Today’s ‘quake’ a false alarm, but…

So today I get a text from my daughter. Which a year and a half ago would have been really big news because here at the Matile Manse, we did not text. But after the younger Matiles insisted, we figured out how to do it and then we bought iPhones for each other for Christmas last year. Which has made the process lots easier—no more punching thousands of buttons to text “How are you? I am fine.” In fact, we don’t need to punch ANY buttons at all since the brain that lives in our iPhones lets us talk to it to create emails and texts alike.

Anyway, I get this text asking if we felt the earthquake. To which I replied no, and by the way when did this happen. About 12:30 or thereabouts, she said. But no quake did we feel, and now it turns out it was probably some guys dynamiting in a quarry over east of us.

But it could have been an earthquake, since we live just about on top of the Sandwich Fault. Making the story more believable, there have been a couple other minor quakes here in the Midwest during the past few days.

One of these days, though, and it’s only a matter of time, we’re likely to feel the effects of The Big One. Really. Right here in God’s Country. Because it’s happened before.

What may have been the strongest earthquakes ever to hit North America struck along the mid-Mississippi River Valley during the winter of 1811–1812. Tremors from a succession of quakes pounded the area not once but three times. Fortunately, very few folks were living in what was then called the Illinois Territory, but even with so few residents (scattered Indian villages, widely scattered white settlements in the south, a few French traders at Peoria, and a few soldiers at Ft. Dearborn) deaths did occur.

A 19th Century artist’s depiction of the power released when the New Madrid Fault slipped in 1811, sowing chaos up and down the Mississippi Valley.

The first quake, measuring an estimated 8.5 on the old Richter Scale (now superseded by the Moment Magnitude Scale (MMS), on which it measured 8.2), struck about 2 a.m. Dec. 16, 1811. The second tremor rumbled through the area about six hours later, and measured the same 8.2 on the MMS. A third quake, with an MMS rating of 8.1, struck on Jan. 23, 1812. The most powerful of the three tremblers, estimated by some seismologists to have registered as high as 8.3 on the MMS, hit the by then well-shaken residents of the Mississippi Valley on Feb. 7. In comparison, the hugely destructive 1906 San Francisco Earthquake measured 7.7 on the logarithmic MMS scale, meaning the Illinois quake was about six times as powerful.

Future Illinois Gov. John Reynolds, a young man in his early 20s when the quake hit, said in his 1879 history of Illinois that the quake caused so much noise and shaking of the family’s log cabin that his father thought Indians were attacking.

The series of quakes was felt as far away as Washington, D.C. Richmond, Va. residents out walking when the quake struck found it difficult to stand as the shock passed.

The final and most powerful of the series of disturbances had its epicenter near New Madrid, Mo., then a small frontier hamlet, which was destroyed. A number of houses and other buildings were destroyed or damaged at St. Louis. The power of the uplift quake created temporary waterfalls on the Mississippi River, and changed the course of the river itself, creating the great looping Kentucky Bend. Temporary dams of fallen and uprooted trees and subsidence of sections of riverbank suddenly tumbling into the stream, along with the sudden uplift caused the great river to flow backwards for a period of minutes. One flatboat crew reported their craft was carried back upstream at a pace faster than a man could walk.

Artist Gary R. Lucy’s evocative portrait of the New Orleans, the first steamboat on the upper Mississippi, depicts a calmer voyage than that the boat completed during the winter of 1811 when its crew witnessed the great earthquake. See more of his wonderful work at http://www.garylucy.com/

As it happened, one of the very first steamboats on the Mississippi, the New Orleans, was steaming downstream when the quake hit, and the account by its crew, when they finally reached New Orleans after a harrowing voyage on a river that had suddenly become foreign to even the most experienced pilots, left a valuable eyewitness account.

In fact, boatmen up and down the river frantically tried to cope with the vast changes in the landscape that took place as they watched. No one knows how many of them perished during the series of quakes.

A request sent to Washington, D.C., dated January 13, 1814, by William Clark, he of Lewis and Clark fame and then the governor of Missouri Territory, asked for federal relief for the “inhabitants of New Madrid County.” Historians say this was quite possibly the first example of a request for disaster relief from the U.S. Federal government.

The central United States is far from any active volcanoes or any other of the more common guides to the possibility of earthquakes. So how did the 1811-1812 quakes happen, and could they happen again?

Eons ago, a failed rift in the plate on which North America rides became the Mississippi Valley, while cracks radiating from it became fault lines, the most active of which is the New Madrid Fault. It is that fault that slipped causing the great earthquake of 1811-12.

But there are those other faults as well, including one that diagonally splits Kendall County, running from Oswego (home of the Matile Manse) northwest to Ogle County. This dual fault, called the Sandwich Fault Zone by geologists, has been mostly dormant in historical times. A second fault system that cuts through nearby LaSalle County and extends southeast to the Wabash River—called the LaSalle Anticlinal Belt—is a bit more active. A September 1972 earthquake measuring 4.2 on the Richter Scale was related to the LaSalle Anticline.

Since Illinois and Missouri are in the middle of the North American tectonic plate, earthquakes here are not caused by our area colliding with another plate. Rather, quakes here are more due to stresses caused as the North American plate is thrust westward as new crustal material wells up out of the Mid-Atlantic Ridge. The gigantic stresses caused as the North American Plate is forced into the Pacific Plate sometimes cause the ancient faults along the Mississippi River to move, causing earthquakes.

So what would happen to us if another similar quake happened today? Well, we’d get shaken pretty well, and tall buildings in Chicago would sway and likely shed some structural panels. Here in Kendall County, damage would likely be minimal for buildings, including bridges, built on bedrock and in areas underlain by gravel. Homes and commercial buildings built on less stable soils, however, could be seriously damaged by “liquefaction,” as groundwater forced up through the soil momentarily liquefied it. For cities farther south, including St. Louis, Mo. and Springfield here in Illinois, the impact would be very serious indeed.

Today’s ‘quake’ proved to be a false alarm. But it’s been 202 years since the last Big One hit the Midwest. What has happened once could well happen again. And when it does, I suspect there won’t be a bit of doubt what has happened.

Advertisement