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    What Is The Science Behind An Earthquake?

    By sumit saini
    4 Nov'22  5 min read
    What Is The Science Behind An Earthquake?
    Synopsis

    Earthquake is one of the most devastating disasters. Many of us don't know the exact science behind the occurrence of the earthquakes. In this article we discuss the science behind the earthquake, reasons for frequent earthquakes in particular regions and how to minimise the risk in such regions. Read on to know in detail.

    What Is The Science Behind An Earthquake?
    Synopsis

    Earthquake is one of the most devastating disasters. Many of us don't know the exact science behind the occurrence of the earthquakes. In this article we discuss the science behind the earthquake, reasons for frequent earthquakes in particular regions and how to minimise the risk in such regions. Read on to know in detail.

    What Is An Earthquake

    An earthquake is caused when the tectonic plates collide and there is a slip in the plates. In the lithosphere, the tectonic plates are in slow motion, but sometimes they get stuck at their edges due to friction. Due to friction, the stress on the edges becomes high which results in an earthquake. When the earthquake occurs, it releases energy in the form of waves that travel through the earth's crust and cause the shaking of the earth. The waves emerging from the earth are known as seismic waves.

    Earthquakes occur most often along geologic fault lines and narrow zones where rock masses move against each other. The major fault lines of the world are located at the joints of the huge tectonic plates that make up Earth’s crust.

    Hypocentre is known as the location below the earth’s surface where the earthquake starts and epicentre is the location which is directly above it on the surface of the earth

    Below images show the movements of earth's plates and the fault lines of tectonic plates across the globe respectively.

    Fig. Movements of Earth's Plates

    Fig. Tectonic Fault lines across Globe

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    Causes of Earthquakes

    As discussed above, major earthquakes occur along the margins of the tectonic plates.

    The most important earthquake belt in the world is the Circum-Pacific Belt which is considered as the most active region for earthquakes. The Circum-Pacific Belt affects the regions around the Pacific Ocean which includes the part of countries like New Zealand, New Guinea, Japan, Alaska, Aleutian Islands and the western coasts of North and South America.

    Along with earthquakes, the Circum-Pacific Belt is associated with volcanic activity also, hence it is popularly known as the “Pacific Ring of Fire.”

    Multiple reasons for the occurrence of earthquakes are as follows :

    Tectonics

    Due to the movement of the tectonic plates, the collision takes place at the interface of fault lines. This results in the shaking of the earth’s crust and hence leading to the occurrence of an earthquake. Tectonically induced earthquakes are most prominent among all types of earthquakes, hence they are observed frequently. In the case of India,Himalayan region is prone to tectonically induced earthquakes as Indian and Eurasian Plates collide more often.

    Volcanism

    Apart from the tectonically indices, there is an Earthquake due to volcanic activity and it is called a volcanic earthquake. In the process of Volcanism, the disturbance is the result of a sudden slip of rock masses adjacent to the volcano and the consequent release of elastic strain energy which leads to Earthquake. Earthquakes associated with volcanic eruptions are most prominent along the Pacific ring of Fire region in the Pacific ocean.

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    Man Made Reasons

    Human activities are contributing to the occurrence of earthquakes. Activities like

    injection of fluids into deep wells, underground nuclear explosions, the excavation of mines, and the filling of large reservoirs leads to unusual movement of tectonic plates due to heavy load.

    For example, underground nuclear explosions generate seismic waves through the body of the Earth that are of much larger amplitude than the waves of natural earthquakes. Hence man made reasons for earthquakes are no less devastating for humankind.

    Seismic waves

    Intensity of the Earthquakes heavily depends upon the seismic waves. To understand the Earthquakes, we need to understand the seismic waves.

    Seismic waves generated by an earthquake are commonly classified into three main types and in two groups which are:

    1. P (or primary) and S (or secondary) waves which propagate within the body of the Earth.

    2. Love and Rayleigh waves which propagates along earth's surface.

    The P seismic waves travel at the highest speeds in an elastic manner. P waves are longitudinal in nature and can be transmitted by both solid and liquid materials in the Earth’s interior.

    Along the motion of P waves, the particles of the medium vibrate alternately in a compressed and expanded manner.

    The S wave is a slower type of body wave which travels only through solid medium. The motion of particles along the S waves is transverse to the direction of travel.

    Love and Rayleigh waves are surface waves which are more destructive in nature and moves behind the “P” and “S” waves.

    Effects Of Earthquakes

    Earthquakes have various effects on the earth including changes in geologic features, damage to man-made structures, and impact on human and animal life. Significant damage to the buildings, bridges, pipelines, railways and other structures are the consequence of the earthquakes. The earthquakes originate under the ocean bottom, so some of the effects are often observed along the margins of oceans.

    Due to movements of the tectonic plates under the seabed, Tsunami is observed which causes the sudden raising or lowering of a large body of water. Tsunami waves do a great deal of damage in low-lying coastal areas.

    How are earthquakes recorded

    Earthquakes are recorded with the help of seismographs. Seismographs is a device which is attached to the spring and when an earthquake comes, the strain in the spring increases. The spring is attached to the device which measures the strain in the spring and calculates the intensity of the earthquake. The power of an earthquake is expressed in terms of a magnitude on a scale called the Richter scale.

    Protection Against Earthquakes

    Earthquakes cannot be predicted and they are highly destructive in nature. Therefore it is important that we take necessary precautions. People living in seismic zones and the areas prone to regular earthquakes have to prepare themselves. They must know some of the basic techniques to save themselves.

    Some measure which can minimise the loss due to Earthquakes are:

    • Buildings in these zones should be designed in a manner that they can withstand major tremors.

    • It is advisable to make the structure simple so that it is ‘Earthquake Safe’.

    • Consult qualified architects and structural engineers.

    • Cupboards and shelves must be fixed to the walls, so that they do not fall easily.

    • Some buildings may catch fire due to an earthquake, it is necessary that all buildings have fire extinguishing equipment in working order.

    • If you are at home during the earthquake and not able to come out, then take shelter under a table until the earthquake stops. If you are outdoors then go to an open space which is away from buildings and trees.

    These measures can help to an extent. Better solution can be early detection of earthquakes which can alert the people. Research is underway to successfully get the early warning of an earthquake.

    • Nature
    • Applied and interdisciplinary physics
    • Classical mechanics
    • Mechanics
    • Physical phenomena
    • Mechanical engineering
    • Wave
    • Continuum mechanics
    • Solid mechanics
    • Geology

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