TBT: Shaken up

Earthquake Hazard Map from USGS
This year, Illinois celebrates its bicentennial of statehood. One part of the celebration is a review of 200 years of Illinois history. Of course, while statehood occurred 200 years ago, Illinois history extends long before that date. In fact, one important development in our state’s history which has substantial implications right up to today began thousands of years ago with the first rumblings from the New Madrid Seismic Zone.

Scientists have tried many different methods of studying the history of the New Madrid Seismic Zone, the source of a series of earthquakes along a fault line running from Illinois through Missouri, Tennessee and into Arkansas. They have found signs of significant earthquakes hundreds or even thousands of years ago. What is certain, however, is that just seven years before Illinois became a state, the New Madrid Fault was the source of three of the strongest earthquakes ever recorded in the United States. Something else that is widely believed among scientists is that the possibility still exists of another major earthquake in the same area.

In the pre-dawn chill of December 16, 1811, an earthquake about as strong as the one which would devastate San Francisco in 1906 struck the central Mississippi River valley. The quake was believed to have been centered in the northeastern part of present-day Arkansas, but its effects were felt over a wide area, radiating north into the Illinois Territory. Though the area was sparsely populated, some eyewitness accounts have survived, including one from a future Governor of Illinois.

Governor John Reynolds
John Reynolds, who would serve as governor from 1830 to 1834 wrote about the quake in his autobiography My Own Times, writing that “the whole valley of the Mississippi was violently agitated,” and noting that “the cattle came running home bellowing with fear, and all animals were terribly alarmed on the occasion. Our house cracked and quivered, so we were fearful it would fall to the ground.”

Reynolds’ account includes reports of chimneys collapsing in the “American Bottom” area around the territorial capital of Kaskaskia and church bells ringing farther north in Cahokia from the shaking. In all, the quake shook an area ten times larger than that affected by the shock that would hit San Francisco nearly a century later. And this was only the beginning.

Nearly six weeks later on January 23, 1812, there was another shock of almost equal strength, this one centered a little farther north in present-day Missouri. Two weeks after that, on February 7, the third and most powerful of the trio of quakes hammered the area, again centered in southeast Missouri near the settlement of New Madrid, which was completely destroyed. The series of quakes was felt as far away as Detroit and New Orleans, and caused damage in Cincinnati.

In Washington D.C., President James Madison wrote about the quake in a letter to his friend Thomas Jefferson. “The re-iteration of earthquakes continues the uproar from certain quarters,” the President wrote. “They have slightly reached the state of N.Y. and have been severely felt W. & S. Westwardly. There was one here this morning at 5 or 6 minutes after 4 o’C. It was rather stronger than any preceding one, & lasted several minutes, with sensible tho very slight repetitions throughout the succeeding hour.”

The aftershocks continued for years afterwards. Damage was so severe in the New Madrid area that in 1814 Missouri’s territorial governor requested help from Congress. It was approved the next year with a $50,000 appropriation for recovery. It is believed to be the nation’s first grant of federal disaster assistance.

As the decades went by and more people moved into the area, more earthquakes were detected and recorded. The first seismograph was installed in St. Louis in 1909 (today the five-state region between St. Louis and Memphis is home to around 270 of the machines). Records of the Illinois State Geological Survey indicate dozens of quakes in every part of Illinois, from the southern tip to counties on the Wisconsin border. They include five tremors of greater than 5.0 magnitude on the Richter scale. Some of these quakes were related to the New Madrid Fault and the New Madrid Seismic Zone. Others were on different faults that have been discovered over the years. Though Illinois has not experienced a major earthquake like the series that hit in 1811-1812, quakes have never been completely out of the picture for the Prairie State. However, if asked what kind of natural disaster most concerned them, many Illinoisans would likely have said something weather-related like tornadoes or winter storms. Certainly not earthquakes.

That changed in 1989.

In several newsletters and public speeches that year, a New Mexico climatologist made a prediction based on tidal patterns that a destructive New Madrid fault earthquake would strike on December 3, 1990. Though the prediction received little support from others in the scientific community, it garnered an enormous amount of publicity. That fall, the nation was transfixed by the images coming from San Francisco when a strong earthquake struck the city just minutes before a nationally-televised World Series baseball game. Suddenly, earthquakes were back in the spotlight, and parts of Illinois were right next to ground zero.

As the date of the predicted cataclysm approached, the world’s news media descended on southern Illinois and southeast Missouri. Families, schools, businesses and communities rushed to complete preparations for the big quake. A small quake which hit in late September added to the sense of unease. Newspapers printed lists of safety precautions and contents of emergency kits. State and local governments conducted earthquake drills, and students in those schools which were not closed on December 3 learned how to duck and cover under their desks in exercises reminiscent of the air raid drills of the 1950s. As the sun rose on December 3, 1990, an entire region of the country braced for disaster.

And then nothing happened.

A report compiled by the U.S. Geological Survey (USGS) after the fact found that “no earthquakes as large as magnitude 6 occurred anywhere on Earth during the interval November 25 – December 10, 1990.”

People in Illinois and neighboring states breathed a sigh of relief and went about their lives in the days after December 3, 1990. But the excitement over the unfulfilled prediction did have a silver lining: it reminded the public that the Midwest is not immune from earthquakes, and that there are sensible precautions to take. Many of the preparedness actions for earthquakes, such as having flashlights and batteries, canned food and bottled water and making a family communication plan, are also useful for other emergencies. This fall Illinoisans will join with the Federal Emergency Management Agency and the American Red Cross in the Great Central U.S. ShakeOut earthquake drill on October 18.

Today the USGS continues to monitor the New Madrid Seismic Zone and to issue warnings about its potential. What most distinguishes the danger today compared with that which existed in 1811 is the presence of millions of people in areas adjacent to the New Madrid Seismic Zone. Two hundred years ago, John Reynolds had about 12,000 Illinois neighbors. Today our population is in the neighborhood of 13 million.

According to the USGS the zone is the “most seismically active area of the United States east of the Rocky Mountains.” It has around 200 earthquakes every year, though most are small enough to escape much notice. “There is broad agreement in the scientific community that a continuing concern exists for a major destructive earthquake in the New Madrid seismic zone,” the USGS wrote during the bicentennial of the major quakes. “The preponderance of the evidence leads scientists to conclude that earthquakes can be expected in the future as frequently and as severely as in the past 4,500 years.”