Saturday, December 2

What Is an Earthquake And What Are Its Types?


An earthquake is an intense shaking of the Earth’s surface and is one of the many natural disasters. It has destroyed property and taken thousands of lives throughout the years. In reality, there are about 50 and 80 earthquakes per day, or roughly 2000 per year, according to statistics.

It is challenging to predict how much harm an earthquake will leave behind before it happens. If you are interested in knowing what is an earthquake? Then here’s a detailed explanation about all you need to know about earthquakes:

Types of earthquake

The earthquakes explained here are differentiated into four main types:

  1. Tectonic earthquake

Earth’s plates that move together result in tectonic earthquakes. These earthquakes discharge a tremendous amount of energy that has the potential to do great harm. This can happen when two plates touch, when one plate slides under another, or when the mantle moves and pushes one plate to move.

  1. Volcanic earthquakes

Volcanic earthquakes are caused by magma moving beneath the surface of the Earth. Though these earthquakes are often smaller than tectonic earthquakes, they are still capable of doing a great deal of harm.

  1. Explosions earthquakes 

The detonation of explosives is the cause of explosion earthquakes. Even though these earthquakes can be minor, they can still cause harm if they happen close to populous areas. Several factors, such as mining, building, or conflict, might cause this type of earthquake.

  1. Collapse earthquakes

Collapse earthquakes are caused by the collapse of buildings or other structures. These earthquakes are normally rather small, but they can be deadly if they strike a densely populated area. Poor construction, extreme weather, or an earthquake are a few causes that could lead to this type of earthquake.

Why Do Earthquakes Happen?


Although the Earth appears to be stable then, why do earthquakes happen? It is because the Earth is actually very active under the surface. A solid crust, a nearly solid mantle, a liquid outer core, and a solid inner core are the Earth’s four basic layers.

The lithosphere is a region made up of the dense crust and the uppermost, hard layer of the mantle. The lithosphere does not cover the entire Earth like an eggshell in one continuous layer. Huge puzzle pieces called tectonic plates make up the lithosphere’s true composition.

The viscous, or slowly moving, mantle layer beneath the tectonic plates causes them to move continuously. The Earth’s crust is put under stress by this constant movement.

Faults are formed when stresses reach a high level. Tectonic plate movement produces fault movements as well. The sharp shifting of the Earth’s crust at a fault line causes an earthquake.

The place where the earthquake starts is known as the epicenter. The epicenter of an earthquake often experiences the strongest shaking.

What Happens During an Earthquake?

If you question why do earthquakes happen? The answer lies in the constant movement of tectonic plates. Friction can cause these plates to move more slowly as they collide in fault zones, which can result in a long-term buildup of pressure.

Sections of the crust suddenly crack or shift, releasing the accumulated pressure in the form of seismic waves. It happens when the force of movement ultimately outweighs the resistance to movement. This earthquake, commonly referred to as a tectonic earthquake, is a natural phenomenon.

Various energy wave types are produced during an earthquake. The first waves to be noticed are called “P waves” or “primary waves.” These waves are compressional, pushing and pulling through fluids and rock.

The subsequent waves to be detected are “S waves” or “secondary waves.” These waves can go through the rock. Perpendicular to the direction of the wave, they move up and down or side to side.

P and S waves both generate Surface waves. They move throughout the surface of the Earth, so they do the most damage.

Surface waves can be divided into two types: Rayleigh waves, which roll like waves on the surface of oceans and lakes, and Love waves, which are faster and move the ground from side to side. These different types of waves play a major role in the question of what happens in an earthquake.

How Earthquakes Work?

The following three have been suggested as the primary forces influencing tectonic plate movement, and they also give the answer to the question of how earthquakes work.

Mantle convection currents: Warm mantle currents push and carry lithosphere plates along in a similar manner to a conveyor belt.

Ridge push: It is a newly formed plate at oceanic ridges that are warm. So they have a higher elevation than the colder and denser plate material.

Gravity plays a major role in the higher plate at the ridge so as to push away the lithosphere.

Slab pull: At subduction zones, older, colder plates fall because, as they cool, they become denser than the mantle under them. The cooler, sinking plate then drags the remainder of the warmer plate behind it.

5 Causes of Earthquakes

Although natural earthquakes are more frequent, earthquakes can also be caused by humans. There are 5 causes of earthquakesand those are:

  1. Volcanic eruptions

Volcanic eruptions are the main causes of the earthquake. Such earthquakes are common in regions with active volcanism. With the increased pressure of gases, the Earth’s crust undergoes specific movements as boiling lava attempts to penetrate the surface.

There can also be some disturbances due to lava moving beneath the Earth’s surface. So, the Earth is damaged by shockwaves. These earthquakes are not strong, and their range is limited. However, there have been a few instances where volcanic earthquakes have caused devastation and killed thousands of people.

