Tsunamis (Japanese for “harbour wave”), also known as a seismic sea wave, are a series of very large waves with extremely long wavelengths, in the deep ocean, the length from crest to crest may be 100 km and more. When the seafloor abruptly deforms the sudden vertical displacements over large areas disturb the ocean’s surface, displace water, and generate tsunami waves.

1. Of the nearly 7,500 km long coastline, close to 5,700 km is prone to cyclones and tsunamis.
2. States Prone to Tsunami:
   1. Kerala- Alleppey and Earnakulam
   2. Tamil Nadu- Cuddalore, Kancheepuram, Chennai, Kanyakumari, Tirunelveli, Thoothukudi, Villupuram, Thiruvarur, Ramanathapuram, Thanjavur
   3. Andhra Pradesh- Nellore, Prakasam, Guntur. Visakhapatnam, East and West Godavari
   4. Pondicherry
   5. Orissa
3. Between 1998-2017, tsunamis caused more than 2,50,000 deaths globally, including more than 2,27,000 deaths due to the Indian Ocean tsunami in 2004.
4. More than 700 million people live in low-lying coastal areas and Small Island Developing States exposed to extreme sea-level events including tsunamis.

Nodal Ministry: Min. of Earth Sciences (MOES).

Types of Tsunamis:

1. Tectonic Tsunamis: Caused by underwater earthquakes, volcanic eruptions, or fault movements along tectonic plate boundaries.
2. Landslide Tsunamis: Triggered by underwater landslides, which can displace a large volume of water.
3. Meteorological Tsunamis (Metetsunamis): Generated by atmospheric disturbances such as severe storms, rapid pressure changes, or weather fronts.

Criteria to Declare:

The Indian government, like many other governments around the world, relies on various criteria and systems to detect and declare tsunamis. Key components of the criteria include:

1. Seismic Activity: A significant earthquake with a magnitude above a certain threshold (usually around 6.5 or higher) can trigger tsunami alerts.
2. Ocean Buoy Data: Buoy systems are equipped with sensors that can detect changes in sea level. A sudden, abnormal rise in sea level can be indicative of a tsunami wave.
3. Tide Gauge Readings: Provide real-time data on sea level changes. Unusual, rapid and significant increase in fluctuations in sea level, can be a sign of an approaching tsunami.
4. Earthquake Location and Depth: Shallow, undersea earthquakes are more likely to cause tsunamis.
5. Historical Data: Areas with a history of tsunamis are often given higher priority for monitoring and early warning systems.
6. International Coordination: India is part of the Indian Ocean Tsunami Warning and Mitigation System (IOTWMS), which collaborates with other countries in the region.

Mitigation:

The Ministry of Earth Sciences primarily managed these guidelines through agencies like the Indian National Centre for Ocean Information Services (INCOIS) and the National Disaster Management Authority (NDMA).

1. Early Warning System: Network of seismometers, tide gauges, and buoy systems helps for the detection of undersea earthquakes and the issuance of timely warnings.
2. Public Awareness: Educate coastal communities and residents by signage, community drills, and educational materials.
3. Evacuation Plans: Identify safe evacuation routes and locations for residents in case of a tsunami warning.
4. Coordination: Ensure coordination amoung NDMA, INCOIS, Indian Meteorological Department (IMD), and local administrations, to ensure a coordinated response in the event of a tsunami.
5. Building Codes: Enforce building codes and construction standards for more reselience.
6. Community Preparedness: Encourage community-based disaster management and preparedness initiatives. Local communities should be actively involved in planning and response efforts.
7. Research and Monitoring: Invest in research to better understand the tsunami hazard in Indian waters.
8. International Collaboration: Collaborate with neighboring countries and international organizations to share data and expertise related to tsunami warning and response.

NDMA Guidelines:

1. It would be best if you continued using a Weather Radio or staying tuned to a Coast Guard emergency frequency station or a local radio or television station for updated emergency information.
2. Check yourself for injuries and get first aid, if necessary, before helping injured or trapped persons.
3. Help people who require special assistance—Infants, elderly people,
4. Use the telephone only for emergency calls. Telephone lines are frequently overwhelmed in disaster situations. They need to be clear for emergency calls to get through.
5. Wear long pants, a long-sleeved shirt, and sturdy shoes. The most common injury following a disaster is cut feet.
6. Use battery-powered lanterns or flashlights when examining buildings.
7. Battery-powered lighting is the safest and easiest to use, and it does not present a fire hazard for the user, occupants, or building. DO NOT USE CANDLES.
8. Check for gas leaks.
9. Look for electrical system damage.
10. Watch for loose plaster, drywall, and ceilings that could fall.
11. Take pictures of the damage, both of the building and its contents, for insurance claims. Open the windows and doors to help dry the building.

Way Forward

The Indian National Centre for Ocean Information Services (INCOIS) has now developed a system that will be able to predict risk to coastal areas, the height of waves that can hit them, and even pinpoint vulnerable buildings, all in “real-time,” represents a significant improvement in India’s capacity to assess dangers following a tsunami event.