Earthquake: important points regarding earthquake


The surface of the Earth is made up of tectonic plates that lie beneath both the land and oceans of our planet. The movements of these plates can build mountains or cause volcanoes to erupt. The clash of these plates can also cause violent earthquakes, where Earth’s surface shakes. Earthquakes are more common in some parts of the world than others, because some places, like California, sit on top of the meeting point, or fault, of two plates. When those plates scrape against each other and cause an earthquake, the results can be deadly and devastating.

Important points

✓It refers to the vibration of the Earth's surface caused by the endogenetic forces of Earth.Seismology is the special branch of
geology that deals with the study of
✓The magnitude of an earthquake; usualy
expressed by the Richter scale, is a measure
of the amplitude of seismic waves. The
moment magnitude of an earthquake is a
measure of the amount of energy released
an amount that can be estimated from
seismograph reading.
✓The plane of origin of earthquake is called focus. The place on the ground surface, which is perpendicular to the focus or hypocentre is called epicentre.
✓The waves generated by earthquake
are called seismic waves and they are
classified into 3 types such as

1. Primary Wave (P Waves) 

These are the waves of short wave length and high frequency. They are longitudinal waves and can travel through solid, liquid and gases.

2. Secondary Wave (S Waves)

These are the waves of short wave length and high frequency. They are transverse waves, which travel through all solid particles.

3. Surface Waves or Long Waves (L Waves) 

They are the waves o long wavelength,confined to the skin of the Earth's crust. It causes most of the earthquake's.

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