What Is An Earthquake? What Causes It And How To Measure It Through Richter Scale?

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What Is an Earthquake?
Even though the Earth has a pretty solid surface, the interior is extremely active. There are four basic layers: a solid crust, a hot, nearly solid mantle, a liquid outer core and a solid inner core. When there is an intense shaking of the Earth's surface, there are caused by moments in the Earth's outermost layer.

Why Do Earthquakes Take Place?
An earthquake occurs when two blocks of the earth suddenly slip past one another and the surface where the slip happens is called the fault plane or fault. The tectonic plates are always moving slowly but they can get stuck at their edges owing to friction. When the stress on the edge overcomes the friction, then there is an earthquake that releases energy in waves that travel through the earth's crust and cause shaking that one feels.

When an earthquake starts, the location below the earth's surface is known as the hypocenter and the location directly above it on the surface of the earth is called the epicentre. Also, at times an earthquake has foreshocks.

The largest, main earthquake is called the mainshock. Mainshocks always have aftershocks that follow, which are basically smaller earthquakes that occur later in the same place as the mainshocks. This can continue for days, weeks, months and even years depending on the size of the mainshock.

How To Measure An Earthquake Through Richter Scale?
Richter scale is the first and widely used method when it comes to measuring an earthquake and it was first developed by Charles F Richter in 1934. It is basically a formula that was developed based on the amplitude of the largest wave recorded on a specific type of seismometer and the distance between the seismometer and the earthquake.

According to the Oxford Dictionary, it is a numerical scale for expressing the magnitude of an earthquake on the basis of seismograph oscillations. The more destructive earthquakes typically have magnitudes between about 5.5 and 8.9; it is a logarithmic scale and a difference of one represents an approximate thirtyfold difference in magnitude.

Under the Ministry of Earth Sciences (MoES), National Centre for Seismology (NCS) maintains a nationwide seismological network comprising 115 seismic stations to monitor earthquake activity pan India and around the nation. The whole country has been divided into four zones viz. zone V, IV, III and II according to the seismic zoning map of India prepared by the Bureau of Indian Standards (BIS) based on the historical seismicity and strong ground motions. Out of these zones, Zone V exhibits the highest seismic risk and zone II has the least, mentioned in Press Information Bureau.