The New Madrid Fault Zone

The New Madrid Fault Zone

History
The largest earthquake sequence the United States has ever experienced happened east of the Rocky Mountains starting out in Northeast Arkansas on December 16, 1811. On the Richter scale, it was ~7.7 and five hours later AK experienced an aftershock of a magnitude of ~7.0. A little over a month later on January 23, 1812 New Madrid, MO experienced an earthquake with a magnitude of ~7.5, and again on February 7, 1812 reaching a magnitude of ~7.7. By March 15, 1812 approximately 2000 aftershocks had been felt. Damage from the largest of these shocks was reported from 300 miles away. In an effort to recover, then Missouri Governor, William Clark, ask for Federal relief for the inhabitants of New Madrid County. 1815 marked the first ever disaster relief act in the United States with Congress awarding $50,000. Earthquakes recorded after 1811-12 happened on January 4, 1843 with a magnitude of ~6.0 near Marked Tree Arkansas and again on October 31, 1895 with a magnitude of ~6.3 to 6.6 near Charleston Missouri, (USGS).
New Madrid, MO was founded in 1789 with about 400 hundred residents and the 1811, 1812 earthquakes were named after New Madrid as this was the only place with a sizeable population at the time. The New Madrid Fault System extends approximately 150 miles southward crossing five state lines. West coast fault zones are called transform faults in contrast, the New Madrid fault is called an intraplate zone. This means that there is a weak spot in the middle of the North American Plate with a series of faults in the Earth’s crust and is called the Reelfoot Rift, named after Reelfoot Lake in Tennessee, that was formed during the quake, (The Encyclopedia of Arkansas History & Culture).
It wasn’t until 1909 that seismographs were available, so in the 1800s, reports came from survivors. Witnesses reporting the ground moved like a wave indicating that the quakes ranged between 6.5 and 8. Comparing the Mercalli Scale, (invented in 1902 by Guiseppe Mercalli), based on observation to the Richter scale, (invented in 1935 by Charles Richter), based on actual magnitude is very similar. During a 7.5 magnitude few structures remain standing; bridges are destroyed, fissures in ground, pipes are broken, there are landslides, and rails become bent. A magnitude of 8.0 a person can witness waves on the ground surface, lines of sight and level distorted, and objects can be seen thrown up in the air, (Missouri, DNR).
Early Research
In the late 1970s, using oil-exploration equipment, seismologists bounced sound waves off the subterranean rock where the tremors were centered. It was discovered that along a large crack interlocking layers of rock were offset vertically and in some places as much as 3,300 feet. The theory was that sometime in the past the rock was uplifted, possibly by volcanism. As the volcanic flow cooled, part of the rock collapsed, creating sharp breaks. During magnetic and gravitational surveys, the underground rift was discovered along the fault zone. Scientists measured this rift to be at least 120 miles long, and 30 miles wide. They also believe this rift was created millions of years ago when the North American plate began to pull apart and molten rock rose to the surface. The rift halted and a weak area remains, (Time, 1979).

