Earthquake; Definition, Causes, Types, Body Waves

Earthquake is a phenomenon that occurs in nature and is characterized by a brief shaking or trembling of the earth. It happens as a result of disruptions that take place deep inside the earth’s crust or as a result of these disturbances. Deep below the earth, where they cannot be seen from the surface, earthquakes frequently occur. On the surface of the planet, large earthquakes can happen at any time and can be devastating.

Causes of Earthquakes

1. Earthquakes occur as a result of the release of energy. A fault is when energy is released. A fault is a distinct breach in the rocks of the crust. A fault tends to cause the movement of rocks in opposite directions. They are locked together by friction as they are compressed by the rock strata underneath.
2. The friction is eventually overcome by their propensity to drift apart. The bricks finally distort as a result, sliding abruptly past one another. Energy is released as a result, and energy waves spread out in all directions.
3. The inner core, outer core, mantle, and crust are the four main layers of the earth. Our planet’s surface is covered by a thin layer of skin made up of the crust and the top of the mantle.
4. The plate boundaries are the margins of the seven big lithospheric plates and several smaller plates that make up the Earth’s crust. These plates move past each other, apart, or in a direction that is either convergent or divergent (a transform boundary).
5. The majority of earthquakes in the world happen on the numerous faults that make up the plate borders. A abrupt release of stress along these fractures in the earth’s crust is what causes earthquakes.
6. Along the plate borders are where the majority of earthquakes occur. Because earthquakes occur there so frequently, the area is known as the “ring of fire” and is considered to be a bit more vulnerable.
7. The pressure in the geological strata on either side of a fault steadily increases due to the ongoing movement of tectonic plates. It continues until the level of stress is high enough to cause a quick, jerky movement to be released.

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Types of Earthquakes

Tectonic Earthquakes

Tectonic plates are the loose, fractured land chunks that make up the earth’s crust. These plates have the capacity to move gradually and slowly. These plates travel in a variety of directions, including toward one another, away from one another, sliding past one another, and colliding with one another. When 2 moving tectonic plates cross each other, it causes a tremendous tremor. A tectonic earthquake is this sort of earthquake.

Volcanic Earthquakes

Volcanic earthquakes are less frequent than tectonic earthquakes. Usually, they occur prior to or following an eruption. Long-period volcanic earthquakes and volcano-tectonic earthquakes are the two types of volcanic earthquakes. A volcanic eruption is generally followed by volcano-tectonic earthquakes. Magma bursts from the earth’s crust during an earthquake, creating a void in its wake. After a magma eruption, the empty area needs to be filled. Rocks migrate in the direction of the empty area to fill it, causing powerful earthquakes.

Explosion Earthquakes

Nuclear explosions are the cause of this. They are essentially earthquakes that are caused by humans and are the biggest consequence of nuclear war today. Numerous small towns and villages were completely destroyed as a result of the United States’ nuclear experiments in the 1930s.

Collapse Earthquakes

These earthquakes are often smaller and most frequently happen close to underground mines. Mine bursts is another name for them. The pressure that builds up inside the rocks causes earthquakes that collapse. This type of earthquake causes the roof of the mine to fall, which causes more tremors. In small towns with underground mines, collapse earthquakes are common.

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Earthquakes Body Waves

P-waves

The primary wave, also known as a pressure wave or P-wave, is the earliest kind of body wave. This particular seismic body wave has the fastest ground velocities. P-waves move similarly to sound waves because they are a longitudinal compressional waveform. They move through the ground by pushing (compressing) and pulling (expanding) it alternatively as they spread out.

Both solid rock and liquid substances, such as volcanic magma or oceans, can be traversed by P-waves. Depending on the substance they are travelling through, their speed can range from 1,600 to 8,000 m/s. They are the first kind of wave to be felt and recorded on a seismograph during an earthquake due to their speed.

S-waves

The second kind of body wave is referred to as an S-wave and is also known as a secondary wave, shear wave, or shaking wave. The ground is sheared sideways by S-waves, a transverse waveform that travels perpendicular to the direction of motion.

Depending on their polarization and travel direction, S-waves have various effects on the ground. In relation to the direction they are flowing, horizontally polarized S-waves will cause the earth to shift from side to side (left and right). S-waves that are vertically polarized will cause the ground to rise and fall in relation to the direction of movement. S-waves cannot travel across liquids like lakes and oceans because it is impossible to twist or shear a liquid.

S-waves typically move at velocities between 900 to 4,500 m/s and are 40 percent slower than P-waves in any given material. During an earthquake, these waves are the second to be recorded on a seismograph. S-waves can have stronger amplitudes and can result in higher amounts of ground shaking than P-waves, despite their slower speed. This makes them frequently more damaging than P-waves.

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What are the Effects of Earthquakes?

Ground Shaking

The ground vibrating during an earthquake is referred to as “ground shaking.” Body waves and surface waves create ground trembling. As a general rule, ground shaking gets worse as its magnitude grows and gets better as its distance from the fault that caused it grows.

Surface Faulting

Surface faulting, which can be strike-slip, normal, or reverse, is the difference in movement of two sides of a crack at the Earth’s surface (or thrust). Strike-slip faulting and the other two types of faulting can coexist. Surface faulting, as the term is used here, refers to differential movements caused by deep-seated forces in the Earth, the slow movement of sedimentary deposits toward the Gulf of Mexico, and faulting associated with salt domes, even though displacements of this kind can result from landslides and other shallow processes.

Ground Rupture

Another significant impact of earthquakes is ground rupture, which happens when the movement of the earthquake along a fault actually splits the Earth’s surface. Although active ground rupture is very uncommon, it has happened in California. For instance, after the 1906 earthquake, fences around Pt. Reyes were moved up to 7 meters. Additionally, a fault scarp up to 8 meters high ruptured the ground at Lone Pine during the 1872 Owens Valley earthquake. Pipelines, tunnels, aqueducts, railway lines, highways, and airport runways that intersect an active rupture zone can easily be destroyed or seriously damaged. Rupture causes issues for humans by, well, rupturing things.

Tsunamis

Water waves known as tsunamis are brought on by the abrupt vertical shift of a sizable portion of the ocean floor following an underwater earthquake. Tidal waves are frequently used to refer to tsunamis, but this word is inaccurate. Tsunamis are not brought on by the Moon and Sun’s tidal action, in contrast to normal ocean tides. In the deep ocean, a tsunami’s height is normally around one foot, but the gap between wave crests can be extraordinarily wide—more than sixty miles. The tsunami moves more slowly as the ocean depth gets shallower. Tsunami speeds can exceed 430 miles per hour in the middle of the Pacific Ocean, when the sea depth reaches three miles.

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