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The word ‘tsunami’ was largely unfamiliar in India until 26 December 2004, when a massive 9.2 magnitude earthquake struck northwest of Sumatra, Indonesia. The resulting tsunami reached the Andaman and Nicobar Islands within 25 to 30 minutes and the mainland’s eastern and western shores within 2 to 5 hours. The disaster claimed 230,000 lives, destroyed vast amounts of property and livestock, and caused over USD 10 billion in damages.
In response, the Intergovernmental Oceanographic Commission (IOC) under UNESCO, along with governments from vulnerable coastal nations, recognised the urgent need for an early warning system to mitigate future tsunamis. Countries like India, Australia, Indonesia, Oman, and Malaysia took the lead in developing regional systems, with the IOC/UNESCO facilitating collaboration and knowledge-sharing with Japan and the USA, which already had systems for the Pacific Ocean.
INDIA’S DIVE INTO EARLY WARNING SYSTEM
India chose to develop its own indigenous early warning system rather than rely on foreign technology. The Ministry of Earth Sciences (MoES) tasked the Indian National Centre for Ocean Information Services (INCOIS) in Hyderabad with leading the effort. INCOIS collaborated with key institutions such as the India Meteorological Department (IMD), National Institute of Ocean Technology (NIOT), National Centre for Coastal Research (NCCR, formerly ICMAM), Survey of India (SoI), and the Indian Space Research Organisation (ISRO). IMD established a network of broadband seismometers for real-time earthquake detection, while NIOT deployed tsunami buoys in the Bay of Bengal and Arabian Sea for real-time data transmission. The SoI networked sea-level gauges (tide gauges) at ports and harbours for real-time data transmission, and NCCR focused on coastal mapping and tsunami wave modelling. ISRO provided satellite-based communication for real-time data transmission. INCOIS integrated all this data and established automated processes for real-time earthquake detection and early warning issuance with minimal manual intervention. The fully operational Indian Tsunami Early Warning Centre (ITEWC) was inaugurated on 15 October 2007 and was later designated by IOC/UNESCO as a Regional Tsunami Early Warning Provider for the Indian Ocean region in 2012.
At the time of the 2004 disaster, existing warning systems in Hawaii, USA, and Tokyo, Japan, were limited to the Pacific Ocean. These systems could detect the location and magnitude of earthquakes worldwide, issuing general warnings based on earthquake magnitude. The basic assumption was that an earthquake occurring on the
seafloor could generate a tsunami wave proportional to its magnitude. Usually, an earthquake of 6.5 magnitude was
considered capable of generating a local tsunami, while a magnitude above 7.5 could generate a basin-wide tsunami.
Although both centres issued gross warnings for the Indian Ocean soon after the 9.2 magnitude earthquake on
26 December 2004, they failed to alert or sensitize the Indian Ocean countries, primarily due to a lack of understanding and preparedness.
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Relying solely on magnitude often led to false alarms, as not all undersea earthquakes produce tsunamis, and
those that do may affect coastlines unevenly. Normally, they strike at certain locations with varying strengths (wave
heights) at different times, depending on factors like the distance from the epicentre, tsunami wave directivity, and nearshore bathymetry.
To reduce false warnings, ITEWC incorporated additional analysis of earthquake types alongside magnitude,
as the type of earthquake indicates whether it will generate a powerful tsunami. For instance, a reverse fault
earthquake, where one block of the earth moves upward relative to another, is more likely to generate a tsunami than
a strike-slip earthquake, which involves horizontal movement. The type of earthquake determines how the water column above the epicentre is disturbed, leading to tsunami wave generation. The earthquake on 11 April 2012, west of Sumatra, Indonesia, exemplified this distinction. Despite a magnitude of 8.6, it did not generate a powerful tsunami,
leading ITEWC to issue evacuation warnings only for three islands in the Andaman and Nicobar region, while
the mainland received alerts requiring no evacuation. This nuanced approach, supported by numerical modelling of
wave propagation, has since become standard practice in tsunami early warning systems worldwide.
Today’s tsunami early warning systems can detect and assess earthquakes accurately, issuing initial bulletins
within 10 minutes and location-specific warnings within 20 minutes. Quick early warnings are essential as
tsunami waves travel in deep waters at jet-engine plane speeds (~ 700-800 km/hr), reaching shores within minutes to
hours depending on the distance from the epicentre. In 2004, for example, the first tsunami waves reached the Andaman and Nicobar Islands in less than 20-30 minutes and mainland locations like Nagapattinam, Chennai, Vizag,
Kollam, Alappuzha, and Vypin within 2.5 to 5 hours, causing widespread destruction.
