An earthquake is the rapid shaking of the earth’s surface resulting from the sudden release of energy generated when tectonic plates slip past one another. Several earthquakes occur yearly, with only a few being noticeable. But when they are, earthquakes can be devastating. Major ones can result in extensive property damage, loss of lives, and other disasters such as fires, landslides, and tsunamis. The 1964 Great Alaska Earthquake, the worst ever recorded in United States history, resulted in 129 fatalities and an estimated economic loss of $2.3 billion (in 2013 dollars).
Mississippi is not considered one of the areas with high-risk earthquakes in the United States. But its residents are likely to experience the effects of large earthquakes in nearby states, which makes it a good idea for them to learn how to prepare for one.
Earthquakes result from geological activities in sections of the earth's crust, known as the tectonic plates. Tectonic plates constantly move over molten rocks in the earth's mantle. Sometimes they get stuck at their edges while moving against each other, causing friction to build up between them. When there is enough stress to push the plates past one another, they suddenly unstick, causing the instant release of energy known as seismic waves. The waves travel to the surface, causing intense shaking that is felt on the ground.
The point or break in the earth’s crust where the tectonic plates suddenly slide past each other is known as the fault or fault plane. Likewise, scientists refer to the place the earthquake begins below the surface of the earth as the hypocenter. The equivalent area on the surface is known as an epicenter.
Earthquakes are usually preceded by foreshocks which are minor ground shaking that occurs in an area before the actual disaster or mainshock. After the mainshock, affected areas also experience mild ground shaking, usually referred to as aftershocks. Intense ground shaking caused by earthquakes can last from a few seconds to a few minutes.
Earthquakes are classified into four categories based on the circumstance surrounding their occurrence and the geological makeup of where they occur. They include tectonic, volcanic, collapse, and explosion earthquakes.
Tectonic earthquakes are the most common types of earthquakes. They are caused by the movement of the tectonic plates. In contrast, volcanic earthquakes are caused by volcanic eruptions in nearby areas, while explosion earthquakes are triggered by nuclear or chemical explosions. Collapse earthquakes happen as a result of the collapse of underground caverns and mines. Therefore, earthquakes can occur either as a result of natural geological factors or human activities, or a combination of both.
Mining is one of the most common human activities that trigger earthquakes. The process of removing large amounts of rocks and minerals from the ground makes the earth’s crust unstable, resulting in earthquakes. Hydraulic fracturing or fracking also contributes to an area’s earthquake risk. It involves the use of high-pressure water injection to break down rock formations and extract petroleum resources. The method of disposing of chemically-contaminated water by injecting them into deep wells can also induce earthquakes.
Furthermore, the operation of dams remains the leading cause of powerful human-triggered earthquakes. The weight of the large volume of water held back by a dam can cause stress to build on the surface beneath and trigger an earthquake. Notably, the largest human-triggered earthquake on record was caused by the fault line beneath the Zipingpu Reservoir in China. The earthquake, which occurred in 2008, had a magnitude of 7.9 and resulted in about 80,000 deaths.
Similarly, the enormous energy released by nuclear explosions can stress fault lines and cause earthquakes to occur. An example of this is the 2017 underground nuclear explosion test conducted at North Korea’s Punggye-ri, which caused several earthquakes for months.
Mississippi does not experience many human-induced earthquakes. Its earthquake risks are linked to nearby fault lines.
Earthquakes can be classified based on their magnitude and intensity. Magnitude is the measurement of an earthquake’s size based on the amount of seismic energy released during its occurrence. It is calculated based on recordings by seismographs during the disaster. There are several scales used to determine an earthquake’s magnitude, but the Moment Magnitude Scale is commonly used by seismologists in the United States. Earthquakes’ magnitudes are assigned on a scale of ten, with stronger earthquakes getting higher values. The 1964 Great Alaska earthquake, the largest in the United States, had a 9.2 magnitude.
