UPSC Mains 2017 GS Paper 3 Q18: model answer

On 26 December 2004, a magnitude 9.1 earthquake off Sumatra lifted the seabed by several metres. Within hours, waves struck 14 countries, killing about 2.3 lakh people. In India, more than 10,000 died, mostly in Tamil Nadu's Nagapattinam and the Andaman and Nicobar Islands. There was no warning system in the Indian Ocean.

Factors responsible for tsunamis

• Undersea earthquakes at subduction zones, where one plate is thrust under another and the seabed moves vertically.
• Submarine landslides that displace water.
• Volcanic eruptions in or near the sea, such as Krakatoa (1883) and Hunga Tonga (2022).
• Rarely, meteorite impacts.

Effects on life and the economy

• Deaths and injuries, with women and children hit hardest.
• Fishing communities lost boats, nets and harbours.
• Farmland ruined by salt water for years.
• Tourism, ports and coastal infrastructure damaged.
• Psychological trauma and orphaned children.
• Livelihood loss for salt-pan workers and coastal labourers.
• Ecological damage to corals and beaches; villages behind mangroves, as at Pichavaram, suffered less.
• Nuclear safety: the Kalpakkam plant shut down safely, but the scare led to new reviews.

Preparedness under NDMA's 2010 guidelines

• Early warning: the Indian Tsunami Early Warning Centre at INCOIS, Hyderabad (2007), which warns within minutes.
• Hazard and vulnerability maps of the coast.
• Coastal zone regulation and setback lines.
• Bio-shields: mangroves and shelterbelts.
• Tsunami-resistant design for buildings near the shore.
• Shelters and evacuation routes, signposted.
• Awareness, drills and community training.
• Institutional roles for states, districts and the Coast Guard.
• Protecting critical infrastructure like ports and power plants on the coast.

Since 2004

• INCOIS now serves as a regional tsunami service provider for the Indian Ocean.
• Odisha's Venkatraipur and Noliasahi became UNESCO-certified 'Tsunami Ready' communities in 2020.

The 2004 waves came without warning; the next one will not.