Mains Marks Booster     5th August 2023        
  • "Tsunami," from Japanese, means "Harbour wave." It's a series of large, long-wavelength waves in large bodies of water caused by major disturbances above or below the surface, or due to significant water displacement. Despite the name "tidal wave," lunar and solar gravitational forces do not cause tsunamis.
  • Tsunamis can occur due to earthquakes, volcanic eruptions, landslides, underwater explosions, and meteorite impacts. Notable subduction zones causing tsunamis include those off Chile, Nicaragua, Mexico, and Indonesia.
  • Tsunami waves are formed by significant seabed displacements, such as in megathrust earthquakes, marine volcanic eruptions, or submarine landslides. Extra-terrestrial objects falling onto Earth can also cause destructive tsunamis.
  • Wave propagation includes gravity acting to return the sea surface to its original shape, creating ripples that race outward. As tsunamis enter shallow waters, they slow down and increase in height (shoaling effect). Tsunamis can appear suddenly and may involve several waves at intervals of several minutes.
  • Tsunami properties include wave crest, trough, height, amplitude, period, wavelength, and frequency. Normal waves involve horizontal (ocean currents and waves) and vertical (tides) motion, with the actual motion of the water beneath the waves being circular.
  • Tsunami warning systems can provide a three-hour notice of a potential tsunami following an earthquake. These systems monitor changes in water pressure, with data being transmitted to warning centers for analysis and issuing of warnings.

The Indian Tsunami Early Warning System (ITEWS) established in 2007 is an integrated network of seismic stations and tide gauges, with an operational warning center to detect tsunamis and provide timely advisories. Indian scientists can issue a tsunami warning within 10-20 minutes after an earthquake.

NDMA Guidelines on Tsunami:

  • NDMA (National Disaster Management Authority) has developed guidelines to manage the risk of tsunamis through awareness generation, capacity building, education, training, and research & development.
  • The guidelines highlight the importance of effective dissemination of tsunami alerts and warnings to the appropriate agencies and vulnerable coastal communities, coordinated by the Indian National Center for Ocean Information Services.
  • The Bureau of Indian Standards is urged to roll out construction standards for tsunami-resistant designs of structures. These standards would guide new constructions and protection strategies for key infrastructure along the seafront.
  • The guidelines advocate for a robust techno-legal regime involving efficient land-use practices, bio shields, shelterbelt plantation, and mangrove regeneration, all with community involvement.
  • They call for a robust emergency response mechanism involving civil defense volunteers, home guards, State Disaster Response Forces, and the National Disaster Response Force.
  • The guidelines emphasize the importance of conducting exercises that include tsunami scenarios to enhance the efficiency and effectiveness of disaster management during an actual event.
  • Finally, they explore the provisions of the Disaster Management Act 2005 to mainstream the concern of tsunami risk management in disaster management plans at various levels.