An earthquake only has one magnitude value, irrespective of where it was measured. In contrast, intensity describes the severity of the earthquake in terms of the degree of shaking and damage experienced in a particular area. It varies depending on the distance from the earthquake’s epicenter. The Modified Mercalli Intensity Scale is currently used to measure earthquake intensity in the United States. It uses the roman figures from I to X to rate the direct effects of an earthquake in a particular area. Lower values measure how noticeable an earthquake is to normal people, while values from VIII and above usually involve considerable damage to buildings and infrastructures.
|Nature of Impact or Damage
|Unnoticed except under favorable circumstances.
|Noticeable only to people at rest, such as those upper levels of buildings.
|Felt by persons indoors but not initially recognized as an earthquake. They might likely rock static cars.
|More noticeable, with walls making cracking sounds, dishes, windows, and doors are affected.
|Dishes and windows may break, and unstable objects may overturn
|Noticeable to many people. Shaking can move heavy furniture, fall plasters, and cause other slight damage.
|Earthquakes of this intensity can cause negligible damage in well-designed and built structures, slight to moderate damage in ordinary structures, and considerable damage in poorly built buildings.
|Slight damage in specially designed structures, considerable damage in ordinary substantial buildings, and great damage in poorly designed buildings. Typical damage includes the fall of chimneys, factory stacks, columns, monuments, and walls. Overturning of heavy furniture.
|Considerable damage to specially designed structures, and substantial damage to other buildings, including partial collapse or shifting the building off its foundation
|Catastrophic damage, including the total destruction of wooden, frame, and masonry structures.
Finally, earthquakes can strike anywhere at any time without warning. But most large earthquakes occur in areas between tectonic plates, known as plate boundaries. The most seismically active region of the world is the Ring of Fire - a string of volcanically active areas around the edge of the Pacific Ocean.
The primary consequence of an earthquake includes ground shaking, surface rupture or faulting, landslides, soil liquefaction, and tsunamis.
Ground Shaking: This is caused by the seismic waves released during the earthquake. Depending on the earthquake’s magnitude, ground shaking can be minor or intense enough to destroy buildings, roads, and bridges. The intensity of ground shaking reduces as one gets farther from an earthquake’s epicenter.
Surface Rupture or Faulting: This occurs when plate movements along a fault plane break to the surface above, causing an offset on the ground. Surface faulting can severely damage homes and infrastructures.
Soil Liquefaction: The intense shaking from an earthquake can cause soil sediments beneath an area to break apart and become fluid, resulting in the collapse or severe damage of structures built on them.
Landslides: Earthquakes can cause weak soils on a hillside or mountain to fail, causing a massive downhill movement capable of clearing anything in its path. Debris from landslides can destroy buildings, block roads, and disrupt utility lines.
Tsunamis: Underwater earthquakes can offset ocean floors resulting in the displacement of a large volume of water that can hit coastal areas and cause significant damage.
In addition to their primary effects, earthquakes can also spawn secondary hazards like fires, which occur as a result of the rupture of electrical and gas lines during the disaster. Similarly, large tectonic earthquakes can also trigger volcanic eruptions in nearby areas under certain conditions.
Mississippi is located in the Southeastern region of the United States. As of 2020, the state has a population of 2,961,279 people and a land area of 46,923.96 square miles. Based on current seismological data, the state is considered a low-magnitude seismicity area, which means it is less likely to experience large earthquakes. In fact, in the last 200 years, only four earthquakes of intensity level V or higher have occurred within its borders. Nonetheless, earthquakes of smaller magnitudes have caused some damage in the past. For example, a 4.7 magnitude earthquake caused damage to buildings in Charleston, Tallahatchie County, in 1931. Likewise, the town of Greenville in Washington County experienced minor damage from the occurrence of a magnitude 4.3 earthquake in 1967.
The state’s greatest earthquake risks are linked to occurrences in nearby seismically active areas, particularly the New Madrid Seismic Zone. Areas in this zone include northeastern Arkansas, southwestern Kentucky, southeastern Missouri, and northwestern Tennessee. Between 1811 and 1812, the area experienced a series of earthquakes, including three large ones with magnitudes between seven and eight. The largest of the earthquakes severely affected settlements along the Mississippi River and caused the river banks to cave in.
