The trembling or shaking of the Earth, sometimes known as an earthquake, is caused by the movement of tectonic plates under its surface. The earth’s crust is divided into large and small pieces known as tectonic plates. These plates are constantly moving, albeit slowly, because to the heat created by the Earth’s core.
When two tectonic plates grind against each other, they may become trapped due to friction. As the plates continue to move, stress accumulates along the fault line until it is released in the form of seismic waves, causing the ground to shake. This discharge of energy is what we experience during an earthquake.
Earthquakes can also be produced by volcanic activity, landslides, or even human activities like mining or reservoir-induced seismicity (which occurs when big reservoirs are filled behind dams).
Earthquakes range in magnitude and severity, from mild tremors that are hardly visible to catastrophic ones that inflict major damage and loss of life. Understanding the causes and mechanisms of earthquakes is critical for reducing their impact and maintaining community safety in earthquake-prone areas.
Where earthquakes do occurs?
Earthquakes can occur anywhere on Earth, but they are more common around tectonic plate borders. These boundaries include:
Divergent Boundaries: These are areas where tectonic plates are moving apart from one another. Earthquakes at divergent borders are typically small, but they can occur as the crust extends and splits.
Convergent Boundaries: These are zones where tectonic plates collide with one another. Earthquakes near convergent borders can be quite violent, and they are frequently connected with subduction zones, in which one tectonic plate is thrust beneath another.
Transform Boundaries: These are the areas where tectonic plates glide past one other horizontally. Earthquakes at transform borders are usually generated by friction between the plates as they pass each other.
Intraplate earthquakes occur within tectonic plates, away from plate borders. These can occur due to a variety of reasons, including the reactivation of ancient faults within the plate or volcanic activity.
The complicated interactions of tectonic plates cause some places of the earth to be more seismically active than others. The Pacific Ring of Fire, for example, is a seismically active zone that surrounds the Pacific Ocean and where multiple tectonic plate boundaries intersect, resulting in frequent earthquakes and volcanic eruptions.
How do we measure the intensity of earthquakes?
Earthquake intensity is commonly quantified using two basic scales: the Richter scale and the moment magnitude scale (abbreviated as Mw). These scales provide numerical figures for measuring the energy released by an earthquake and its possible impacts. Here’s a quick overview of each:
Richter Scale: The Richter Scale, developed by Charles F. Richter in 1935, estimates the amplitude of seismic waves generated by an earthquake. The Richter scale is logarithmic, which means that each whole number increase corresponds to a tenfold rise in recorded amplitude and approximately 31.6 times more energy release. This scale, however, does not reliably measure greater earthquakes because it saturates at higher magnitudes.
Moment Magnitude Scale (Mw): The moment magnitude scale (Mw) was established in the late twentieth century to estimate the overall energy produced by an earthquake. It considers the area of the slipped fault as well as the quantity of slip that occurred. The moment magnitude scale is now the recommended method for estimating earthquake magnitude because it provides a more accurate picture of an earthquake’s size over a wide range of magnitudes.
In addition to quantifying earthquake magnitude, the Modified Mercalli Intensity (MMI) scale is frequently used to assess earthquake intensity in terms of shaking felt at a specific site. The MMI scale assigns Roman numeral values ranging from I to XII based on observed impacts on people, structures, and the natural environment. These numbers describe the perceived shaking and the associated damage in certain regions. Unlike magnitude scales, which assign a single numerical value to an earthquake, intensity scales provide information about the localised impacts of shaking at various sites.
What damages can earthquakes cause?
Earthquakes can produce a variety of damages, depending on the size of the quake, the depth of the earthquake’s focus, the distance from the epicentre, the local geology, and the quality of construction in the affected area. Earthquakes may produce the following types of damage:
Structural Damage: Buildings, bridges, roads, and other infrastructure can sustain damage ranging from slight cracks to total collapse. The level of structural damage is determined by elements such as design and construction standards, shaking duration and intensity, and building material types.
Landslides: Earthquakes can create landslides, especially in mountainous or hilly areas where the shaking destabilises slopes and causes rocks, soil, and debris to slide downward. Landslides can cause structural damage, restrict roadways, and endanger residents.
