Earthquake and Tsunami in geography upsc

Table of contents:

• Earthquake Definition
• Wave
• Reasons for Earthquake
• Characteristics of the earthquake
• Types of Earthquakes
• Earthquake Prediction
• Earthquake preparations
• Tsunami

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Earthquake means is shaking of the earth. It is caused due to the release of energy which is generally in the form of a wave that travels in all directions.

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Wave

Wave transfers energy from one location to another location.

• Some wave needs a medium to transfer energy. For example, sound waves, earthquake waves, etc.
• Some wave does not need a medium to transfer energy. For example, electromagnetic waves such as lights.

Generally, the following are two types of wave:
Longitudinal wave:

• Transfer of energy in the same direction as the wave.

Parallel wave:

• Displacement of the medium in parallel to the direction of the wave.

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Earthquake reasons

It is because of the sharp break in the crust or lithospheric plates.

Plate tectonic theory explains the origin of the earthquake:

There are three types of boundaries in plate tectonic motion:

• Divergence
• Transverse
• Convergence.

Divergence boundary:

• Two plate moves in the opposite direction create fault, volcanoes, and rupture. Minor Earthquakes may generate a shallow origin.
• Examples, mid-ocean ridge in the Atlantic and Indian ocean.

Transverse boundary:

• Fault in the crust may occur in a transverse boundary with a major earthquake.
• For example, an earthquake in the USA.

Convergence boundary:

• A large number of earthquakes are arisen on convergence boundaries of the ocean to the ocean, ocean to continental, and continental to continental convergence boundary.
• Nearly 70 % of the total earthquake is found in the Pacific ring of fire region due to ocean and continental convergence.

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Characteristics of Earthquake

Focus: 

The place where energy is released; this point is called the focus of the earthquake.

Epicenter: 
The nearest point on the earth's surface from focus where the wave is recorded first is called the epicenter of the earthquake.

Earthquake wave:
All earthquakes are originated from the lithosphere ( from 10 to 200km depth. ,).

Two types of earthquakes wave:

• Body wave
• Surface wave.

Body wave:
The energy generated at focus, it moves all the direction of the body of the earth.
Surface wave:
The body wave interacts with surface rock and generates a new type of wave, called surface rock.

Body wave:

• P wave or primary wave
• S wave or secondary wave

P wave:
Faster and first to arrive surface is called the primary wave.

S wave:
It causes the collapse of the earth's surface. It can travel only through solid material. It helps to understand the interior of the earth's surface.

Propagation of earthquake wave;

• P wave vibrates parallel to the direction of the wave. As a result, it creates a density difference in the material leads to stretching and squeezing of the materials. The p wave is the same as a sound wave; it travels in all mediums but the speed of the wave depends on the elasticity of the medium. High wave speed in less elastic materials. Wave speed highest in solid, medium in liquid, and lowest in gas medium.
• S wave and other wave vibrates perpendicular to wave direction, hence it creates troughs and crests in the material. S waves can not travel in the liquid and gaseous medium.

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Types of Earthquake:

The following are the five types of earthquakes based on the sources of origin.

• Tectonic earthquake
• Volcanic earthquake
• Collapse earthquake
• Explosion earthquake
• Reservoir-induced earthquake.

The tectonic earthquake is originated due to the sliding of rocks along with a fault plane.
Volcanic earthquakes are originated due to volcanic activities
collapse earthquake due to intense mining.
Explosive earthquake due to the explosion of chemical or nuclear activities.
The Reservoir earthquake is induced by the larger dam.

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Effects of Earthquake:

• Ground shaking
• Ground lurching
• Lands and Mudslide
• Soil liquidation
• Floods from Dam
• Avalanche
• Fire
• Structural collapse
• Human and economic losses.
• Tsunami

The greatest damage usually happens closest to the epicenter and the strength of the earthquake decrease away from the epicenter.

The earthquake can not be predicted by modern science, but the impact can be minimized through strong resilient infrastructure.

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Common earthquake prediction:

• Studying animal behaviors
• Fish in the ponds get agitated
• Snakes come out to the surface

Earthquake preparation:

• Preventive measure:
• Should have strong resilience infrastructure
• During earthquakes:
• Stay in safe spots such as under the kitchen counter, tables, or desk.
• Stay away from fireplaces, mirror areas around chimney, electric poles, etc

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Tsunami 

A tsunami is a large wave with a larger wavelength over larger water bodies such as the ocean which causes the larges scale of destruction in coastal areas.

• Tsunami wave speed is usually approximately 800 km per hour.
• Wavelength: it is the horizontal distance between two successive crests.
• Wavelength and speed of wave decrease with decreasing the water depth.

A tsunami can be caused by the following events if it happened in the ocean:

• Earthquakes
• Volcanic eruption,
• Meteorite drops,
• Landslide in oceans

Tsunami warning system:

• As of now, the earthquake can not be predicted, however, a tsunami can be predicted before 3 hours.
• The early warning system has been installed in the Indian ocean after the 2004 tsunami.

For Explanation, please watch the below videos:

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