What are the causes of origin of tsunami? Analyse the landscape and effects of Indian tsunami, 2004.

Introduction: A Tsunami (Japanese: 'Tsu' = harbor, 'Nami' = wave) is a series of catastrophic, high-velocity oceanic water waves generated by sudden, large-scale vertical displacement of the seafloor water column.

1. Causes of Origin of Tsunamis:

• 1. Undersea Megathrust Earthquakes (Primary Cause - $>85$): Sudden vertical displacement along a subduction zone fault on the seafloor exceeding Magnitude $ge 7.5 ext{ }M_w$.
• 2. Submarine Landslides & Coastal Slumps: Massive displacement of continental shelf sediments dropping into deep ocean trenches.
• 3. Submarine Volcanic Eruptions & Caldera Collapses: Explosive volcanic explosions under the sea (e.g., Krakatoa 1883, Hunga Tonga 2022).
• 4. Oceanic Meteorite / Asteroid Impacts (Extremely Rare).

2. Landscape and Manifestation of the 2004 Indian Ocean Tsunami:

• Seismological Trigger: On 26 December 2004 (06:29 AM IST), a colossal Magnitude 9.1–9.3 Megathrust Earthquake struck off the west coast of Northern Sumatra (Indonesia) at a shallow focal depth of 30 km, rupturing a 1,300 km section of the Sunda Megathrust (India plate subducting beneath the Burma microplate).
• Wave Dynamics: Radiated across the Indian Ocean at jetliner speeds ($>700 ext{–}800 ext{ km/h}$). Upon reaching shallow coastal waters (Shoaling effect), wave velocity decreased while wave heights surged into monstrous walls of water 10 to 30 metres high.

3. Multi-Dimensional Devastating Effects in India:

• 1. Catastrophic Loss of Lives: Over 230,000 people killed across 14 countries; in India, over 16,000+ casualties occurred, with worst devastation in Tamil Nadu (Nagapattinam, Cuddalore, Chennai Marina Beach), Andhra Pradesh, Kerala, and Pondicherry.
• 2. Decimation of Andaman and Nicobar Islands: Submergence of coastal villages; Indira Point (India's southernmost tip) submerged permanently into the sea by ~4.25 metres; widespread damage to Car Nicobar.
• 3. Ecological & Agrarian Salinization: Seawater intrusion salinized thousands of hectares of coastal agricultural paddy fields, destroyed coral reefs, and flattened coastal mangrove forests.
• 4. Paradigm Shift in Disaster Governance: Catalyzed the establishment of the state-of-the-art Indian Tsunami Early Warning Centre (ITEWC) at INCOIS, Hyderabad in 2007 and the enactment of the Disaster Management Act, 2005.

Conclusion: The 2004 Tsunami transformed disaster paradigm globally, leading to deep-ocean BASS tsunami buoys and international real-time warning networks.