Here are some notable earthquakes that have occurred in Mississippi, including their magnitudes, areas affected, and intensities.
|May 3, 1977
|Southeastern Clarke County
|November 4, 1977
|Vardaman, Calhoun County
|December 10, 1978
|Southeastern Clarke County
|February 5, 1983
|Northeastern Prentiss County
|May 10, 2008
|Belden, Lee County
Earthquakes occur suddenly, without any warning. Therefore, residents need to prepare ahead to avoid or limit casualties when one strikes. The following steps can help Mississippi residents prepare ahead of the disaster.
Determine how to respond when an earthquake occurs and practice it with your family. Your plan should consider your pets and also include a means of communication. You can also mark out shelters and hotels that accept pets in case you need to leave your home because of the disaster. Also, identify both safe and dangerous spots in your building. Furthermore, learn how to shut off utilities, Drop, Cover, and Hold On, apply first aid, and use a fire extinguisher.
The kits should include supplies that would sustain you, your family, and your pet immediately after the disaster. It should contain bottled water, non-perishable foods, a can opener, first aid and sanitary supplies, blankets, flashlights, and a battery-powered radio. Your pet’s toys, medicine, and food should also be included. Ensure that the kits are easily accessible.
Poorly designed and constructed buildings can suffer considerable damage during earthquakes and endanger the people in them. Amendments that can be made to ensure that buildings and their contents are less susceptible to damage during an earthquake include:
Anchoring your building to its foundation
Making necessary structural repairs
Ensuring that utility lines are not defective
Bracing heavy furniture to walls
Anchoring overhead fixtures and lighting
Fastening water heaters and gas appliances to wall studs
Keeping breakable objects on lower shelves.
Ensure that any repairs and construction work in your home is done in line with your locality’s building and seismic codes.
Ensure that your vehicle is in good condition and fully fueled all the time. This is important in case you need to evacuate. Also, keep an emergency kit and a fire extinguisher in your vehicle. Avoid keeping extra fuel in your vehicle’s trunk. The intense shaking can make it spill.
Develop a savings plan to cover your emergency response and ensure that you always have some cash with you. Insurance is important as well. Traditional homeowners insurance does not automatically cover earthquake damage. You would require separate coverage. However, comprehensive auto insurance would typically cover damage caused to your vehicle by an earthquake.
There is no way to predict the occurrence of an earthquake at the moment. But early warnings and alerts notify residents of an area of imminent earthquakes that can affect them. These warnings usually arrive very close to the occurrence of earthquakes. Still, they are important, as a few seconds can make a difference in one’s disaster response. The alerts are issued to a particular area when sensors pick up an earthquake’s compressional or P waves, which travel faster and are less noticeable. Before the more destructive transverse or S waves hit the area.
Mississippi residents can receive email and text notifications about imminent and ongoing earthquakes around them by signing up for the Earthquake Notification Service (ENS). Wireless Emergency Alerts (WEA) are also disseminated to the cell phones of residents whose emergency alert settings are on. You can also check the Mississippi Emergency Management Agency’s website for a list of active warnings and alerts in the state. Furthermore, local and municipal governments usually maintain a notification system for their residents. Ensure that you contact your local authorities to learn about their emergency alert system and sign up for it.
It is crucial to be alert at all times, as signs of an earthquake may begin to become obvious even before alerts or warnings reach you. As such, immediately you begin to feel the ground shaking, take action to protect yourself, your family, and your pets.
Understanding your area's earthquake risk helps you prepare better for the disaster and its impacts. Your earthquake risk is not only a function of your area's seismic hazard or likelihood of experiencing earthquakes. Factors like population and quality of construction also contribute significantly to an area’s risk. Furthermore, some areas are more susceptible to the effects of earthquakes than others. Notably, areas around mountains and hills are more likely to experience landslides. Meanwhile, liquefaction is more common in areas with soft soil sediments.
You can learn about your area’s risk by checking up on the National Seismic Hazard Map, which contains location-specific earthquake data. You can also check how close you are to fault lines in the country. But for more comprehensive and specific information about your area, contact your local emergency officials to know your seismic zone and get location-specific safety tips. Some local governments also provide updates about earthquake risks on their website.