Geography
To further explain this weak area, tectonic forces stretched North America in Precambrian time. As the continent pulled apart, rock fractured to create two huge fault zones. The fault zones failed to develop into a divergent plate boundary, in result, weaknesses remain in the lithosphere. New Madrid lies at the intersection of these major faults. As the North American Plate glides over the asthenosphere, it may pass over irregularities, or bumps, in that plastic zone, causing slippage and earthquakes along these faults. Along with the 1811 and 1812 Madrid quakes, there has been evidence of quakes occurring in 1600, 1300, and 900. In 2005 researchers reported that additional earthquakes are likely to happen in the future due to rocks adjacent to the New Madrid fault are currently deforming about as fast as rocks adjacent to active tectonic plate boundaries, (Thompson, Turk, pp. 166-67).
The New Madrid Seismic Zone is not easy to study as the faults are hidden beneath 100 to 200 feet of thick layers of soft river deposited soils called alluvium. The continuation of soft new sediments depositing on top of old sediments, creates the faults to become hidden and therefore evidence of earthquake fault lines become buried. On the west coast, faults are either at or near the surface making them easy to be measured and analyzed, (DNR, Missouri).
Believe it or not, soil type can have a large effect on ground shaking and damage during an earthquake. Soft thick sediments increase seismic shaking. Below the Mississippi River Valley lies approximately 30 meters of soft sediment, resulting in intense ground shaking and land deformation during the New Madrid earthquakes of 1811 and 1812. The earthquakes were so strong that sand was blown up to the surface, called liquefaction. When sediments are sandy and water-filled, sediments can lose strength during earthquake shaking. Over pressured fluids can erupt to the surface known as sand blows. The earthquakes of 1811 and 1812 created one of the world’s largest sand blow fields along the Mississippi River Valley, and are still evident today. Geologists and Archeologists use ancient Native American artifacts buried in the upper Mississippi River Valley found in these liquefaction sand blows to study earthquake evidence before 1811. Dating of these prehistoric structures gives evidence that earthquakes in this area date back to 1450 and 900 A.D., (USGS, Putting Down Roots in Earthquake Country).
Current Research
This historical earthquake sequence of 1811 and 1812 was so powerful that it was felt in Charleston, S.C., Washington, D.C., New York City, Mexico, and Canada. Most earthquakes occur at plate boundaries, so why would one strike in the middle of a plate; the North American plate in this case? A recent 2009 Nova, PBS episode supports what so many scientists have reported since the 1970s. A theory given by Geologist Gary Patterson reiterates what most reliable text books have already told us that ~600 million years ago when the North American Continent was being pulled apart, a rift was created, but the rift failed creating a week spot. What’s known as the New Madrid Seismic Zone floats over this week spot, (Patterson). In trying to predict future earthquakes, studying rings in stalagmites in Midwestern caves and sediments deep below the Mississippi River give scientists’ information on the history of earthquakes in the NMSZ. Senior Geochemist Sam Panno and Geophysicist Beatrice Magnani set out to do just that. Panno has been studying Midwestern caves for years. In a cave in Illinois, Panno takes back core samples to be tested. Through chemical analysis of the crystals within the stalagmite, it is revealed that earthquakes in this area date back as far as 15 thousand years ago. In 2008 sending sound waves below the Mississippi River to study sediments in the Earth’s crust, Beatrice Magnami and her team discovered faults that stretched beyond the NMSZ. Magnami believes that because the Midwest danger zone shows a jumping pattern of earthquakes that it will be difficult to predict future Midwest quakes. But one thing is for sure, because there has been earthquake activity thousands of years before the 1811 and 1812 New Madrid earthquakes, there will be earthquake activity in the future, but when is the question, (Nova, Science Now).
Preparedness
The New Madrid Seismic Zone experiences more than 200 earthquakes a year. However they are not felt by humans as their magnitude is less than 1.0 to 2.0. Knowing that there is a very good chance that a future catastrophic earthquake will hit, careful preparedness has been put into place. St. Louis University, the University of Memphis, the U.S. Geological Survey and the University of Kentucky operate approximately 270 seismograph stations between St. Louis and Memphis to monitor earthquake activity in the New Madrid Seismic Zone and Central U.S., (Missouri, DNR).
If an earthquake were to strike the New Madrid Fault Zone today, by many scientific definitions, it will be catastrophic. Currently there are 12 million people in what’s considered the high-risk danger zone which includes the states Illinois, Arkansas, Tennessee, Kentucky, Missouri, Indiana, and Alabama. There are 44 million people in the entire New Madrid Seismic Zone region. The United States Geological Survey has estimated that there is a 7 to 10 percent chance that a major earthquake will happen in the New Madrid Fault Zone in any 50- year period with a magnitude of a 7.5 to an 8.0, (Virginia Tech), and a 90% chance of a 6.0 by the year 2040, (St. Charles Co. Health).
Theresa Jefferson and Jack Harrald research professors at the Virginia Tech. Center for Technology, Security, and Policy in the Nation Capital Region with extensive research, have put together a model reporting what the social impacts would be if the New Madrid Seismic Zone were to experience a 7.7 earthquake today and also reported on disaster response requirements needed for a magnitude at this level. According to their model, approximately 80,000 people would suffer injuries, and a possible 3,600 fatalities with close to 2 million seeking shelter within 72 hours and a total of ~7 million people in need of some kind of assistance. Over 100 hospitals will be damaged, and around 32,000 buildings would collapse which would result in needing search and rescue teams totaling upward of 42,000 people. Total economic losses could reach $300 billion. Harrald and Jefferson feel the population in this area does not take a threat of a possible earthquake seriously because it’s been so long since the last major quake. They are hoping the model they created will open people’s eyes and hope that some action will take place to prepare for such devastation, (Micale, Virginia Tech “Research” Magazine)
What is Being Done?
Lessons taken from Virginia Techs modeling, an action plan has been put into place. In 2006 FEMA provided funding for what is called The New Madrid Seismic Zone Catastrophic Planning Project and is headed by the Central U.S. Earthquake Consortium, (CUSEC), in an effort to develop, improve, and integrate the earthquake response plans of the eight states that are of major concern. They include: Alabama, Arkansas, Illinois, Indiana, Kentucky, Mississippi, Missouri, and Tennessee, (New Madrid Bicentennial).
The University of Alabama is currently constructing an Earthquake Simulator. A large steel table, called a shake table, is used and is designed to subject building design codes to close to actual seismic activity. Once researches know how certain buildings collapse they can develop better building codes going forward, (Tuscaloosa News).
On April 28, 2011 the first Great Central U.S. Shakeout was held with over 3 million participants in 11 states. Going forward it will be held annually on the first Thursday in February. The purpose of this event is to prepare the general public in the event that a similar 1811 quake hits Middle America again, (New Madrid Bicentennial).

