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Louisiana Earthquakes

Earthquakes Introduction

Earthquakes are one of the most devastating of earth’s natural events. Evident as a sudden violent trembling of the earth, this terrifying phenomenon has had a place in earth’s history even from the planet’s early days and continues to affect the world even now. Keenly observed since the dawn of the modern world, earthquakes have received mention as early as the 5th century BC in the work of Greek philosophers, and due to their significance are actively recorded today.

Earthquake reports gathered over time have made it possible to analyze and begin to understand earthquakes. Established quantitative scales allow for the comparison of earthquake impacts, with the recorded worst earthquake in history being the Valdivia earthquake of 1960 in Chile which rated a magnitude of 9.5 out of 10 on the Richter Scale. Furthermore, statistical data has made it possible to identify how many earthquakes happen a day, as the U.S. National Earthquake Information Center put the number at an approximate 55 worldwide (most of which are too small to be noticed and have little environmental impact). Geological studies have shed the most light on earthquakes, identifying different types of earthquakes and even explaining the mechanics behind them.

Science Behind Earthquakes

Earthquakes are caused by seismic waves, which are waves of energy that travel through the earth causing it to shake and become displaced. Seismic waves are generated when there is a sudden burst of energy within the earth. The point in the earth’s interior at which the energy is released is referred to as the hypocenter, and the point on the earth’s surface directly above the hypocenter is known as the epicenter of the earthquake. There can be multiple causes of such energy bursts including the subterranean movement of magma and accumulated volcanic gas (causing volcanic earthquakes), the collapse of underground mines (causing collapse earthquakes), the detonation of explosive weapons (causing explosion earthquakes), and the movement of tectonic plates (causing tectonic earthquakes). Tectonic earthquakes are the most frequent type of earthquakes that occur worldwide and are most likely to present a threat. To understand the mechanics of the occurrence of tectonic earthquakes, it is necessary to understand the inner workings of the earth.

The earth is composed of multiple layers, layers that differ in structure and composition from the visible surface to the deep interior. These are respectively named the crust (outermost layer), mantle, outer core, and inner core (innermost layer). The crust, which is the area of land visible as continents and the seabed, and the upper section of the mantle are the two regions related to the occurrence of earthquakes.

The earth’s crust is made up of rocks that cover the surface of the earth, forming a relatively thin shell over the mantle. This surface is, however, not a single continuous landmass, but several large distinct rocks that fit together like puzzle pieces. These are referred to as tectonic plates. Tectonic plates resting on the earth’s mantle move; very slowly, usually a few centimeters every year. As tectonic plates move, their edges being irregular rock surfaces tend to catch on each other and stick. This surface at which a discontinuity occurs in the rock is called the fault. The plates keep moving relative to each other and due to frictional forces, stress begins to build between the two adhering surfaces as they try to move past each other. Eventually, the stress builds up enough to force the two surfaces apart and is released as energy in the form of seismic waves. This is what causes an earthquake, as the seismic waves travel through the earth to the surface, causing the surface to shake and become displaced.

The intensity of the shaking produced by an earthquake at a point on the earth’s surface is measured on the modified Mercalli intensity scale. The shaking is measured from I to XII, with I being almost imperceptible and massive distortion of the earth occurring at XII. Through this scale, the strength of an earthquake can be gauged.

Earthquake Consequences

Earthquakes are significant environmental events that can affect us and the world in which we live in different ways. While most earthquakes are small enough to be unnoticeable, others are large enough to be considered natural disasters due to their catastrophic impacts. These impacts are a result of the different effects of earthquakes:

  • Ground tremors and the splitting of the earth

These are the primary consequences of earthquakes. The shaking of the earth can be small or extremely violent. This is a great part of the danger of earthquakes as the shaking can result in massive damage to structures and even lead to their collapse. The initial shaking might not even signal the end of the event, as large earthquakes produce aftershocks that can reinitiate shaking and further damage already weakened structures. The occurrence of soil liquefaction also becomes possible if the shaking is violent enough. Water-saturated granular materials such as sand behave more like a liquid than a solid when shaken enough, and structures resting on such surfaces may sink into them. Further damage can result from the ground splitting when blocks of earth move enough to separate at a fault.

  • Tsunamis

Earthquakes that occur on or near enough to the seabed can cause a displacement of the ocean floor. As a result, there is a sudden movement of a large body of water. This generates a series of sea waves with very long wavelengths that crash into coastal areas causing the loss of lives and destruction of property.