Current systems focus primarily on seismically triggered tsunamis, which account for over 90% of events. However,
tsunamis caused by other factors, such as meteor impacts, landslides, or volcanic eruptions, remain challenging to predict. Early warnings in such cases are possible only if tsunami waves propagating toward the coast in deep
oceans are detected by satellites or in situ instruments like tsunami buoys. However, such warnings may be less
effective due to delays in detection.
EARLY WARNING AND LOCAL UNDERSTANDING
While India’s warning and communication systems are robust, they are only as effective as the response they generate. The high death tolls from disasters like the Kedarnath floods (2013), Cyclone Ockhi (2017), and recent
landslides in Wayanad highlight the need for better local understanding and action. For example, tsunami impacts
vary greatly depending on local vulnerabilities, such as low-lying areas with dense populations or critical
infrastructure. This underscores the importance of prior mapping of vulnerability and hazard assessment for informed decision-making.
Disaster management in India is primarily the responsibility of state governments, with the State Disaster Management Authority (SDMA) playing a key role. Each state should have a comprehensive disaster management
plan covering all types of disasters, natural and man-made, to ensure effective and timely execution. The management plan should include clear guidelines for coordination between district/taluka level officials, police, fire departments, medical teams, and other agencies. Effective evacuation plans require identifying safe shelters and ensuring they are equipped with essential services.
Regular training is also crucial, as officials responsible for disaster management often rotate between roles.
To address this, ITEWC conducts annual workshops for state and district authorities in all nine coastal states and
union territories, helping them understand warning protocols and coordinate responses effectively. Similar training
workshops to deal with other disasters also need to be designed and executed for emergency responders and government officials to keep them abreast and focused.
TSUNAMI-READY PUBLIC
Public awareness is another critical component of effective disaster management. Educating communities about
disaster risks and prevention measures empowers them to take proactive steps. Awareness campaigns, drills, and educational programmes can instil a culture of preparedness and prevention. Regarding tsunami preparedness,
coastal communities need to know the basic actions to take when receiving a tsunami warning, such as recognising
safe evacuation routes and contacting local authorities for assistance. The IOC/UNESCO’s “tsunami-ready community” certification programme promotes this awareness. In India, two communities in Odisha—Venkatraipur
in Ganjam and Noliasahi in Jagatsinghpur—were certified as “tsunami-ready” in 2020. Expanding this certification to
more vulnerable coastal areas will require active involvement from local administrations, guided by the SDMA and
ITEWC. Similar awareness programs for communities in landslide-prone areas, flood-prone areas, forest fire-prone
areas, etc., should be periodically designed and executed to minimize loss of life and improve disaster management.
Image Courtesy: Indian National Centre for Ocean Information Services (INCOIS)
Communication systems must be regularly tested to avoid failures, and mock drills should be conducted periodically
to ensure readiness. In the case of tsunamis, IOC/UNESCO coordinates biannual communication tests and biennial
Indian Ocean tsunami drills involving early warning centres and local governments, with ITEWC coordinating activities in India. These tsunami mock drills also involve evacuations in selected villages/districts. Periodic tests
are necessary to prevent complacency from creeping into the system over time.
Disaster mitigation involves a range of activities designed to minimize potential damage and loss of life. Effective
mitigation strategies can save lives, reduce economic losses, and accelerate recovery. Engaging communities in
mitigation efforts ensures that local knowledge and needs are integrated into disaster planning. Community based
approaches include constructing safe shelters, developing evacuation plans, and establishing local disaster response teams. Participatory mapping and risk assessments help communities identify vulnerabilities and implement appropriate mitigation measures. A key aspect of disaster mitigation is the construction of resilient infrastructure, such as earthquake-resistant buildings, tsunami flood-proof structures, storm-resistant utilities, etc. Additionally, natural barriers like mangrove forests, which acted as protective shields during the 2004 tsunami, play a crucial role in safeguarding coastal communities.
In conclusion, accurate early warnings are essential but not sufficient for effective disaster management. A coordinated response, grounded in an understanding of local vulnerabilities and the ability to make informed decisions, is crucial to minimizing loss of life and property during tsunamis and other disasters. Ensuring that all levels of government, from national to local, are prepared and responsive is key to building resilient coastal communities in India. Leveraging innovation and technology enhances resilience by providing new tools for disaster prediction, response, and recovery. This includes data analytics, remote sensing, artificial intelligence, and mobile applications. Education and training are vital for building resilience, including disaster preparedness education in schools, professional training for emergency responders, and capacity building for government officials. Building resilience is not just about surviving disasters but thriving in their aftermath. It requires a collective effort across all sectors and levels of society.
*The writer is MoES Chair Professor/Scientist and Former Director, Indian National Centre for Ocean Information
Services (INCOIS), Hyderabad.
