According to the United States Geological Survey (USGS), earthquake prediction in the Midwestern States during the next 50 years is 25-40% probability of having an earthquake magnitude of 6.0 or greater generated from the New Madrid Fault in Southeastern Missouri. A New Madrid Earthquake of magnitude 7.0-8.0 similar to any of the three large earthquakes of 1811-1812 has a 7-10% probability of occurrence. Such earthquake scenario would cause substantial economic losses in Tennessee, Missouri, Kentucky and Illinois. Heavy earthquake damage of unreinforced masonry buildings in Memphis TN is expected. Recent earthquakes in 2010 Haiti and 2011 Japan serve as a wake up call for earthquake preparedness and emergency preparedness in the Midwest that has lagged far behind as compared to the West Coast. Earthquake preparedness requires homeowners to be aware of the location of their home with respect to the New Madrid Fault and areas of soil liquefaction shown on USGS maps, and knowledge on factors influencing earthquake damage to their homes. It also requires a plan for disaster preparedness to ensure home safety through seismic retrofitting and risk mitigation of home contents. Earthquake insurance is an effective option in addition to or in lieu of seismic retrofitting. Emergency preparedness requires purchasing earthquake survival kit for the household, emergency kits for household members, as well as emergency food and water for at least 2 weeks.
Earthquake Information on the New Madrid Fault
The potential for a moderate-to-large New Madrid Earthquake exists in the Midwest where three of the largest historical earthquakes occurred in the winter of 1811-1812 within the New Madrid Fault in Southeastern Missouri. The three main earthquakes of magnitude 7.0-8.0 occurred on December 16, 1811; January 23, 1812; and February 7, 1812. The New Madrid Fault stretches from the west of Memphis in Tennessee into Southern Illinois and consists of three fault segments: the northeast and the southwest segments which are strike-slip fault lines, and the Reelfoot which is a thrust fault. Earthquakes in the Midwest are less frequent than in California. However, they affect much larger areas because the Midwest is a more stable region in which the energy released from an earthquake is transmitted into the surrounding regions more efficiently, while the energy is relatively quickly absorbed in California, as shown in the figure below. The magnitude 7.8 San Francisco Earthquake in 1906 was felt 350 miles away in the middle of Nevada, while church bells rang in Boston Massachusetts from the magnitude 7.5 New Madrid Earthquake of December 1811, which is 1,000 miles away. Therefore, seismic activity in the New Madrid is capable of causing widespread damage over a large region in Midwestern States. The region of potential impact due to a New Madrid Earthquake is comprised of eight states: Alabama, Arkansas, Illinois, Indiana, Kentucky, Mississippi, Missouri, and Tennessee.
Earthquake Damage to Buildings
Back- and forth- ground shaking, soil amplification and soil liquefaction are the main reasons for earthquake damage to your home, although landslides and fires are also possible factors that affect your home safety. Deep soils in the Mississippi River Valley would shake more than bedrock in the hills as a result of persistent shaking where seismic waves are trapped and reverberate. Areas of liquefaction occurs in the Midwest within: a) The Central Mississippi River Valley including the Reelfoot Scarp, the New Madrid Fault, and the Western Lowlands liquefaction features; and b) The Mississippi and Ohio Rivers Regions including the Wabash Valley and St. Louis-Cape Girardeau liquefaction features (source: .
The region within and surrounding the New Madrid Fault is home to millions of people including those in the metropolitan areas of St. Louis MO and Memphis TN. Most buildings were not built to withstand earthquake shaking. Wooden houses are the most prevalent building type in the Midwest, while unreinforced masonry homes comprise a much smaller portion of the regional building inventory. A recent study by the Mid-America Earthquake Center demonstrates that residential buildings would incur more earthquake damage than any other building usage. In addition, earthquake damage to unreinforced masonry buildings at much higher percentage than wooden houses even from moderate ground shaking. Over 250,000 buildings in Tennessee are expected to be moderately-to-severely damaged from rupture of the southwestern segment of the New Madrid Fault. At least 50,000 are moderately damaged unreinforced masonry buildings. Over 80,000 buildings are expected to be damaged in Missouri.
Earthquake damageoccur if homes are not effectively bolted to the concrete foundations, the cripple walls are not braced, or the existence of a soft story in houses with large openings (e.g. garage doors or windows) at the first level without effective bracing. Structural damage is also influenced by building materials, year built, and number of stories.
Seismic Retrofitting for Home Safety
You should seismic retrofit your home if it is built of unreinforced masonry, or if you live within the New Madrid Fault or 25 miles around it, which is represented by the red, orange and probably the yellow contours of the USGS earthquake map shown below. If your home is constructed before the 1980s or if you live in the areas of liquefaction mentioned above, you probably need to retrofit it. More on steps of seismic retrofitting and costs can be found at http://seekyt.com/earthquake-preparedness-in-california.
Risk Mitigation of Home Contents
You should mitigate the contents of your home whether you seismic retrofit it or not in order to reduce the risk to lives and investments. Risk mitigation measures are simple techniques that can be undertaken by homeowners to secure the non-structural elements and home contents to the studs of the interior walls or floors using inexpensive hardware tools and materials found in hardware stores. You should secure tall and heavy furniture using earthquake straps, or fragile and expensive objects using Quake Hold or Museum Wax. Items in the garage shall be secured to reduce damage to vehicles. Water heaters should also be braced to the wall studs with two heavy-gauge metal straps and lag screws near the top and bottom of the tank, which would cost $20 to $200 but will save several thousand dollars in repairing fire or flood damage if left unsecured.
Homeowners insurance does not cover earthquake damage to your home, home contents, or personal belongings, but covers other kinds of damage that may result from earthquakes, such as fire and water damage due to burst gas and water pipes. Your vehicles are only covered under the comprehensive part of your auto insurance policy. You will also be responsible for your existing personal debt even if your home is destroyed. Earthquake insurance is an effective way to protect your assets and investments from the potential costs of destructive earthquakes, especially if you did not seismic retrofit your home. The states of Missouri, Tennessee, Illinois, Kentucky, and Indiana are among the top 10 largest markets for earthquake insurance coverage whose annual rate varies by home location, year built, construction material, and insurance company. Older buildings cost more to insure than newer ones, while wooden houses benefit from lower rates than unreinforced masonry homes.
It would be helpful to take the Red Cross first aid and cardiopulmonary resuscitation emergency training course. In the meantime, emergency preparedness shall be developed and maintained before a New Madrid Earthquake hits your area, which include the following purchases that are available from online stores:
Earthquake Survival Kit for your household inside a large watertight container stored in an easily accessible outdoor location other than the garage. It shall include first aid kits, cooking utensils, gas grill, flashlight, wrench, work gloves, protective goggles, heavy-duty plastic bags, soap, toothpaste, toilet paper, comfortable warm clothing, baby items, blankets, sleeping bags or a tent, and an emergency radio.
Emergency Kits for household members that are collection of first aid supplies including flashlight, whistle, dust mask, sturdy shoes, bottled water, snack foods, hygiene supplies, emergency contact, emergency cash, medications, spare eyeglasses or contact lenses, and cleaning solutions.
Emergency Food and Water shall be maintained for at least 2 weeks in your household emergency kit. A minimum of one gallon per household member per day of emergency drinking water is essential while the emergency food shall be canned and packaged.