  • Landslides

Earthquakes can also induce landslides by destabilizing slopes enough to cause the movement of earth down the slope. Landslides on land pose a grave danger to buildings and people, as buildings can tilt and collapse. Landslides due to earthquakes can also appear underwater, these types of landslides referred to as submarine landslides can result in tsunamis if enough water is displaced.

  • Volcanic eruptions

Earthquake reports have drawn a correlation between earthquakes and volcanic eruptions. It has been identified that a large enough tectonic earthquake can cause a volcano to erupt. This is not to be confused with volcanic earthquakes that occur as a result of the underground movement of magma. A large enough earthquake can build up significant pressure in a volcano’s magma storage region prompting a premature eruption. This occurrence is, however, rare, as the volcano must be ready to erupt before the earthquake occurs.

  • Fires

The presence of electrical and gas lines in most modern cities severely increases the chances of a fire breaking out during an earthquake. The ensuing havoc a fire can initiate may even prove worse than the damage done by the earthquake itself.

  • Floods

The failure of dams is a possibility if an earthquake is powerful enough or strikes close enough. A dammed river suddenly bursting free spells disaster for whatever lies in its path during its forceful rush and may end up submerging areas.

Earthquake damage is not limited to the initial disaster that occurs. Even after the earthquake and its secondary events are over, persons affected may still suffer severely. Destabilization of a region may follow after a large enough earthquake, making it difficult for residents to gain access to necessities. It is also possible for survivors to suffer psychologically due to the traumatic event, even for years after the earthquake.

Louisiana Earthquake Threat Profile

Louisiana is located within the geological tectonic zone known as the Gulf Coast Basin; an area considered to have low to no seismicity. Louisiana in particular is a region of low seismic activity that does not rest on a tectonic plate boundary, but is instead marked by shallow growth faults in the northwestern and southern parts of the state. These growth faults allow for the movement of blocks of earth over long periods as sediments are deposited on or above the fault. This movement eventually causes a displacement of the land. These types of faults present the most danger to buildings than to people.

Seismic activity in Louisiana is more closely attributed to gradual creep along faults as opposed to the sudden movement along a fault resulting in an earthquake. Louisiana does still, however, have a history of experiencing earthquakes, but these are usually infrequent earthquakes with low magnitudes. The largest earthquake ever recorded in Louisiana occurred in 2006, 157 km south of Grand Isle with a magnitude of 5.3. Louisiana can also be affected by earthquakes occurring along fault lines in neighboring regions particularly in the New Madrid zone spanning Arkansas, Missouri, and Tennessee. The primary earthquake consequence experienced in Louisiana is tremors. Historical tremors have been strong enough to cause disturbances in water bodies, knock over unsecured items, and cause movements of heavy household furniture.

The United States Geological Survey (USGS) keeps records of earthquake locations in each of the country's states. The most recent earthquake in Louisiana occurred in April of 2021, 7 km west of Blanchard, and had a magnitude of 3.0. No damages or injuries have been reported regarding the event, but it was felt as far away as East Texas.

Preparing for Earthquakes in Louisiana

The threat of earthquakes in Louisiana is low, and the threat of massive earthquakes is even lower, but there still exists a potential for severe damage. Moreso if the strike occurs at a particularly unfortunate location. Therefore, anticipating possible dangers and establishing counters for them will be invaluable during desperate situations to prevent loss of lives and property damage when an earthquake hits. The USGS recommends the preparatory procedure advocated by the Earthquake Country Alliance (ECA) in planning for an earthquake. The ECA lists the following 4 things as part of an earthquake preparedness plan:

1. Secure your space

The foremost impact of an earthquake is the shaking that ensues. Violent shakings can topple furniture and toss around various household items, posing serious harm to people. Preventing items from moving when an earthquake begins is the first step to preparing for an earthquake. Heavy items such as bookcases, water heaters, and free-standing shelves should be moved away from gathering areas and exit routes. Next, secure these heavy items to walls using studs. Metal straps are suitable for pinning cylindrical items such as water heaters. Secure televisions and computers with straps to hold them in place. Use closed hooks to hang pictures and mirrors, also place heavy decorative items on lower parts of a shelf and secure them. The general rule of thumb for this step should be: if it can move, it must stay put.

