Midwest/Ozarks may be hit by 8.0+ Earthquakes in the future

Following yesterdays' quake in Souther Missouri/northern Arkansas, Live Science ran this article about seismic activity near the New Madrid fault line:

www.livescience.com...


It points out that tremendous quakes have been released in the seemingly stable area in the past... quakes that have been felt as far away as Boston.

"The infamous series of three New Madrid quakes in 1811-1812 occurred a few weeks apart, from Dec. 16 to Feb. 7. They measured 8.1, 8.0 and 7.8 and represent three of the four strongest earthquakes ever recorded in the lower 48.
"Strong earthquakes in the New Madrid seismic zone are certain to occur in the future," states a USGS fact sheet.

"The strongest of the New Madrid events was 10 times more intense than the 1906 San Francisco earthquake, scientists say. Earthquakes of similar intensity occurred around the year 900 and again in the middle 1400s along the New Madrid fault, named for a small town in Missouri."

I have relatives in N Arkansas and have travelled through this region hundreds of times. N. Arkansas and S. Missouri are extremely hilly while the region that borders the Missippi river is often flat. I have no idea how the hilliness affects the spread of the energy released by an earthquake... but I imagine that some damage would be absorbed by major cities like Nashville (in TN) and St. Louis if another 8 pointer hit again.

The soft clay-like composition of the ground in the Miss. Valley region allows seismic energy to spread out a very long way. Similar quakes in California would not effect nearly the same area. That's why the Madrid fault is such a worry: It sleeps most of the time, but when it wakes up, a lot of people will know it.

The Arkansas/Missouri area is very cavernous. Just riddled with them. I can't get straight in my head whether that might be a good thing or a bad thing.

To me, it seems they could act as baffles - if you'll allow - and could actually diminish potential damage in a given quake. But I might be completely wrong on that. **

I know I've heard for years that there are lots and lots of tiny quakes happening in Arkansas on a daily basis, but the 4.1 yesterday was a surprise!

Val
I think you're right in that the caves would act as a baffle, because the shock waves don't travel well through the empty spaces..however..couldn't a collapse of one of these caverns actually be a big problem in and of itself? Without knowing the dimensions or placement though it's impossible to say whether or not population centers will be affected.

I imagine the consequences could be severe if a sinkhole-like event were to take place, and set of a chain reaction of similar collapses. A trench could appear through several states if the caverns are interconnected, which I suspect they are.

Interesting things to ponder to be sure.

Originally posted by WyrdeOne
Val
I think you're right in that the caves would act as a baffle, because the shock waves don't travel well through the empty spaces..however..couldn't a collapse of one of these caverns actually be a big problem in and of itself? Without knowing the dimensions or placement though it's impossible to say whether or not population centers will be affected.

Interesting things to ponder to be sure.

Mammoth Cavern sits directly under Branson, Missouri.

Originally posted by Valhall

Mammoth Cavern sits directly under Branson, Missouri.

And that would be a bad thing???


Seriously, the worst damage would be in areas subject to liquefaction. This would include areas of St Louis, Chicago, and probably Memphis.

Interesting. It makes me glad I live on a giant granite mountain. This whole "Holes opening up in the earth" business is for the birds. It appears the local talking heads are brushing it off. I wonder if they were told to do so, or if they're chalking it up to normal activity despite the above average reading. I can't wait for armageddon, because I know some weather man is going to be on the television, smiling like a retarded golden retreiver, saying something like "Well Bill, it's a little warm out there today. There's a warm front moving over the lower midwest and we're seeing some isolated areas of fire falling from the sky. Visibility is low, so take care out on those roadways on your way to work. Here's Stacey with traffic."

Seriously, they hire people who have no idea what they're talking about it seems, because they deliver news of anomalies in the same cadence with the same plastic smile. I was watching the weather channel online a few days ago during the snowstorm in Texas, and the weather lady just smiled and pointed and went on like usual, putting no emphasis whatsoever on any of the oddities she was reporting. It was highly unusual to see and hear someone being so calm and seemingly unaware of the very news she was reporting.

No one's really sure what's up with the New Madrid fault system -- or even what causes the earthquakes -- because there aren't any subducting plates within a thousand miles or so.

But I doubt if caverns would ameliorate any earthquake, they're pretty near the surface compared to the origins of most earthquakes (~30 km down).

But after the 1811/1812 earthquakes, the Mississippi actually ran backwards for several hours; and, a large portion of a cliff on one side of the river collapese into the river. At the time it was unpopulated -- now it's the city of Memphis.

By the way, the locals pronounce the name of the town "MA-drid", not "muh-DRID".

[edit on 11-2-2005 by Off_The_Street]

where i live in arkansas, there are caves everywhere. i don't think that is good, especially in populated areas. i can imagine sink holes opening up everywhere around me

Actually, if you are in limestone country, you are probably ok. The water table is low, and the bedrock is close to the surface. It is the areas that are built up on silt outwash basins, either glacial outwash or river deposits. In a quake that stuff turns into quicksand.

liquefaction

Originally posted by Valhall

Originally posted by WyrdeOne
Val
I think you're right in that the caves would act as a baffle, because the shock waves don't travel well through the empty spaces..however..couldn't a collapse of one of these caverns actually be a big problem in and of itself? Without knowing the dimensions or placement though it's impossible to say whether or not population centers will be affected.

Interesting things to ponder to be sure.

Mammoth Cavern sits directly under Branson, Missouri.

I've been to the Mammoth caverns and the Blanchard Springs cavern in that area. Both are impressive.... though I have to say that I like Blanchard more. One of the things the guides show you there is the skeleton (still meshed with the 'living' rock) of a Native American boy who died in the cave centuries ago. It's pretty creepy because -- based on the natural openings that would have been around back then -- he was separated by several miles from the surface. Just thinking about what he went through near the end is enough to give you a chill.

I seriously doubt that the caves would "cave in" if you think about it, with the way they are shaped inside a cave would probably be the safest place to be. I believe that the Native American kid died in there because that is where they lived. What worries me is the amount of natural springs running underground everywhere. with everything being so darn soggy and the fact that we have already seen a few mudslides this winter because of the rain. Sink holes are far from unheard of. If it goes, especially this year with it being so wet, we are in deep doodoo.

reply to post by WyrdeOne

I agree, that the powers that be don't give potential or ongoing catastrophes the
seriousness and respect they deserve, giving many the impression that all is
well. But think about the reverse of that, having everyone thing the big one
is right around the corner would send some into panic and send property
values into a nosedive. Until seismic analysis displays greater accuracy,
it is hard to say what will happen even with an earthquake swarm. The
"big one" could be tomorrow or it could be 500 years from now. Good
point regarding the caverns though. Perhaps during prolonged seismic
activity like the past week, they should put out a sign for visitors saying
enter at your own risk and the reason why.

i just came across this from reuters

"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)"