Earthquakes in India: causes, zones and landmark events

Detail

1. What causes earthquakes: the types

• Earthquake: the ground shakes suddenly when energy stored in rocks is released along a fault (a crack in the crust where blocks of rock move past each other).
• Tectonic earthquakes come from the movement of lithospheric plates (the large rigid slabs that make up the Earth's outer shell). They are the most destructive and cover the widest area.
• Other earthquakes are smaller and more local:

Type	Cause	Reach
Tectonic	Plates move and faults slip	Widespread, most destructive
Volcanic	Magma moves under a volcano	Local, near volcanoes
Collapse	Rock falls, landslides, roofs of mines falling in (mining subsidence: the ground sinking over old mines)	Very local
Reservoir-induced	Weight and water pressure of a large dam lake	Near the dam, e.g. Koyna

• Ancient knowledge: the NCERT Class 9 chapter shows that Indian scholars studied earthquakes long ago. Varahamihira (6th century CE) wrote about them in the Brihat Samhita.

2. Himalayan earthquakes: why the north shakes

• Plate movement:
• The Indian plate moves north-northeast. NCERT puts the speed at about 1 cm a year.

• Beyond NCERT: GPS (satellite positioning) measurements show about 4-5 cm a year. About 2 cm a year of this is absorbed as the Himalaya is squeezed and shortened.

• How stress builds:

• The Indian plate is locked (held fast by friction) against the Eurasian plate.
• The plate keeps pushing, so strain energy piles up in the rocks.

• When the rocks can take no more, they slip suddenly and the energy is released as an earthquake along the Himalayan arc.

• Most vulnerable areas: Jammu and Kashmir, Ladakh, Himachal Pradesh, Uttarakhand, Sikkim, the Darjeeling subdivision (West Bengal) and all seven northeastern states.

3. Great Himalayan earthquakes (landmark events)

Year	Event	Region	Key facts
1897	Shillong earthquake	Meghalaya plateau, Assam	One of the greatest quakes on record in India
1905	Kangra earthquake	Himachal Pradesh	A great quake in the western Himalaya
1934	Bihar-Nepal earthquake	North Bihar and Nepal	Very heavy damage in the Ganga plain
1950	Assam (Assam-Tibet) earthquake	Eastern Xizang (Tibet)-India border	M 8.6, one of the largest earthquakes in the world. 1,526 died, at least 780 of them in eastern Tibet. It caused sandblows, ground cracks and large landslides. A village slid into the Yarlung Zangbo (Brahmaputra) [4]
2005	Kashmir earthquake	Near Muzaffarabad (PoK)	M 7.6, over 80,000 dead
2015	Nepal (Gorkha) earthquake	Central Nepal	Damage spread into north India

• Magnitude (M): a number for the energy released at the source. Each whole step up means about 32 times more energy.
• 2005 Kashmir earthquake (NCERT Class 11's opening example):
• Date and size: 8 October 2005, M 7.6, near Muzaffarabad in Pakistan-occupied Kashmir (PoK).
• Toll: over 80,000 dead, with damage on both sides of the LoC (Line of Control).

• Aman Setu at Uri (J&K), the "peace bridge" across the LoC, was damaged.

• Central seismic gap: a stretch of the central Himalaya, roughly between the 1905 Kangra and 1934 Bihar-Nepal ruptures (covering Uttarakhand and western Nepal), that has not had a great quake for centuries.

• Strain has kept building there.
• So scientists fear a future great earthquake in this stretch.

4. Peninsular earthquakes: why the "stable" shield shakes

• Peninsular shield: the old, hard block of the Deccan plateau. It was long thought to be safe from earthquakes, yet it has had deadly ones.
• Two main clusters:
• Gujarat: the 1819 Rann of Kachchh quake, the 1956 Anjar quake and the 2001 Bhuj quake.

• Maharashtra: the 1967 Koyna quake and the 1993 Latur quake.

• Explanations:

• Bhima fault: a fault zone along the Bhima river (a tributary in the Krishna basin) near Latur and Osmanabad (Maharashtra). Energy released along this fault can cause quakes.
• Plate breaking: the Indian plate pushes against the locked Himalaya, so it may slowly be breaking up inside the shield, and stress is released along old weak lines.

5. Latur earthquake 1993

• Date and place: 30 September 1993, at Killari in Latur district, Maharashtra.
• Size: about M 6.2-6.4.
• Toll: about 10,000 dead.
• Why so many died (a moderate quake but a huge toll):
• The quake struck in the early morning, while people were asleep.
• Village houses had heavy stone walls and roofs held together with mud.

• These collapsed and buried the people inside.

• Lesson: buildings kill people, not the shaking itself. This led to the push for safe building codes in rural areas.

6. Bhuj earthquake 2001

• Date and place: 26 January 2001 (Republic Day), in Kachchh district, Gujarat.
• Size and toll: about M 7.7, about 20,000 dead (shown in NCERT Class 9, Fig. 2.5).
• Turning point in policy:
• Before Bhuj, India mostly reacted after a disaster with relief work.
• After Bhuj, it moved to a proactive approach: preparing, reducing risk and planning in advance.

• Gujarat passed the Gujarat State Disaster Management Act 2003, the first state law of its kind. It helped shape the national Disaster Management Act 2005.

• Kachchh had shaken before, in 1819 and in 1956 (Anjar). It is one of the most active parts of the Peninsula.