2. Plan to be safe

Knowing exactly what to do when an earthquake starts will limit wasted actions, increasing response time to attend to the situation. This step advises the education of people on what to do during and after an earthquake. Either at a household, neighborhood, or work area, every person must know where to go and how to behave. The following actions are strongly recommended:

  • Designated safe locations such as panic rooms or under strong tables should be made known to everyone, and drills enacted to practice how to get to them

  • Communicate the location of utilities such as electricity, water, and gas along with the understanding of how to turn them off if needed (gas supply should only be turned off if there is a leak)

  • Smoke alarms are useful for detecting fires and halting their spread. Install smoke detectors and test them regularly to make sure they still work

  • Obtain training in basic first aid to become prepared to deal with minor medical issues

  • Obtain information about household members and neighbors to identify persons with special needs

  • Collaborate with neighbors to recognize persons trained to provide emergency response, persons who can help, and persons who may need help

  • Choose an accessible rendezvous point where a reunion can occur after the earthquake stops if separation happens during the event

  • Provide a list of emergency contact numbers that should be memorized, as well as the number of an out-of-area designated contact that can be reached if needed

  • Become familiar with the earthquake response plan in place at the school or daycare a child attends.

  • Identify temporary lodging options in the area that might be available if an earthquake damages the home enough to make it impossible to stay there.

3. Organize disaster supplies

Earthquakes create panic situations, situations that can escalate if an earthquake is severe enough. Disaster supplies are a necessary resource for navigating the difficult conditions of an earthquake and dealing with the aftermath. To be as prepared as possible, these are recommended disaster supplies to create:

  • Under-bed bags

An earthquake can occur while sleeping, and these supplies are meant for getting ready as quickly as possible. This bag should include essential items such as flashlights, shoes, whistles, dust masks, clothing, visual aids (glasses or contacts), and a crowbar. The supplies can be secured to the base of the bed to prevent them from getting loose if the house shakes.

  • Car kits

Car kits are supplies that will be needed on the go if an evacuation is necessary. Essential items include snack foods, bottled water, dust masks, spare visual aids, whistles, medical supplies, toiletries, emergency cash, maps, emergency contact numbers, flashlights, portable radio, batteries, and copies of personal identification documents. These supplies can be stashed in a car, and enough of them should be provided to last for about 3 days.

  • Home or office supplies

After an earthquake, it may be necessary to remain in the same location for several days. During this time, available supplies will make it possible to be self-sufficient while awaiting emergency response agencies. Essential supplies to have include canned foods, water (one gallon a day for each person), an off-grid cooker, cooking utensils, pet food, spare clothing, sleeping bags, medical supplies, toiletries, emergency contact numbers, fire extinguishers, flashlights, portable radio, batteries, wrenches, crowbars, gloves, sturdy shoes, and copies of vital documents.

Organizing supplies is a good preparatory action for responding quickly during an earthquake, but they can also serve well during other emergencies.

4. Minimize financial hardship

The damage an earthquake can cause to property is significant. Minimizing the financial loss as a result of an earthquake will help make the recovery process as smooth as possible. Consider obtaining earthquake insurance to make it easy to cover expenses that may arise after an earthquake. Making it harder for a building to be damaged by earthquakes should also be a point to consider for any aspiring homeowner. And finally, secure financial documents, such as insurance policies, make physical and digital copies to make it easy to recover them after an earthquake.

Earthquake Warnings and Alerts

Earthquakes are sudden events that are currently impossible to predict. Nevertheless, while it is not possible to know when an earthquake will occur, even in a region with high seismic activity, it is possible to know the exact moment it does. Early warning systems can detect the first seismic waves emitted by an earthquake which specialized machines analyze to determine if the earthquake is severe enough to warrant an alarm. If so, the information is relayed immediately to dedicated early warning services that can transmit this information to the public as an earthquake warning. The warning provided by such systems typically appears a few seconds before shaking starts, giving people and vehicles sufficient time to move away from structures that can fall.

An example of such a system is the ShakeAlert program operating in the West Coast states (Washington, Oregon, and California). Each resident is encouraged to download a mobile app that can receive a warning when an earthquake is about to start. Louisiana currently does not have an earthquake warning system, but it is expected that the ShakeAlert program will extend to cover other U.S. states in the future. Louisiana residents can subscribe to the USGS’s Earthquake Notification Service to receive information about earthquakes that occur in their area. This service is intended to provide earthquake information after they occur and not before.

Know Your Earthquake Risk

The location of a region on the earth's surface has a heavy influence on the region's susceptibility to earthquake events. Most earthquakes occur as a result of the movement of tectonic plates, and as a consequence, regions within the boundaries of plates are typically high-risk zones for earthquakes. Earthquakes can also occur in regions away from plate boundaries, though this is less common, and such areas are indicated by a history of earthquake activity.

