Effects of Earthquakes
Geography › Mountains, Volcanoes, Earthquakes and Tsunami · Topic 4.10
Earthquakes cause ground shaking, surface faulting, ground failure such as liquefaction and landslides, tsunamis, floods and fires, and bring loss of life, destruction of buildings and infrastructure and long-term economic and social damage. The damage depends on magnitude, depth, ground and the quality of construction, so preparedness and earthquake-resistant building greatly reduce losses.
5 min read · UPSC Prelims · Geography · Mountains, Volcanoes, Earthquakes and Tsunami
At a Glance
- Primary effects Ground shaking, surface rupture, ground deformation
- Secondary effects Landslides, liquefaction, tsunamis, fires, floods
- Social effects Deaths, injuries, homelessness, disease
- Key factors Magnitude, depth, soil, buildings, population
- Mitigation Codes, zoning, early warning, drills
- Exam link UPSC Prelims, Geography: Mountains, Volcanoes, Earthquakes and Tsunami
Where Does It Fit?
This is the tenth topic of the category on mountains, volcanoes, earthquakes and tsunami. The previous topic explained causes and scales, and this one covers the consequences and how to reduce them. The next topic covers tsunamis. Previous topic: Earthquakes – Causes, Focus and Richter Scale. Next topic: Tsunami – Mechanism and Properties.
What Are the Direct Effects of an Earthquake?
In short: earthquakes shake, break and shift the ground, and most deaths come from collapsing buildings.
The effects of earthquakes fall into direct effects, caused by the movement of the ground itself, and secondary effects, set off by the shaking.
- Ground shaking: the main cause of damage; vibrations from body and surface waves shake buildings, bridges and pipelines, and may bring down poorly built structures.
- Surface rupture and ground deformation: the fault may break the surface, forming scarps and cracks, and the ground may be lifted, dropped or shifted horizontally by metres, as in the 2023 Turkey earthquakes in which the ground moved several metres along the fault.
- Change of land and rivers: permanent uplift or subsidence of coasts, and changed river courses; the 1950 Assam earthquake altered the courses of rivers in the Brahmaputra basin.
What Are the Secondary Effects?
| Effect | Description |
|---|---|
| Liquefaction | Water-saturated loose sand and silt behaves like a liquid when shaken; buildings tilt and sink; occurred at Niigata in 1964 and Bhuj in 2001 |
| Landslides and avalanches | Shaking triggers slides on steep slopes, blocking rivers and forming landslide lakes; frequent in the Himalaya |
| Tsunamis | Undersea earthquakes displace water and create waves that travel across oceans, as in Tsunami – Mechanism and Properties |
| Fires | Broken gas pipes and electric lines start fires, as in San Francisco 1906 and Tokyo 1923 |
| Floods | Damaged dams, landslide dams and river changes cause flooding |
| Disease and disruption | Water supply and sanitation fail; hospitals and roads are damaged |
The sudden shift of the ground also affects the Earth as a whole: very large earthquakes, such as the 2004 and 2011 events, are estimated to have slightly shortened the length of the day by a few microseconds.
What Determines the Damage?
The loss in an earthquake depends on several factors. Magnitude and depth set the energy, and shallow earthquakes cause more damage. Distance from the epicentre reduces the shaking. Local soils matter: soft sediments and fill amplify shaking and may liquefy, while hard rock shakes less. The quality of construction is the most important human factor, since unreinforced masonry and badly built concrete frames collapse, while buildings designed to resist earthquakes survive. Population density, time of day and preparedness also decide casualties. As an analytical point, earthquakes of the same magnitude have caused very different losses in different countries, which shows that earthquakes are natural hazards but disasters are made by vulnerability.
What Are the Major Earthquake Events and Lessons for India?
| Event | Magnitude | Notes |
|---|---|---|
| Latur, Maharashtra, 1993 | 6.2 | Shallow earthquake in a region thought to be stable; thousands killed |
| Bhuj, Gujarat, 2001 | 7.7 | About 20,000 deaths; liquefaction and collapse of multi-storey buildings |
| Kashmir, 2005 | 7.6 | Large losses on both sides of the Line of Control |
| Nepal (Gorkha), 2015 | 7.8 | Thousands killed; felt strongly in northern India |
| Myanmar, March 2025 | 7.7 | Sagaing Fault; heavy damage in Myanmar and effects as far as Bangkok |
About 59 per cent of India’s land area, according to the zoning of the Bureau of Indian Standards, is prone to moderate to severe earthquakes, as shown by the seismic zones in Distribution of Volcanoes and Earthquakes – Ring of Fire. The lesson of recent earthquakes is that many casualties come from unsafe old buildings and poor enforcement of codes.
