached was largely due to the cold, solid rocks "that make this continent float," a different environment from the plate boundaries on the coast.

"On the boundaries, the rock is hot, molten and broken up," he said. The solid rock carries the movement farther from the epicenter.

Earthquake researcher Otto Nuttli estimated 200 moderate to large earthquakes on the New Madrid fault between December 16, 1811, and March 15, 1812, and about 1,800 earthquakes of slightly lesser strength.

The stronger quakes lifted parts of the land high or dropped them down, and drew the Mississippi's waters in and threw them back far over the river banks. In some areas, the upheaval beneath the surface was so violent that it caused the mighty river to flow backward.

Whole islands in the river -- and entire towns -- disappeared.

The strongest quake in the area since 1895 was a magnitude 5.5 in 1968. New Madrid is "a sleeping giant we don't understand very well," Patterson said.

"But we realize the need to understand is very important," he added. "It's a challenge. If we understand this question, then we've really put in a piece of how the Earth works as a system."
Trouble for Memphis, other cities?

Patterson said he saw no reason for a "high level of concern" at the moment but added that so little is known about New Madrid that it's even more unpredictable than its coastal cousins.

The area isn't prepared for an earthquake of magnitude 6 or higher, specialists said. Damage from such quakes would be significant over a multistate area, Patterson said, with the likelihood of significant infrastructure disruption and damage to population centers and municipalities that would have huge economic impact.

Memphis, and to a slightly lesser degree, St. Louis, Missouri, could be seriously hurt by a strong quake, "especially when you have old infrastructure and a lot of buildings that predate 1940, when unreinforced masonry was a typical style," Patterson said.

"Our building inventory is very vulnerable and has not been shaken significantly," he said. "It's potentially a large disaster even from a magnitude 6."

Ted Ilsley, manager of the plan review section of Shelby County, Tennessee's building code enforcement division, said the building code is adequate for an earthquake the size of the 1811-1812 ones. This code has been in effect since 1989 in the county where Memphis is located.

The county is preparing to adopt an amended version of the International Building Code, a requirement to receive funding from the U.S. Department of Homeland Security.

The city of Memphis also likely will adopt something similar to Shelby County. Calls to the city's code enforcement division were not returned.

Although strong earthquakes strike the West Coast more frequently, New Madrid is "an active seismic zone," Patterson said, and population centers in the area should be concerned -- not with the frequency -- but with the consequences if one does strike.

"It does not take the big one to do a lot of damage," he said. "The most damaging quake in the United States, in 1994 [the Northridge quake in Southern California], causing $30 billion, some say $40 billion in damage, was a 6.7 in a place that's prepared generally for earthquakes."

There's no doubt that the New Madrid seismic zone has the potential to spawn catastrophic earthquakes. The question, as with most fault areas, is when it will occur.

Whenever it occurs, the quake likely will be felt far from its epicenter. The one in 1968, centered in southeastern Illinois near the confluence of the Tennessee and Ohio rivers, caused moderate damage, but it was felt across 23 states -- as far as the Carolinas -- and into Canada.

[HurryKane]

A buddy of mine just north of Memphis felt the one of those New Madrid quakes this year (maybe the strongest one?). He said it felt like a semi going by a couple of feet from the office. I'd read long ago that one of those big New Madrid quakes actually rang the Liberty Bell in Philadelphia.

I was amused/surprised to see a 2.2 mapped by the USGS to have occurred in the past week about 30-40 miles west of Tuscaloosa, Alabama, or about 70 miles from my hometown.

Freaky deaky. Here's another interesting article about the New Madrid that mentions the Liberty Bell folklore: http://www.aapg.org/explorer/1999/07jul/earthquake.cfm

[Brent]

A 7.0 on the New Madrid fault would be MUCH more severe than a 7.0 in California because the shock would carry farther. With less mountains in the east, people in MS/AL/GA and the Carolinas as well as Wisconsin/Michigan/Ohio/PA and parts of the Mid-Atlantic could have structual damage. Buildings are not up to standards like in earthquake prone areas.

Yes... there have been several small quakes in Alabama over the years. The biggest in recent memory was a 4.6 in Northeast Alabama in 2003 that was felt through most of the Southeast.