Tsunamis: Underwater earthquakes, especially those that occur near subduction zones or tectonic plate borders, can cause tsunamis. These massive ocean waves can travel great distances and inflict enormous devastation along coastlines, including floods, damage to coastal infrastructure, and loss of life.
Liquefaction: In regions with loose, water-saturated soil, an earthquake’s strong shaking can result in liquefaction. This process weakens the soil and causes it to behave like a liquid, causing structures and infrastructure to sink, tilt, or even collapse.
Fire: Earthquakes can burst gas lines, start electrical fires, and impede firefighting efforts, resulting in the outbreak of flames in impacted areas. Fire can inflict significant damage to buildings and infrastructure, amplifying the effects of an earthquake.
Infrastructure Disruption: Earthquakes can disrupt critical services such as water supply, energy, transportation, and communication networks, making it difficult for emergency responders to deliver help and impacted people to obtain basic requirements.
Psychological and Societal Impact: Beyond physical devastation, earthquakes can have a significant psychological and sociological impact, creating dread, anxiety, and trauma among afflicted communities. Disrupting communities, displacing people, and losing livelihoods can have long-term social and economic implications.
How do we save ourselves from earthquakes?
Individuals and communities can take many measures to lessen the risk of injury, minimise property damage, and improve overall resilience to earthquakes.
Prepare an Emergency Kit: Prepare an emergency kit with items such as water, non-perishable food, prescriptions, first aid supplies, flashlights, batteries, a portable radio, and critical documents. Keep the kit in an easily accessible location.
Create an Emergency Plan: Create a family emergency plan that includes evacuation routes, meeting locations, and communication procedures in the case of an earthquake. Make sure that everyone in the family understands the strategy and that drills are practiced on a regular basis.
Secure Heavy Items: To avoid heavy furniture, appliances, and other large items from tipping over during an earthquake, secure them to walls or floors with straps, brackets, or anchor bolts.
Reinforce Buildings: Building reinforcement entails retrofitting older structures to increase structural integrity and seismic resistance. This could include reinforcing walls, foundations, and connections, as well as installing seismic bracing or dampers.
Identify Safe Spaces: Locate secure areas in your house or business where you can seek refuge during an earthquake, such as behind robust furniture or against interior walls away from windows, mirrors, and heavy objects.
Practice Drop, Cover, and Hold On: Teach everyone in your household the “Drop, Cover, and Hold On” approach for earthquake protection. Drop to the ground, seek refuge beneath a substantial piece of furniture, and hold on until the shaking stops.
Stay Informed: Stay up to date on earthquake dangers in your area by monitoring local seismic activity and following emergency management guidelines. Sign up for alerts and warnings from your local emergency notification systems.
Secure Hazardous Materials: Store hazardous materials, chemicals, and flammable liquids in specified areas to avoid accidents or leaks that could pose additional risks during an earthquake.
Plan for Recovery: Create plans for post-earthquake recovery, such as temporary housing, medical care, and access to critical services. Collaborate with neighbours, community organisations, and local governments to plan response and recovery efforts.
Educate Yourself: Learn more about earthquakes, including their causes and potential consequences. Stay up to date on best practices for earthquake preparedness and response by using educational resources from government agencies, non-profit organisations, and community groups.
What does Tsunami occurs?
A tsunami happens when a huge volume of water is swiftly displaced, usually as a result of undersea seismic activity such an earthquake, volcanic eruption, or underwater landslip. The abrupt displacement of water causes a sequence of huge waves to propagate outward from the source area and move at high speeds over the ocean.
The most prevalent cause of tsunamis is undersea earthquakes, particularly those that occur at subduction zones where tectonic plates collide. When an earthquake shifts the seafloor, it can cause vertical displacement in the water column above, resulting in the production of a tsunami wave.
Tsunami waves can rush across the ocean at speeds of up to several hundred kilometres per hour (about 500 miles per hour), yet their wave heights are comparatively low. However, once the waves approach shallow coastal areas, their speed slows and their height rises substantially, frequently resulting in catastrophic floods and destruction along coastlines.
Tsunamis aren’t like regular ocean waves. Instead of a single wave crest, they are made up of several waves, with the initial wave rarely being the largest. This series of waves can last for several hours, making it difficult to estimate the exact timing and magnitude of the tsunami’s impact on coastal populations.
