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Earthquakes – Definition, Occurrence, Effects, Examples

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  • Last Updated : 15 Jun, 2022
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An earthquake is defined as a sudden release of energy in the earth’s crust that causes the earth’s surface to tremble. Seismic waves are produced as a result. The type and severity of an earthquake are determined by seismic activity in the area. Earthquakes are caused by sudden tectonic shifts in the earth’s crust. Orogeny occurs when tectonic plates collide, resulting in earthquakes and volcanoes. Vibrations spread in all directions as a result of these disruptions. As these plates move with respect to one another, tension builds up, which fractures by releasing stored energy in the form of shock waves.

Seismic waves are vibrations produced by earthquakes as they move through the Earth, which are recorded on seismographs. The hypocenter is the location beneath the earth’s surface where the earthquake begins, whereas the epicentre is directly above it.

Magnitude of Earthquakes

An earthquake’s magnitude is a numerical scale that measures the amount of seismic energy released by it. Magnitude is the most commonly used measure to quantify the total strength or size of an earthquake. An earthquake’s magnitude is stated in decimal fractions and whole numbers. A 5.3 magnitude earthquake, for example, is regarded as mild, whereas a 6.3 magnitude earthquake is deemed powerful. Due to the logarithmic basis of scale, each whole number increase in magnitude corresponds to a tenfold increase in observed amplitude on a seismograph.

In modern times, scientists and engineers utilise a variety of magnitude scales to estimate the relative size of an earthquake. An earthquake magnitude scale has no upper or lower bounds.

Earthquake Frequency

The frequency with which a certain magnitude earthquake occurs is commonly defined by an earthquake. On average, an earthquake of magnitude 2 or less occurs several hundred times per day around the planet. Every month, a large earthquake with a magnitude of 7.0 to 7.9 occurs somewhere in the world. An earthquake, on the other hand, happens once a year and has a magnitude of 8.0 or greater.

Occurrence of Earthquake

Earthquakes are triggered by abrupt tectonic upheavals in the earth’s crust. When tectonic plates contact, orogeny develops, resulting in earthquakes and volcanoes. As a result of these disturbances, vibrations spread in all directions. Tension is created when the plates move in respect to one another, which causes the plates to fracture by releasing the stored energy in the form of shock waves. This causes energy to be released, which travels in the form of energy waves in all directions. The epicentre, also known as the hypocenter, is the place at which the energy of an earthquake is released. On the earth’s surface, the epicentre is the point directly above the focus. It should be your first stop.

As a result, earthquakes are often generated by the breaking of underlying rock along a fault line. This quick release of energy generates seismic waves, causing the ground to tremble. When two rocks or plates meet, they cling to one another in a specific way. An earthquake occurs when the rocks crack.

Effects of Earthquake

  1. Earthquakes cause land shaking, surface faulting, ground collapse, and, less frequently, tsunamis.
  2. Human and animal death
  3. Several structures, lakes, and bridges have been destroyed.
  4. Tsunamis, landslides, and flooding

Sample Questions

Question 1: Where do earthquakes occur?


An earthquake can happen anywhere on the planet, but it usually happens near tectonic plates with active faults.

Question 2: What is a seismograph?


The seismograph is an instrument used to measure and record earthquake details such as force, duration, and so on.

Question 3: What is an earthquake zone?


An earthquake zone is the area on the earth’s surface where the bulk of earthquakes occur. It is often referred to as the seismic zone or the earthquake belts.

Question 4: Where do earthquakes occur most frequently?


The Earth’s uppermost layer is made up of multiple tectonic plates that either slide towards, away from, or under each other. Severe earthquakes typically occur along tectonic plate borders. The west coasts of North and South America, Indonesia, Japan, Central Asia, and sections of China and Turkey were all commonly affected by the earthquake.

Question 5: Why is the moment magnitude earthquake scale more popular?


The moment magnitude scale, abbreviated as Mw, is chosen over the Richter scale because it provides more precise measurements for a wider range of earthquake sizes and is applicable globally. This scale calculates earthquake size based on seismic movement rather than the amplitude of seismic waves measured by a seismograph. The only credible scale capable of measuring the greatest and most damaging earthquakes is the moment magnitude scale.

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