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Posts Tagged ‘New Madrid Seismic Zone’

The other night we watched yet another of those “disasters of the Apocalypse” shows that seem to pop up with almost absurd frequency these days.  It’s usually the Discovery Channel, or the History Channel, or the Learning Channel, but they’re on all the time.  I suppose it has something to do with the ominous approach of 2012, the year the Mayan calendar ends and a bunch of people believe “the big one” is going to go up.

Didn’t the Mayans live a thousand years ago?  Their calendar probably ended in 2012 simply because they found more entertaining ways to occupy their time.  Hopefully the weight that lots of people give to this nonsense is mostly just a figment of my imagination, because if it’s not, then there are a lot of people that haven’t (unlike the Mayans) found more entertaining ways to occupy their time.

But I digress.  Anyways, this show was one we hadn’t seen before and was narrated by Samuel Jackson.  It was sort of a countdown of the various ways lots of people could get killed by disasters.  There was a big rainstorm over California at Number 5.  Number 4 I can’t remember, but I’m sure it was worse than a container of duck toys spilling into the Pacific.  Numbers 2 and 1 were completely predictable.  Two was a massive tsunami caused by a volcanic eruption and landslide at La Palma island in the Azores…this has been described on a dozen different “what-if” shows.  And of course, Numero Uno was the mega-volcano erupting in Yellowstone, which would lay waste to most of the American existance.  Again, we are not surprised, as this potential disaster is also well-known.

It was Number 3 that most caught my attention…an earthquake.  To be more specific, an earthquake in the Midwest.  Earthquakes in this area aren’t nearly as famous as those occurring around the Pacific Rim and the corresponding Ring of Fire, because they’re so rare.  But when the bigger ones hit, they pack a powerful wallop.

The most famous of the “Midwest” quakes on record was a series of temblors that culminated in a tremendous quake in February of 1812.  Centered over southeast Missouri, northeast Arkansas, and western Tennessee, the biggest ones were felt over a 1,000,000 square miles and damage was recorded as far away as Maine.

But it all began 200 years ago today…December 16, 1811.

At 2:15 in the morning, people along the New Madrid Fault were thrown from their beds by a tremendous rumbling.  They scrambled out of their crumbling homes and got a night-time view of the apocalypse, as the landscape heaved and bucked like a drunken man, under the influence of a quake that would have registered close to 8.0 on the Richter Scale.  There were sand blows and landslides, soil liquifaction and, to hear the locals tell it, a brief reversal of the mighty Mississippi River.

Six hours later, another quake similar in scope struck the region again.  Too large to be an aftershock, it classifies as its own separate quake.  People all over the region were terrified, looking heaven-ward and awaiting the arrival of the Four Horsemen.  Damage was extensive, but deaths relatively light because the population was sparse.

For many years, scientists believed that major earthquakes struck along the New Madrid Fault every couple of hundred years.  And guess what?…we’re at exactly 200 years today.  But seismic activity along the fault has dwindled to a relative handful of very small shakers each year.  I read somewhere that geologists think the fault might be seizing up to a point where quakes no longer occur.

But for the millions of residents that live in St. Louis, Kansas City, Memphis, Chicago, and other large cities in the region, there is that small concern.  I live in central Iowa, several hundred miles from the fault, but I think about it all the time.  Homes in the Midwest are built with tornadoes (and in recent years, flooding) in mind, not earthquakes.

A repeat of the quakes that began two centuries ago would be cataclysmic.

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The earthquake that rocked Alaska on March 27, 1964 needs no special introduction.  It is the most powerful earthquake recorded in the Northern Hemisphere.  Only two others, the great Chilean earthquake of 1960 and the 2004 quake off Sumatra (which caused that terrible tsunami), have approached or surpassed the Alaskan quake’s strength, which struck in the Prince William Sound area shortly after 5:30pm on Good Friday.

Geologists believe that earthquakes occuring along subduction zones tend to be more powerful than quakes along standard fault lines, because greater stresses build up as the upper plate passes over the lower.  The Alaskan quake was of that type and, while I wasn’t alive when it happened, the pictures show tremendous damage.