7. Reservoir-induced earthquakes: Koyna 1967

• Reservoir-induced seismicity (RIS): earthquakes started or made stronger by filling a large dam reservoir.
• How it happens:
• A huge mass of water adds load (weight) on the crust below.
• Water seeps down into cracks and raises pore pressure (the pressure of water inside rock cracks and pores).

• Higher pore pressure "unclamps" a fault that is already under stress. It slips, and an earthquake follows.

• Classic case: Koyna, 11 December 1967, about M 6.3, near the Koyna dam in Satara district, Maharashtra (Western Ghats).

• Concern today: the Tehri dam on the Bhagirathi in Uttarakhand sits in a highly seismic Himalayan zone. Experts worry both about RIS and about the dam's safety in a great quake.

8. Seismic zones of India

(a) NCERT's five damage-risk zones (Class 11, Fig. 6.2)

• The zones are based on an analysis of over 1,200 earthquakes by the National Geophysical Laboratory, GSI (Geological Survey of India), IMD (India Meteorological Department) and NIDM (National Institute of Disaster Management).

Zone	Areas
Very high damage risk	Northeastern states; areas north of Darbhanga and Araria in Bihar along the Nepal border; Uttarakhand; western Himachal around Dharamshala; Kashmir Valley; Kachchh (Gujarat)
High damage risk	Rest of J&K, Ladakh and Himachal; northern Punjab; eastern Haryana; Delhi; western Uttar Pradesh; northern Bihar
Moderate, low and very low	The rest of the country. The Deccan plateau is the safest

(b) BIS seismic zoning (the official building code)

• BIS (Bureau of Indian Standards) issues IS 1893 (Part 1), "Criteria for Earthquake Resistant Design of Structures". It includes the Seismic Zoning Map of India [2].
• In 2002, Zone I was merged into Zone II, which left four zones: II to V.
• Share of India's area by zone [3]:

Zone	Hazard	Share of area
V	Highest (most active)	about 11%
IV	High	about 18%
III	Moderate	about 30%
II	Low (least active)	the rest, about 41%

• Going by the recorded history of earthquakes, about 59% of India's land area, covering all states, is prone to earthquakes of different strengths [3].
• Zone V includes the whole northeast, parts of Kashmir, Himachal and Uttarakhand, north Bihar, Kachchh, and the Andaman and Nicobar Islands.
• Delhi is in Zone IV.

(c) The 2025 revision and its withdrawal

• A 2025 revised zonation created a new top category, Zone VI, and put the entire Himalayan arc in it.

• Only a small part of north-eastern Ladakh stayed in Zone V [2].

• This revision was withdrawn in March 2026. IS 1893 (Part 1): 2016 is again the current standard [2].

• After the Himalaya was rated high-risk, the government also started studies on site response (how local soil makes shaking stronger or weaker), fault mapping and regional source characterisation (finding which faults can produce quakes) [2].

Prelims Hooks

• The Bhima fault (Krishna basin) is linked to the Latur 1993 quake at Killari, Maharashtra.
• Koyna 1967 (M 6.3, Satara, Maharashtra) is the classic reservoir-induced earthquake.
• Bhuj 2001 (26 January, Kachchh, M 7.7) led to the Gujarat State Disaster Management Act 2003.
• The Assam 1950 quake (M 8.6, 15 August) is the largest in India's recorded history [4].
• Aman Setu (Uri, J&K) was damaged in the 2005 Kashmir earthquake, whose epicentre was near Muzaffarabad (PoK).
• BIS zones today: II, III, IV, V. Zone I was merged into II in 2002. Zone V covers about 11% of the area and Zone II the most [3].
• Delhi = Zone IV. The Andaman and Nicobar Islands = Zone V.
• Trap: the 2025 Zone VI map was withdrawn in March 2026, so IS 1893 (Part 1): 2016 still applies [2].
• Trap: the Deccan is the safest zone, but it is not quake-free (Latur, Koyna).
• Chronological order: Rann of Kachchh 1819 → Shillong 1897 → Kangra 1905 → Bihar-Nepal 1934 → Assam 1950 → Anjar 1956 → Koyna 1967 → Latur 1993 → Bhuj 2001 → Kashmir 2005 → Nepal 2015.

Mains Points

• Causes and distribution (GS-I):
• The Indian plate is locked against the Eurasian plate, so stress builds and the Himalayan arc and the northeast are the most quake-prone areas.
• The shield is not fully stable. Quakes there come from old faults (Bhima), from the plate slowly breaking, and from large reservoirs (Koyna).

• The central seismic gap points to a possible future great quake under densely populated Uttarakhand and the Ganga plain.

• Buildings decide the death toll (GS-III):

• Latur (M 6.2, about 10,000 dead) shows that weak stone houses, not magnitude alone, decide how many people die.

• Policy needs: enforce IS 1893, retrofit (strengthen) existing buildings, make rural houses safer, and do microzonation (detailed hazard maps at city level) for Zone IV and V cities such as Delhi.

• Policy turning point (GS-III):

• Bhuj 2001 moved India from relief after a disaster to prevention and preparedness: the Gujarat Act 2003, then the DM Act 2005 and NDMA.

• This matches the global shift from Hyogo (2005) to Sendai (2015-2030).

• Big projects in hazard zones: Himalayan dams (Tehri), hydro projects and fast urban growth raise the risk of RIS and of large losses. They need fault mapping, site-response studies and careful siting [2].