Identifying earthquake active zones is best done using earthquake reports. These are a collation of data over several years indicating the frequency and strength of earthquakes that occur in the region. Such reports also detail important facts about the geological condition of the region such as specific soil types that can increase or decrease the severity of earthquakes. In the United States, earthquake reports can be accessed through the USGS or dedicated state geological services.

Additional state resources or community guidelines can further highlight specific earthquake hazards a region may suffer from. These are typically determined using historical data, scientific predictions, or simulations. Understanding the potential earthquake hazards of a region is important for knowing how much preparedness is needed to safeguard lives and property. Regions with low earthquake activity usually have lower preparedness levels, often recommending minimal earthquake preparatory response, while regions with high earthquake activity issue active warnings to prepare for earthquakes at any time.

During an Earthquake

The period during an earthquake event is an extremely critical moment, and all actions taken during this duration must be focused on preserving human lives. Publications by the USGS have established a comprehensive list of what to do during an earthquake. Adhere to each of the following safety precautions for earthquakes as soon as notification of an impending earthquake is received or shaking starts.

For persons indoors:

  • The most advocated action to take as soon as an earthquake starts is to Drop, Cover, and Hold On. This describes a sequence of three actions that can limit the injury a person may sustain during an earthquake. The first action to drop means to go down on all fours as this position lessens the risk of falling or being hit by flying objects. The second action to cover advises taking safety measures to protect vital organs. The first thing is to cover the head and neck with one arm and hand, the next is to seek shelter. If there is a sturdy table nearby, crawl under it. If not, crawl next to an interior wall without windows and stay bent over. The third action to hold on enjoins persons to remain where they are and keep protecting themselves until the earthquake stops. If under a table, hold on to it with the free hand and move with it if it shifts. If no cover can be found, stay bent over and cover the head and neck with both arms and hands.
    Persons using wheelchairs or walkers should lock their wheels, bend as low as possible, cover their necks and heads, and hold on until the shaking stops.

  • Stay away from windows to avoid flying glass, and away from heavy furniture to prevent injury if they collapse.

  • If in the kitchen when the earthquake hits, turn off any active fire source and leave the room immediately. Practice Drop, Cover, Hold On as soon as you leave.

  • Do not turn the gas on, and avoid creating any fire source, as gas leaks from broken pipes can lead to an explosion and fire.

  • Stay off the telephone lines unless for a fire or medical emergency.

  • Do not go downstairs and do not leave the house during this period.

For persons outdoors:

  • Remain outside for the duration of the shaking. Stay clear of anything that might fall, particularly buildings and power lines.

  • If in a car, remain inside. Park the vehicle and engage the hand brake. Do not park on or under a bridge, trees, power lines, or signs. Remain in the vehicle until the shaking stops.

  • If near the ocean, understand that a tsunami could be imminent. During the period of the shaking, practice Drop, Cover, Hold On until the shaking stops. As soon as the shaking stops, grab your emergency supplies and immediately move out of the evacuation zone or retreat to a high location or inland area.

After the Earthquake

At the end of the initial tremors of an earthquake, a portion of the danger has passed but the threat is still not over. The USGS recommends the following actions to further mitigate danger and injury:

  • Be prepared for aftershocks as these can also cause a lot of shaking. Get ready to drop, cover, and hold on again if shaking restarts.

  • Put on heavy-soled shoes to protect the feet from broken glass and rubble when moving around. Avoid moving about in rubble as much as possible.

  • Check for injuries in all persons present and provide first aid if qualified to do so. If not, maintain pressure on open wounds and avoid moving seriously injured people unless it is necessary to do so. Seek medical attention as soon as possible.

  • Ensure that fires are contained or cannot occur. Extinguish all fires if possible or call for help in case of large fires. Turn off gas valves if gas pipes are broken or the odor of gas persists. Do not light a fire during this period. Shut off the house’s electricity at the control box if there is a suspicion of damaged wiring.

  • Trapped persons should try as much as possible to attract attention. Bang repeatedly on pipes and loud items until someone comes.

  • Maintain food and water supplies until the situation stabilizes.

  • Move away from buildings that are heavily damaged or show a risk of collapse.

At the end of an earthquake event, recovery can begin. Damaged buildings can be repaired and interrupted utilities restored. Earthquake insurance can come in very handy in this instance to cover damage expenses. Finally, it all comes to an end, and the next thing to do is begin to prepare for the next one.