[Miss Mary]

This is just what I want to hear! I am 2 months away from sending my oldest daughter away to college down there - to Western Kentucky University (Bowling Green KY). Yikes! As we toured the campus we saw many Tornado Shelter signs in place. All over campus. At least 20 I counted. If they take tornado's this seriously, I'm sure there's a plan in place for earthquakes too.

Thanks for the article. I'm sure if I suggest to her what to do in a possible earthquake, I'll get that typical rolled eye look back. Now I have concrete articles to tell her about.

Mary

[pojo]

Yes, are standards up here are not to EQ standards by far. It seems like contractors around here think that any EQ activity is beyond us ... only happening in California. I do understand the New Madrid fault (I'm an Earth Scientist). If, and when, the 'big one' would happen on the New Madrid fault damage would most definity occur all along the Mississippi valley out probably from the Appalachians to the Rockies. That is a huge arena.

Anyways, one must also consider that Yellowstone is a 'sitting duck' Yes, Old Faithful erupts, but many do not know where the force of the eruptions occur from.... Yellowstone is sitting on a baccolith... a carved out underground mountain of volcanic sediments (ie Magma).... when this happens, the entire plains will most likely be affected.

[Brent]

This is just what I want to hear! I am 2 months away from sending my oldest daughter away to college down there - to Western Kentucky University (Bowling Green KY). Yikes! As we toured the campus we saw many Tornado Shelter signs in place. All over campus. At least 20 I counted. If they take tornado's this seriously, I'm sure there's a plan in place for earthquakes too.

Thanks for the article. I'm sure if I suggest to her what to do in a possible earthquake, I'll get that typical rolled eye look back. Now I have concrete articles to tell her about.

Mary

That's the problem... the last time a really major quake hit the area was in 1812, almost 200 years ago. No one alive today witnessed it. Back then, not near as many people lived in the areas devastated back then. The buildings are not built for earthquakes meaning they will collapse a lot easier and people aren't prepared. I'd be shocked if very many places have a "plan" because the mindset of a lot of people is "It only happens in California".

[Brent]

Anyways, one must also consider that Yellowstone is a 'sitting duck' Yes, Old Faithful erupts, but many do not know where the force of the eruptions occur from.... Yellowstone is sitting on a baccolith... a carved out underground mountain of volcanic sediments (ie Magma).... when this happens, the entire plains will most likely be affected.

If it's like the one 640,000 years ago well it's been nice knowing all of you. The magma would get most of the U.S. and the rest of the world would slowly freeze to death as the planet goes into a new ice age.

Have a nice day.

[Kelarie]

Anyways, one must also consider that Yellowstone is a 'sitting duck' Yes, Old Faithful erupts, but many do not know where the force of the eruptions occur from.... Yellowstone is sitting on a baccolith... a carved out underground mountain of volcanic sediments (ie Magma).... when this happens, the entire plains will most likely be affected.

If it's like the one 640,000 years ago well it's been nice knowing all of you. The magma would get most of the U.S. and the rest of the world would slowly freeze to death as the planet goes into a new ice age.

Have a nice day.

There is no way to tell the strength of the eruption at Yellowstone. If it is relatively minor, then I don't believe the entire world would hit a new ice age. Although, the worlds temperature would be affected by a few degree cooler. As it is, the planet is slowing transitioning into a "cold" house world. This will take time to fully transition. Of course one would never think of that would they?

[Brent]

Anyways, one must also consider that Yellowstone is a 'sitting duck' Yes, Old Faithful erupts, but many do not know where the force of the eruptions occur from.... Yellowstone is sitting on a baccolith... a carved out underground mountain of volcanic sediments (ie Magma).... when this happens, the entire plains will most likely be affected.

If it's like the one 640,000 years ago well it's been nice knowing all of you. The magma would get most of the U.S. and the rest of the world would slowly freeze to death as the planet goes into a new ice age.

Have a nice day.

There is no way to tell the strength of the eruption at Yellowstone. If it is relatively minor, then I don't believe the entire world would hit a new ice age. Although, the worlds temperature would be affected by a few degree cooler. As it is, the planet is slowing transitioning into a "cold" house world. This will take time to fully transition. Of course one would never think of that would they?

I understand... I said IF it was like the one 640,000 years ago.

[CentralFlGal]

Yellowstone could put an end to "global warming".

[feederband]

Yellowstone could put an end to "global warming".

Probably the end of everything as we know it