Indian Tsunami Early Warning Centre

Also called: ITEWC, INCOIS tsunami warning centre · Topic: Natural Hazards and Disaster Management in India · NCERT: Class 7, Ch 2 "India and Her Neighbours"; Class 11, Ch 6 "Natural Hazards and Disasters: Causes, Consequences and Management"

Meaning

The Indian Tsunami Early Warning Centre (ITEWC) is India's national centre that detects tsunamis and sends out warnings. It works at INCOIS (Indian National Centre for Ocean Information Services), Hyderabad, under the Ministry of Earth Sciences. It has been working since October 2007.

It matters because in 2004 the Indian Ocean had no warning system, and coastal people had no time to escape. Today ITEWC can send an advisory within about 10 minutes of an undersea earthquake. It also gives tsunami services to 25 Indian Ocean countries [2][3].

Explanation

Why it was set up

• Trigger: the 26 December 2004 tsunami
• A magnitude 9.1 earthquake struck off the north-west coast of Sumatra, Indonesia.
• It was the third-largest earthquake in the world since 1900 [5].

• More than 2,30,000 people died in 14 countries around the Indian Ocean [5]. India lost over 10,000 people (verify the current official figure).

• The gap it exposed

• The Pacific had a warning system, but the Indian Ocean did not.

• A tsunami crosses whole oceans, so no single country can manage the risk alone.

• The response

• India set up ITEWC in response to the 2004 tsunami [2].
• India also joined the international tsunami warning system.

How it works: from earthquake to warning

• Step 1, detect the quake: seismic stations record an undersea earthquake. Within minutes they find its location, depth and magnitude.
• Step 2, check the open sea: bottom pressure recorders (BPRs) sit on the deep sea floor.
• A tsunami passing overhead changes the weight of the water above them.

• They record this change in pressure.

• Step 3, confirm at the coast: tide gauges measure sea level at the shore. They show whether a wave has actually arrived.

• Result: an advisory goes out within about 10 minutes of the earthquake.

Instrument	Where it sits	What it tells the centre
Seismic stations	On land	Where the quake was, how deep and how strong
Bottom pressure recorders	Deep sea floor	Whether a tsunami is moving across the ocean
Tide gauges	Coast	Whether the wave has reached the shore

Why fast detection is possible but hard

• Tsunami (Japanese for "harbour wave"): a series of long ocean waves, also called a seismic sea wave. It forms when the sea floor moves suddenly and lifts or drops the whole column of water above it.
• In the deep ocean
• The wave moves fastest, at about 700-800 km/h, as fast as a jet plane.

• It is only about 1-2 m high, so ships barely notice it. This is why sea-floor sensors (BPRs) are needed to spot it.

• Near the coast

• The wave slows down. Its back catches up with its front, so the water piles up to 15 m or more. This piling up is called shoaling (the change in a wave as it moves into shallower water).
• So a warning must reach the coast before the wave slows and grows.

Its regional role

• Since 2011, ITEWC has been a UNESCO-IOC Regional Tsunami Service Provider (RTSP) for the Indian Ocean. UNESCO-IOC is UNESCO's Intergovernmental Oceanographic Commission.
• It works under the Indian Ocean Tsunami Warning and Mitigation System (IOTWMS).
• It provides tsunami services to 25 Indian Ocean countries [2][3].

Where it occurs

• Headquarters: INCOIS, Hyderabad, under the Ministry of Earth Sciences. It has worked since October 2007.
• Area served: the Indian Ocean. It has been an RTSP since 2011 and serves 25 countries [2][3].
• India's two tsunami source zones it watches. A subduction zone is a place where one tectonic plate sinks below another. Such zones cause the largest earthquakes and most tsunamis.

Source zone	Sea	Region threatened
Andaman-Sumatra subduction zone	Bay of Bengal / Andaman Sea	Andaman and Nicobar Islands, east coast (Tamil Nadu, Andhra Pradesh, Odisha, West Bengal)
Makran subduction zone (off Pakistan and Iran)	Arabian Sea	Gujarat, Maharashtra and the west coast

• Places hit in 2004 that shaped its design:
• Nagapattinam district, Tamil Nadu: most deaths on the Indian mainland.
• Car Nicobar: badly damaged.
• Indira Point, Great Nicobar: land sank, and part of it went under the sea.

• Aceh Province and Banda Aceh, Sumatra: the worst-hit area in the world [6].

• Last-mile link: the Tsunami Ready villages in Odisha, recognised in 2020:

• Venkatraipur (Ganjam) [4]
• Noliasahi (Jagatsinghpur) [2]

Don't confuse with

• INCOIS vs ITEWC: INCOIS is the parent organisation in Hyderabad, under the Ministry of Earth Sciences. ITEWC is the tsunami warning centre that works inside it.
• IOTWMS: the Indian Ocean Tsunami Warning and Mitigation System is the whole regional system. ITEWC is one Regional Tsunami Service Provider working under it.
• Tsunami Ready: a UNESCO-IOC programme that recognises prepared coastal communities. A community must meet 11 indicators [2]. ITEWC detects tsunamis and issues warnings. Tsunami Ready makes sure villages can act on those warnings.
• Bottom pressure recorder vs tide gauge: a BPR sits on the deep sea floor and detects a passing tsunami through a change in water pressure. A tide gauge stands at the coast and confirms that the wave has arrived.

Prelims Hooks

• ITEWC is at INCOIS, Hyderabad, under the Ministry of Earth Sciences. It has worked since October 2007.
• ITEWC has been a UNESCO-IOC Regional Tsunami Service Provider since 2011 and serves 25 Indian Ocean countries [2][3].
• ITEWC can issue an advisory within about 10 minutes of an earthquake.
• Trap: tsunamis are fastest in the deep ocean (about 700-800 km/h) and slow down near the coast. A statement that they are "faster in shallow water" is wrong.
• India's two tsunami source zones: Andaman-Sumatra (Bay of Bengal) and Makran (Arabian Sea, off Pakistan and Iran).
• The first Tsunami Ready communities in the Indian Ocean region were Venkatraipur (Ganjam) and Noliasahi (Jagatsinghpur), both in Odisha (2020) [2][4].

Mains Points

• A policy chain from detection to the village (GS-III)
• Detection: ITEWC (2007) uses seismic stations, BPRs and tide gauges, and issues advisories in about 10 minutes.
• Regional role: ITEWC became an RTSP in 2011 and serves 25 Indian Ocean countries [3].
• Community level: Tsunami Ready villages in Odisha (2020) [2][4].

• This chain matches the focus on early warning in the Hyogo (2005) and Sendai (2015-2030) frameworks.

• Why India needs the system

• Two subduction source zones lie close to India: Andaman-Sumatra and Makran.
• Coasts such as Nagapattinam and the Andaman and Nicobar Islands are low-lying and crowded.

• In 2004 there was no warning, so there was no time to evacuate.

• Limits of the system

• A near-field tsunami (one that starts close to the coast) leaves very little time. In 2004 the Andaman and Nicobar Islands were hit within minutes.
• Warnings must be backed by other measures:
  • drills and evacuation maps
  • control on building along the shore (CRZ Notification 2019)
  • natural buffers, such as the Pichavaram and Muthupet mangroves (Tamil Nadu) and the Bhitarkanika mangroves (Odisha)

Related concepts

• Tsunami
• 2004 Indian Ocean tsunami
• Coastal defence by natural buffers

Read more

• Tsunamis and coastal defences