Once you get a warning or notice signs of an earthquake, follow the steps that apply to where you are to keep safe during the disaster.
Take shelter under sturdy furniture, like a table or desk, and Drop, Cover, and Hold On till the vibration ceases. In detail, drop to the ground, take cover under the furniture and protect your head and neck with your arms, and hold tight to the furniture until the earthquake is over.
If you cannot find sturdy furniture, go to an inside corner of the building, drop down and protect your head and neck.
Avoid using elevators
Stay away from glass windows to avoid injuries from shattered glass
Stay away from outer doors and walls as well as lighting fixtures and furniture, as they can fall during an earthquake.
If in bed when an earthquake strikes, stay there, curl yourself, and protect your head and neck with a pillow. However, do not hesitate to move to a safer spot if you are under a heavy light fixture that is likely to fall.
Avoid standing in doorways unless you are sure they are strongly supported.
Look out for your pets to ensure that they follow your direction.
Turn off your stove immediately if you happen to be cooking when an earthquake strikes.
Limit your movement. Only move after the shaking has totally stopped.
Find an open place to wait out the shaking.
Stay away from buildings, trees, power lines, and streetlights.
Be extra cautious when around mountainous areas to reduce the risk of debris and rocks hitting you.
Identify a clear area, pull over there, and apply your parking brake.
If possible, stay away from signs, buildings, trees, bridges, overpasses, power lines, and any other object or structure that can collapse or fall.
Remain in your vehicle, fasten the seatbelt, and protect your neck and head with your arms till the shaking stops.
Do not exit your vehicle if a power line falls on it. Instead, call 911 and wait for assistance.
Be wary of areas around mountains and hills. They are susceptible to landslides that can bring debris your way. Also, watch out for falling rocks.
Mississippi residents should take the following steps after an earthquake to address damage and injuries and avoid further hazards.
Reach out to everyone using your emergency communication plan. Check for injuries and apply first aid if necessary. Get immediate medical help for serious injuries by calling 911. Ensure that your pets also get medical care after the disaster. Furthermore, if you are trapped in rubble or debris, protect yourself from dust by covering your mouth and nose with clothing. Try to attract the attention of rescuers by tapping a pipe or wall or using a whistle. Shouting should only be the last option as it can make you inhale a lot of dust. Also, avoid kicking up dust and lighting a match or lighter.
Check for structural damage, affected utility lines, and destroyed appliances. Do not cause a spark, as it can trigger an explosion. If you turn off your utilities, do not turn them back on yourself. Instead, contact a licensed contractor. Also, do not stay in your building until it is declared safe by local authorities.
Wear protective clothing and sturdy shoes to avoid getting injured by sharp debris. Also, clean up medicines and flammable substances immediately and ensure that children do not loiter in damaged areas. If you hear a hissing sound or perceive the smell of gas, leave the building immediately and call 911. There might have been a gas leak.
Take pictures and videos of damage caused to your home and belongings, and contact your insurance agent on time. Only make repairs to prevent further damage. Leave permanent repairs till you have consulted your insurance agent or company.
Con artists posing as contractors usually try to scam residents of disaster-hit areas. To avoid falling for fraudulent contractors, hire only licensed contractors. You can verify a contractor's license status online. Aggrieved residents can report scammers to the state’s Attorney General’s Office or file a complaint with the Board of Contractors.
Do not drive on damaged roads, bridges, and ramps. Also, avoid driving close to downed power lines and damaged buildings. Continue to watch out for landslides and debris falls. Choose upper ground when driving in coastal areas susceptible to tsunamis.
Stay tuned to local radio for recent updates on the disaster, secondary hazards, and safety tips. Also, expect further shaking from the earthquake’s aftershock.
After a disaster, the President can make a Disaster Declaration over affected areas to ensure residents get the required help following the disaster. The Federal Emergency Management Agency (FEMA) usually provides feeding, temporary accommodation, and debris clean-up assistance in affected areas. The Internal Revenue Service (IRS) also provides tax relief to people in affected areas.