Earthquakes occur in geologically active areas, such as mid-oceanic ridges and mountain-building regions. The zones where earthquakes occur frequently are known as ”Seismic belts”. The principal seismic belts on the earth’s surface are as follow:
- Circum Pacific Belt: This belt encircles the Pacific ocean and more or less overlaps the belt of young fold mountains and the zone of active volcanoes. About 80 % of the world’s earthquakes occur in the ”CircumPacific Belt”.
- Alpine Himalayan Belt: This belt starts from the East Indies and passes through the Himalayan foot-hill region to the Alpine mountain arcs of Europe. Two continental plates are in collision at the Himalaya mountains (the Indo-Australian and Eurasian plates), which began 52 million years ago. As both continental plates have the same low density, subduction is not possible. Instead, the plates have ‘crumpled’, creating enormous tectonic uplift in the form of the Himalaya and Tibetan Plateau. Collision zones are cut by huge thrusts that generate shallow, high magnitude earthquakes such as in Kashmir in 2005 and Nepal in 2015.
- Rift Valley regions: In India earthquakes frequently occur along the foot-hill zone of the Himalayas, starting from Kashmir in the west to Assam in the east. After 1819, 15 very destructive earthquakes have occurred in India.