The land buckled and heaved during the 4-minute quake, permanently rising as much as 30′ (the Kodiak area) in places while dropping 10′ in others, creating new beachlines and opening fissures in the surface.  In the photo above, you can see how the beach areas of Middleton Island on the left slid nearly 12′ from its original level on the right.

Of course, the forces we are discussing here were astronomically stronger than any man-made structures.  Anchorage was heavily damaged, as were a good number of smaller cities and towns.  In fact, significant damage was reported over an area covering more than 50,000 square miles from a quake that was felt over more than half-a-million square miles.  Thousands of major aftershocks over the next 18 months served to terrorize an already stunned populace trying to put their lives, homes, and infrastructure back together.  But its effects were even more far-reaching.

The rapid shift along the plates triggered tsunamis that were detected throughout the Pacific Ocean and caused widespread damage.  While deaths from the quake itself (falling buildings, etc.) were incredibly few (10-15, depending on your source), 120 fatalities were caused by tsunamis.  Crescent City, on California’s northern coast, was particularly hard hit, where 14-foot waves were responsible for 11 deaths and millions of dollars of damage.

But the location of the Alaskan earthquake (well off the equator in the upper Northern Hemisphere) also caused the planet to wiggle, which means that the effects of the quake were seen worldwide.  Small tsumani waves were detected in Cuba, small boats were reportedly capsized off Louisiana’s coasts, and water oscillations were seen in Africa.

Here in the central United States, we occasionally mention the fabled “big one” that supposedly will someday strike the San Andreas Fault and knock the most heavily-populated parts of California into the Pacific, while simultaneously casting a wary glance in the direction of the New Madrid Fault, knowing we stand on shaky ground ourselves.  But I think a good number of us would like to believe that “the big one” has already come and gone, striking the Alaskan coast 46 years ago (as of this writing).

Time will tell if that belief stands up to the motion of the tectonic plates.

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When we think of earthquakes, we tend to think of specific places like San Francisco or Alaska, where major quakes have occurred.  We probably also think of places like Indonesia and Bande Aceh, where an underwater earthquake and subsequent landslide caused the immense tsunami on December 26, 2004.  Others of us may think in more general terms, like the Ring of Fire, the large volcanic and seismic zone ringing the Pacific Ocean that has spawned much of the activity in the places I just mentioned.

But rarely do we think of the central United States when discussing topics related to seismology.  And that’s easily understandable, because earthquakes in Mississippi River Valley just don’t happen all that often.  But when they do,…

It’s a relatively unknown geological fact that, as the longest river in the United States flows past southern Missouri, Tennessee, and Arkansas, it passes over a sizeable fault line.  Known as the New Madrid Seismic Zone, it encompasses the aforementioned states (as they border on the Mississippi River) as well as southern Illinois, western Kentucky, and even the northern tip of Mississippi.  And in this area there have thousands of minor temblors and quakes in recent years, though no major quakes.

For those, we need to go back to the winter of 1811-12, when major quakes were recorded, quakes that rank as some of the most powerful in U.S. history.  Beginning in December of 1811, two major quakes were followed by numerous smaller shakes and aftershocks.  But all of those were the lead-up to the biggest of the quakes, which rocked the Midwest on February 7, 1812.  Centered around New Madrid, Missouri, estimates have the quake at 8.0 on the Richter Scale, and it was felt on a massive scale.

How massive?  Stories are told that the quake cracked sidewalks in the nation’s capital and knocked down chimneys in…are you ready?…Maine.  All told, the quake was felt in an area that covers 1,000,000 square miles.  By comparison, the infamous 1906 San Francisco Earthquake covered only about 6,000 square miles.  Though the scale was partially due to the bedrock in which the quake occurred, this was still a tremendously powerful quake.

Today, the fault is still active, and there is growing concern that another major shake-up is building, particularly since we are now approaching 200 years since the quakes of 1812.  What’s more, there has been very little earthquake preparation in the Midwest, and nothing at all approaching the scale of more earthquake-prone areas.  A repeat of the 1812 events would be catastrophic, considering the major population centers that could be affected.

Recommended Reading: When the Mississippi Ran Backwards: Empire, Intrigue, Murder, and the New Madrid Earthquakes – History, intrigue, and mayhem in one volume.  I’ve yet to read this book, but from what I’ve seen, it’s going to be part of my next book order.

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