India

India's seismic landscape is dominated by two fundamentally different earthquake environments. The Himalayan arc in the north, created by the ongoing collision of the Indian Plate with Asia, represents one of the world's most dangerous seismic zones, capable of generating great earthquakes exceeding magnitude 8.5. The Indian Plate interior — the ancient stable craton — is generally less seismic but has produced devastating intraplate earthquakes where ancient [[fault]] systems are reactivated by far-field stresses. The country is formally divided into five seismic zones (I through V), with Zone V encompassing the northeastern states, Jammu and Kashmir, Himachal Pradesh, Uttarakhand, and parts of Gujarat. The Andaman and Nicobar Islands lie at an active [[subduction-zone]] and are highly seismic.

India's seismic history includes some of the most catastrophic earthquakes of the 20th century. The 1905 Kangra earthquake (magnitude 7.8) killed over 19,000 people in the Punjab Himalaya. The 1934 Bihar-Nepal earthquake (magnitude 8.1) killed more than 10,000 in the Gangetic plains. The 1950 Assam earthquake (magnitude 8.6) remains one of the largest continental earthquakes ever recorded, triggering massive landslides and riverine floods. The 1993 Latur earthquake (magnitude 6.2) in Maharashtra exposed the hidden hazard of intraplate events, killing nearly 10,000 people in villages built of stone masonry. The 2001 Bhuj earthquake (magnitude 7.7) in Gujarat devastated the Kutch region, killing over 20,000 people and becoming a watershed event for Indian earthquake engineering and building codes. [[aftershock]] sequences from Indian Himalayan earthquakes can extend for years, complicating recovery efforts.

The tectonic framework of India reflects 50 million years of continental collision following the closure of the Tethys Ocean. The Indian Plate continues to move northward at roughly 45–50 millimetres per year relative to Asia, and while much of this motion is now accommodated within the thickened Tibetan crust, 15–20 millimetres per year is still taken up by active shortening across the Himalayan thrust belt. The Main Frontal Thrust (MFT) is the most active structure in the Indian Himalaya, and paleoseismic investigations show evidence of great prehistoric earthquakes exceeding magnitude 8.5 that ruptured the entire arc length of the fault. The Andaman Trench to the southeast is a fully active [[subduction-zone]] where the Indian Plate descends beneath the Sunda Plate, generating frequent moderate to large earthquakes and the occasional great tsunami-generating event, as seen in the 2004 earthquake. [[intensity]] maps from historical Indian earthquakes reveal the complex interaction between source, path, and local site conditions across the subcontinent's varied geology.