Trap: Thinking all tsunamis are caused by earthquakes (they can also be caused by underwater volcanic eruptions, landslides, and meteor impacts).
Most confused: Epicentre vs Hypocentre (Focus) — epicentre is point on surface directly above focus.
Key anchor: Plate tectonics — Indian plate moving north at ~5 cm/year → constant stress against Eurasian plate.
Current affairs hook: Turkey-Syria earthquake (Feb 2023) — 50,000+ dead; Nepal earthquakes (2015, 2023); Japan tsunami (2011); India's NDMA guidelines for earthquake preparedness.
Mains hinge: "India's vulnerability to earthquakes and tsunamis is shaped by its geological setting. Discuss the mitigation strategies adopted and their limitations."
Core Concept
Causes of Earthquakes
Plate Tectonics: Earth's lithosphere divided into plates — movement along plate boundaries releases energy
Faulting: Sudden slip along a fault → seismic waves (P-waves, S-waves, Surface waves)
Types of Boundaries: Convergent (collision), Divergent (spreading), Transform (slipping)
Which seismic zone covers entire NE India? (Zone V)
Geography
2023
Mains
"Indian ocean tsunami early warning system — components and effectiveness."
GS1/GS3
2022
Prelims
Koyna earthquake — reservoir-induced seismicity
Geography
2021
Prelims
2004 Tsunami — location of epicentre (Sumatra)
Geography
2020
Mains
"India's seismic vulnerability and disaster preparedness." Discuss
GS3
2019
Prelims
Indian Tsunami Early Warning System (ITEWS) — where? (INCOIS)
Geography
2018
Prelims
Bhuj 2001 — magnitude and zone
Geography
Statement Elimination Guide
"The epicentre of an earthquake is the point where rupture originates underground." → FALSE. That's the focus/hypocentre. Epicentre is the point on the surface directly above the focus.
"Tsunamis can only be caused by earthquakes." → FALSE. Volcanic eruptions, submarine landslides, and asteroid impacts can also cause tsunamis.
"India has a tsunami early warning system." → TRUE. ITEWS at INCOIS, Hyderabad, operational since 2007.
"All coastal areas of India are prone to tsunamis." → FALSE. East coast more prone; west coast less vulnerable (distal tsunamis attenuated by topography).
Current Affairs Hook
Turkey-Syria Quake (2023): M7.8 — lessons for Himalayan earthquake preparedness (populations at risk).
Nepal Earthquake 2023: M6.4 — reminder of Himalayan seismic risk.
Chennai Floods (2015): Not tsunami but coastal surge — but raised coastal disaster awareness.
New Building Codes: Uttarakhand mandatory earthquake-resistant construction; review of IS 1893.
Interlinkages
Plate Tectonics: Indian plate-Eurasian plate collision → Himalayas (convergent boundary) — also causes continued seismic activity
Himalayan Geology: Inverse topography vs orogeny — ongoing mountain building
Disaster Management: NDMA, NDRF, early warning — institutional response
Urban Planning: Delhi, Mumbai, Bengaluru — high-density cities in moderate-high zones — building codes enforcement critical