Hazard-specific
Hazard-specific — earthquakes · Himalayan seismicity
12 min read · Updated 2026-05-25
What is an earthquake?
An earthquake is the release of accumulated tectonic stress along a fault, beginning at a focus underground and felt most strongly at the epicentre above it. India is exposed because the Indian Plate drives north into Eurasia at about 4.5 centimetres a year: 59 per cent of the landmass lies in Seismic Zones III to V, and a 700-kilometre Central Seismic Gap remains unruptured.
The story
It is 25 April 2015, Saturday, 11:56 am local time. 80 km northwest of Kathmandu, the Indian Plate, drifting north at 4.5 cm/year, lurches under the Eurasian Plate along the Main Frontal Thrust. A magnitude 7.8 earthquake — the largest in Nepal since 1934 — rips a 150-km-long rupture. 9,000 dead in Nepal. Across the border in Bihar, UP, West Bengal, 78 Indians die. Mount Everest base camp is hit by avalanche; 22 climbers die. The Dharahara tower collapses on live TV.
For Indian seismologists, this is not a black swan. It is the 5th great Himalayan earthquake of the last 200 years (1819 Kachchh, 1897 Shillong, 1905 Kangra, 1934 Bihar-Nepal, 1950 Assam-Tibet). Each of these released 100-1000 years of accumulated stress. Between Dehradun and Kathmandu, geologists believe a M8+ "central seismic gap" earthquake is overdue — possibly within the lifetime of today's UPSC candidates.
What stands between the next great Himalayan quake and a catastrophe is the National Disaster Management Authority's earthquake guidelines (2007), IS 1893 building code, the Bhuj 2001 reconstruction lessons, and a network of seismic observatories run by the National Centre for Seismology. This unit covers the geology, the geography, the institutional response, and the still-unfinished business.
Why this matters for UPSC
Earthquake questions are annually tested in Prelims (seismic zones, Bhuj date, magnitude scales). Mains demands you connect plate tectonics + seismic zoning + building codes + Bhuj-Nepal lessons. The 2023 Joshimath subsidence and the looming "central seismic gap" make this an Interview hot topic. The fact that 59% of India's landmass is in Zones III-V means it is also a Mains GS-I (geophysical phenomena) crossover.