  1. Geological faults

When plates slide away from their original plane, this is referred to be a geological fault, and it can be of the horizontal or vertical plane. These planes do not emerge immediately but rather gradually through time.

Geological forces have an impact and cause these faults. Rocks fracture due to plate movement, which releases a lot of energy. An earthquake of this kind can be devastating.

  1. Tectonic movements

Multiple plates are found on the surface of the Earth. So, Earth’s crust is impacted by the continuous movement of these plates. These movements are classified into destructive, constructive, and conservative.

The separation of two plates, which causes small earthquakes, is constructive. Destructive plate boundaries are created when two plates move in the same direction and clash. Conservative plates are passing by two or more plates of crust. The intensity of these kinds of earthquakes varies.

  1. Man-made

The modification of nature by humans might trigger earthquakes. Earthquakes can be caused by the disruption of the crustal balance caused by the heavy storage of water in dams.

The tectonic plate alignment can be shifted by nuclear bombing, which can cause certain types of shockwaves to travel across the surface of the Earth. Mining can also result in small Earthquakes due to the removal of rocks from different areas.

  1. Minor causes

Minor events like avalanches, landslides, the collapse of large rocks, etc., can also send small shockwaves. The moving of plates under the crust is caused by the contraction and expansion of gases beneath the Earth’s surface.

Changes in rock strata within the Earth’s crust result in plutonic earthquakes. These all cause small earthquakes, but they may occasionally lead to moderate earthquakes.

How are Earthquakes formed?

The elastic rebound theory offers some answers to how earthquake happen. It says that in some circumstances, energy is stored in a rock that is being bent by tectonic pressures until the energy in the rock surpasses the bonding strengths between minerals and the rock breaks.

When a rock cracks, it suddenly returns to its original shape, and the rapidly released force causes the crust to shift. With this, a new fault is created.

You can use the example of a flexible plastic rod that has been bent to the point of breaking as an example. When it breaks, the energy that curved its two ends is released, and they immediately return to their original positions as straight lines. Most earthquakes last a few minutes, with displacement along the fault zone usually ranging from 1 to 7 meters.

According to another theory put forth by some geologists who work on the question of how does an earthquake happen? The deeper earthquakes are the result of mineral changes occurring in cold subducted plates that enter the hotter mantle.

Effects of Earthquake

Here are a few of the main effects of earthquake:

  1. Ground shaking

When an earthquake happens, the energy released produces seismic waves that cause the ground to shake. The magnitude of the earthquake, the distance from the epicenter, and the local geology are only a few examples of factors that can affect the shaking’s severity. The shaking gets stronger in areas around the epicenter, which can seriously harm buildings and infrastructure.

  1. Damage to Man-Made structures

The damage that earthquakes can do to buildings, bridges, roads, and other man-made structures is one of the effects of an earthquake that is most visible. Particularly if the buildings are not built or designed to resist seismic activity, the shaking may cause structural failure, collapse, and significant damage.

The standard of construction, compliance with building rules, and distance from the epicenter are just a few examples of the factors that affect the severity of the damage.

  1. Fires and hazardous chemical leaks

Earthquakes can result in fires and hazardous chemical leaks, and other secondary hazards. The shaking has the potential to disrupt infrastructure, burst gas pipelines, harm electrical systems that can lead to fire accidents.

Industrial facilities that keep dangerous chemicals may get leaked during an earthquake, harming both human health and the environment. These extra impacts can increase the effects of an earthquake and make rescue and recovery activities more challenging.

  1. Tsunamis

Underwater earthquakes can cause tsunamis, especially when they take place near tectonic plate borders. These enormous ocean waves have a great range and can reach coastal communities, where they can cause catastrophic floods.

  1. Landslides and avalanches

Earthquakes can cause landslides and avalanches in regions with unstable terrain or steep slopes. Rocks, Earth, and other debris can flow downhill with the shaking and can destabilize slopes.

Landslides can bury entire communities, destroy buildings, block highways, and cause other casualties. They also make it difficult for rescue and relief efforts to reach victims.

Earthquake detection

An earthquake’s seismic waves cause ground motions, which are recorded by seismograms. The measurement device used to generate a seismogram is known as a seismograph or seismometer.

The basis of almost all seismometers is the concept of inertia, which states that a suspended mass has a tendency to remain stable when the Earth is moving.

Seismometers enable the detection and measurement of earthquakes by turning seismic wave vibrations into electrical signals. It can then be shown as seismograms on a computer screen. So, the answer for how are earthquakes detected is seismometers.

Final thoughts

Here all about earthquakes are explained in detail and in a more simple way. Understanding why earthquake happens, the working of earthquakes, and also its causes and effects is crucial to defend yourself during an earthquake.

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