How Can Earthquake Risk Be Reduced?
- Earthquake-resistant construction: follow the Bureau of Indian Standards code, IS 1893, and related codes for design, and retrofit old and critical buildings.
- Land-use planning: avoid building on active faults, loose fill and steep unstable slopes; limit building heights in high zones.
- Early warning and monitoring: seismic networks and, where available, early warning systems.
- Preparedness: drills in schools and offices, emergency kits, community training, and mock exercises by the National Disaster Management Authority and the National Disaster Response Force.
- Response and recovery: search and rescue, medical aid, temporary shelter and rebuilding with safer standards.
Traditional building methods, such as the timber-laced masonry of Kashmir (dhajji dewari) and the wood-framed houses of the Northeast (ikra), perform well in earthquakes, and are being studied for lessons in cheap safe building.
Why Is This Topic Important?
- Disaster management Core GS 3 topic
- India Major earthquakes and zones
- Mitigation Building codes and drills
What Came Next?
The next topic describes the mechanism and properties of tsunamis. Next topic: Tsunami – Mechanism and Properties.
Key People and Terms
- Liquefaction Soil behaving like a liquid
- Surface rupture Fault breaking the surface
- Retrofitting Strengthening existing buildings
- Seismic zone Area of similar hazard
- Vulnerability Likelihood of damage
- Early warning Seconds of notice before shaking
Exam Corner
Points to Remember
- Liquefaction affects loose saturated sand.
- Most deaths come from building collapse.
- Bhuj 2001 had magnitude 7.7.
- IS 1893 is the earthquake design code.
- Earthquakes are hazards; vulnerability makes disasters.
Do Not Confuse With
- Primary and secondary effects Shaking and rupture versus landslides, fires and tsunamis
- Hazard and disaster Natural event versus the loss it causes
- Magnitude and damage Source energy versus local effects
Memory Hook
Shake, crack, slide, flood and burn; good codes and drills turn hazard into survival.
Mains Angle
Questions ask for effects and mitigation. These points add depth.
- Effects Primary and secondary
- Vulnerability Buildings and soils
- Mitigation Codes, zoning, drills
A Question You May Face
An original practice question, not a past paper question.
“Discuss the impact of earthquakes and suggest measures to reduce earthquake risk in India.”
How to Answer
- Effects Direct and secondary.
- Factors Soil, buildings, density.
- India Zones and past events.
- Measures Codes, planning, drills.
GS Relevance
Frequently Asked Questions
What are the main effects of an earthquake?
The main effects are ground shaking, surface rupture, and ground deformation, and secondary effects such as landslides, liquefaction, tsunamis, fires and floods. These cause deaths, collapse of buildings and infrastructure, disease and long-term economic loss.
What is liquefaction?
Liquefaction is the process in which water-saturated loose sand or silt loses its strength and behaves like a liquid when shaken by an earthquake. Buildings on it can tilt or sink, and it caused major damage in Niigata in 1964 and in Bhuj in 2001.
Why do some earthquakes cause more damage than others?
Damage depends on magnitude, depth, distance, local soil, quality of construction and population density. A shallow earthquake near a city with weak buildings and soft soils can cause far greater losses than a larger earthquake at depth or in an empty region.
How much of India is prone to earthquakes?
About 59 per cent of India's land area is prone to moderate to severe earthquakes under the zoning of the Bureau of Indian Standards. The Himalayan arc, the Northeast, Kachchh and the Andaman and Nicobar Islands are in the most severe zones.
How can earthquake risk be reduced?
Risk can be reduced by earthquake-resistant construction following IS 1893, retrofitting old buildings, careful land-use planning, monitoring and early warning, public drills and training, and prepared emergency response by agencies such as the NDMA and the NDRF.
PYQ Practice — Statement Analysis
1 Liquefaction occurs in loose water-saturated sandy soil during an earthquake.
The soil loses strength.
2 Earthquake damage depends only on magnitude.
Depth, soil, building quality and density matter too.
3 The Bhuj earthquake of 2001 occurred in Gujarat.
It had magnitude 7.7.
4 A tsunami is a secondary effect of undersea earthquakes.
The sea floor displaces water.
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