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Earthquakes in the Eastern U.S.

    Just saw this story about the New Madrid fault, but have a bone to pick. The thrust of the story seems about right: The eastern United States has its own set of seismic hazards, not least of which is this rather mysterious fault that broke in 1811-1812 in a series of quakes that have been estimated as high as magnitude 8.1. New England and South Carolina have had major quakes in the past; in fact many of the major cities of America with no cultural memory of earthquakes (say, New York City) could be vulnerable to an earthquake. But -- a big but -- we tend when we write about these things to claim more knowledge than we actually possess. Take that 8.1 magnitude figure for the largest New Madrid quake in the 1811-1812 series. What is that based on? Did anyone have a seismometer then? I don't think the word "seismometer" existed. People didn't even know the world was old at that point. I believe the figure is based on the accounts of survivors. Basically they talked about chimneys falling down and landslides and so on, and scientists would then say: Let's call that an 8. You have to wonder if it's not roughly as scientific a process as the judging of figure skating. Recently the very smart seismologist/historian Susan Hough mentioned an interesting fact about New Madrid: Most people back then lived right along the rivers, on soft ground that is prone to liquefaction and increased shaking during a quake. Maybe their 8 was just a 6 back in the hills.

By Joel Achenbach  |  June 23, 2005; 7:42 AM ET
 
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Comments

Usually it's the other way, isn't it?

An 8 in the hills may only be a 6 in the Big City...?

There have been some tremors along the Balt Wash corridor recently, including one earlier this year. Not to foment fear or anything, but the point about the Eastern US being unprepared for a quake, with at least some chance of one actually occurring seems valid.

My personal preparation consists of assuming a wider stance (feet the same width apart as my shoulders), and always wearing rubber soled shoes.

bc

Posted by: bc | June 23, 2005 9:25 AM | Report abuse

I think you get the 8 on the Richter scale from the reports of the quake. I grew up in a town along the Indiana-Kentucky border where the quake caused the Ohio River to run backwards and shift its channel. The result is that part of Kentucky is now on the other side of the Ohio River from the rest of the state. The River is border for the rest of the state except in this area.

Posted by: TP | June 23, 2005 9:33 AM | Report abuse

These were pretty big quakes felt over the most of the Eastern and Mid-West US. Recent studies have identified that the many of the surficial sands in the river valleys are the "most extensive liquefaction soil deposits in the world." The astonishing thing was three earthquakes of this large magnitude at once. The damage that a similar set of events would cause today would be virtually incalculable.

The old construction in the US predating the 1960s when earthquake engineering began to be understood means that many communities along and east of the Mississippi are suceptible to substantial damage.

The only reason it doesn't show up as the same level of risk as California and Alaska is because the earthquake frequency is much lower. The "big one" comes hundreds of years apart in the east along each major fault instead of only 100 years or so in California and there are fewer faults. The last major quake east of the Rockies was 1886 in Charleston. Most other faults have already gone at least 200 years without a major quake, so don't be surprised if something pops in the next few decades.

Posted by: rdd | June 23, 2005 9:40 AM | Report abuse

I don't know anything about earthquakes.
But we use to construct barometers out of a milk carton.

Posted by: fdg31 | June 23, 2005 10:32 AM | Report abuse

I suspect that the geological stratigraphic record contains evidence of how far the land on either side of the fault moved; this would provide basis for an estimate. Also, I have read that the earthquake rang bells in Philadelphia. From that, it shouldn't be too hard to extrapolate the force of the earthquake at its epicenter.

Posted by: greinerb | June 23, 2005 10:55 AM | Report abuse

Apparently science has done its bit to verify what most of the posts have said -- see http://www.eas.slu.edu/Earthquake_Center/SEISMICITY/Street/rstreet.html for an example, with data indicating the different degrees of damage.

As a Missouri resident, I just keep the earthquake endorsement on my homeowner's insurance up to date.

Posted by: KC Teacher | June 23, 2005 1:06 PM | Report abuse

Brilliant observation, Joel! This kudo comes from a survivor of several snowstorms in Georgia.

Posted by: InvestiGator | June 23, 2005 11:33 PM | Report abuse

Good point on insurance... and the Ohio river. No wonder the TVA is constantly monitoring their dams and power plants... nothin' works better than a mud dam in a huge earthquake.

Posted by: Dolphin Michael | June 24, 2005 8:09 AM | Report abuse

this story reminds me of an old song:

"There's an old man with conviction/
Although he's getting old/
Mr. Browning has a prediction/
We've all been told."

Posted by: BellevilleBlues | June 24, 2005 4:01 PM | Report abuse

I thought I read long ago that most of the buildings in Memphis and St. Louis have not been built to be earthquake-proof, so it won't take a very big one in New Madrid to cause a lot of damage.

If you think that is scary, think of the volcano under Yellowstone, which is huge. It was due to blow 30,000 years ago, and if it does, the ash will cover much of the midwest, maybe all the way to New Madrid. Read "A Short History of Nearly Everything," by Bill Bryson.

Geology happens, and legislation can't fix it. And to think, in college people made fun of that class as "rocks for jocks."

More info on all of the many earthquakes happening in the world today, now, as you read this:

http://neic.usgs.gov/neis/bulletin/

Posted by: Sigh | June 25, 2005 12:07 AM | Report abuse

there are plenty of more or less objective measures of earthquake intensity: landfall,along faultlines, length thereof, etc...
heresay has it's say and is heard, but not to the detriment of physical sciece (for the most part)....

Posted by: device | June 27, 2005 2:44 PM | Report abuse

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