Geography Topic: Important Points about Earthquakes for Competitive Exams

Geography-Earthquakes

It refers to the vibration of the Earth's surface caused by the endogenetic forces of Earth. The magnitude or intensity of energy released by an earthquake is measured by the Richter Scale, whereas the damage caused is measured by modified Mercalli Intensity Scale. The place of origin of earthquake is called focus. The place on the ground surface, which is perpendicular to the focus or hypocentre is called epicentre. Seismology is the special branch of geology that deals with the study of earthquake.

The waves generated by earthquake are called seismic waves and they are classified into three types such as

• Primary Waves( P Waves): These are the waves of short wavelength and high frequency. They are longitudinal waves and can travel through solid liquid and gases.
• 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.
• Surface Waves or Long Waves ( L Waves): They are the waves of long wavelength, confined to the skin of the Earth's crust. It causes most of the earthquake's structural damage.

The Earthquake Zones, in India:

The Indian plate is moving from South to North at the speed of 5 cm/year and the Eurasian Plate is static on its own position, so there is a collision between Indian Plate and Eurasian Plates. Due to this collision, the earthquakes occurs in the Himalayan regions of India. The collision also results in the increase of the height of Himalayas at the speed of 1 cm/year. The second most important earthquake zone is Parallel to Punjab and Rann of Kutch. It occurs due to the movement between the transform boundaries of Eurasian and Indian Plates. Earthquakes occur in Asom, Arunachal Pradesh, Nagaland, Tripura, Mizoram, Andaman and Nicobar Islands, Jammu and Kashmir, the North-Western region of Uttar Pradesh and the Northern region of Bihar etc.

Distribution of Earthquakes:

Most of the world earthquake occur in

• The zones of young fold mountain
• The zones of folding and faulting
• The zones of junction of continental and oceanic margin
• The zone of active volcanoes
• Along different plate boundaries

The Traditional Zones of Earthquakes

• Circum Pacific belt
• Mid Continental belt
• Mid Atlantic belt