Bibliography

Grayson, W. (February 12, 2012). Earthquake Simulator to be constructed at UA: Laboratory will be one of a kind in Southeast. Retrieved from http://www.tuscaloosanews.com/article/20120215/NEWS/120219833/1007?p=1&tc=pg Micale, B. L. (2012). Planning for the worst case for a mid-America quake. Virginia Tech “Research” Magazine, 22-25. 07319649. Retrieved on May 7, 2012 from EBSCO host

Middle America’s Fault It may some day cause another major earthquake. (1979). Time, 114(21), 66. 0040781X. Retrieved on May 3, 2012 from EBSCO host

New Madrid Bicentennial. (March 7, 2012). CUSEC New Madrid Catastrophic Planning Project.
Retrieved from http://newmadrid2011.org/

Nixon, J. Pauley, S. (n.d.). Facts about the New Madrid Seismic Zone. Missouri DNR. Retrieved from http://www.dnr.mo.gov/geology/geosrv/geores/techbulletin1.htm

Nova Science Now. (September 1, 2009). Earthquakes in the Midwest: Three massive earthquakes struck the American Midwest in 1811-12. Could it happen again? Retrieved from http://www.pbs.org/wgbh/nova/earth/earthquakes-midwest.html

St. Charles County Division of Emergency Management. (n.d.). About the New Madrid Fault Retrieved from http://www.scchealth.org/docs/ems/docs/prepare/newmadrid.html

The Encyclopedia of Arkansas History and Culture. (January 26, 2009). New Madrid Fault. Retrieved from http://www.encyclopediaofarkansas.net/entry-detail.aspx?entryID=2219

Thompson, G. Turk J. (2007). Earth Science and the Environment 4th Edition. Belmont, CA: Thompson Brooks/Cole

USGS. (n.d.). Historic Earthquakes: New Madrid 1811-1812. Retrieved from http://earthquake.usgs.gov/earthquakes/states/events/1811-1812.php USGS. (2011). Putting Down Roots in Earthquake Country: Your Handbook for the Central U.S. Retrieved from http://pubs.usgs.gov/gip/119/pdf/GIP119_ScreenVersion.pdf

Bibliography: Grayson, W. (February 12, 2012). Earthquake Simulator to be constructed at UA: Laboratory will be one of a kind in Southeast “Research” Magazine, 22-25. 07319649. Retrieved on May 7, 2012 from EBSCO host Middle America’s Fault It may some day cause another major earthquake. (1979). Time, 114(21), 66. 0040781X. Retrieved on May 3, 2012 from EBSCO host New Madrid Bicentennial