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Seismicity of South Asia

Seismicity is defined as the distribution of seismic activity in time, location, magnitude & depth during the historical & recent instrumented period. Studies of seismicity are of great importance to understand the dynamic behaviour of the earth and is useful to determine the earthquake hazard in a specific region. Earthquakes are known to have occurred in the region of the Indian subcontinent from ancient times. Brief references are made to the seismic phenomena during the medieval period but it is not until the start of the colonial era from when clearer records of earthquakes emerge. Though incomplete in some respects, these provide a good overall summary of the distribution of earthquakes in the last 200 years. Most of the activity, including many "great" earthquakes have occurred in the northern subcontinent and in the Andaman & Nicobar Archipelago. The southern peninsula has suffered damaging earthquakes but less frequently as in the north.


Seismicity of India

Andaman Islands
Andhra Pradesh
Arunachal Pradesh
Assam
Bihar
Chandigarh
Chhattisgarh

Delhi
Goa
Gujarat
Haryana

Himachal Pradesh
Jharkhand
Jammu & Kashmir
Karnataka
Kerala

Lakshadweep Islands
Madhya Pradesh
Maharashtra
Manipur

Meghalaya
Mizoram

Nagaland
Nicobar Islands
Orissa
Punjab
Rajasthan
Sikkim
Tamil Nadu & Puducherry
Tripura

Uttarakhand (Uttaranchal)
Uttar Pradesh
West Bengal


Why do earthquakes happen here?
The Indian subcontinent lies upon the Indian Plate. This plate is moving northward at about 5 centimetres per year and in doing so, collides with the Eurasian Plate. Upon the Eurasian Plate lie the Tibet plateau & central Asia. Due to this mammoth collision, the Himalayas are thrust higher and very many earthquakes are generated in the process. This is the cause of earthquakes from the Himalayas to the Arakan Yoma. The same process, though involving the Indian Plate and the Burmese Micro-plate results in earthquakes in the Andaman & Nicobar Islands. Sometimes earthquakes of different magnitudes occur within the Indian Plate, in the peninsula and in adjoining parts of the Arabian Sea or the Bay of Bengal. These arise due to localized systems of forces in the crust sometimes associated with ancient geological structures such as in the Rann of Kachchh.

Inter-Plate Earthquakes (Plate boundary Earthquakes)

Most earthquakes occur along narrow zones that follow the edges of tectonic plates. These events are known as "Inter-Plate" or "Plate Boundary" earthquakes. These earthquakes are the direct result of the interaction between two or more tectonic plates. There are two prominent bands of Inter-Plate earthquakes. One stretches from the western Mediterranean, covering southern Europe and north Africa, extending through the Middle East and terminating in the Himalayas. The second band forms a circle around the Pacific Rim, including Kamchatka in Russa, Japan, the Philippines, Indonesia, the South Pacific island nations and New Zealand in the west. In the east it includes, Alaska, California and the Pacific North-west in the U.S., western Canada, Central America and the South American countries of Colombia, Ecuador, Peru and Chile. This circum Pacific belt is also often referred to as the "Ring of Fire".

Intra-Plate Earthquakes (Mid Plate Earthquakes)
Sometimes earthquakes occur far away from plate boundaries. These earthquakes are very infrequent but are capable of releasing just as much energy in a single earthquake as an earthquake of similar size along at plate boundary. These arise due to localized systems of forces in the crust sometimes associated with ancient geological structures such as in the Rann of Kachchh.  Seismic activity of this nature contributes 1% of the annual seismic energy release globally. All earthquakes in peninsula India falls within this category. Mid-plate earthquakes have also occurred in the central Indian Ocean, in the central & eastern United States, eastern Canada, Brazil, northern Europe, Australia, Hawaii and western parts of the African continent.

Page Updated: 21 Feb 2008 | Website Disclaimer

Amateur Seismic Centre, Pune,