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It was 15 years ago, December 26, 2004. An earthquake of phenomenal power was triggered in the Indian Ocean, causing a gigantic tsunami which was going to kill in its path nearly 226,000 people in Southeast Asia . Since then, the international community has entrusted the Intergovernmental Oceanographic Commission of Unesco with the task of coordinating the implementation of warning systems. Srinivasa Kumar Tummala, head of the Indian Ocean area, takes stock of the progress of the tsunami warning system in the region.
RFI : How does the tsunami warning system in the Indian Ocean work ?
Srinivasa Kumar Tummala : The Indian Ocean Tsunami Warning and Mitigation System (IOTWMS) is based on an international collaboration in which States share their observation and detection networks. Upstream of the system are the three tsunami warning centers under the jurisdiction of Australia, India and Indonesia. When an earthquake occurs, these warning centers provide information on the response and tsunami forecasts to the national warning centers of the Member States of the Indian Ocean warning system. The latter have the sovereign responsibility of alerting their populations to a possible threat of tsunami. Each country has its own procedures to warn coastal populations of a future risk.
Initial tsunami warnings take into account the location of the earthquake epicenter and its seismic characteristics. The confirmation of the tsunami is carried out in a second step thanks to the tide gauge network and to the tsunameters [buoys capable of detecting large bodies of water, editor's note] which measure the sea level. Every two years, we organize at the he scale of the Indian Ocean is a training exercise which enables the countries bordering it to test their alert and evacuation procedures for threatened populations. The next exercise, called IOWave20, will be held in October 2020. In addition, the IOTWMS regularly sets up capacity-building workshops in the areas of tsunami risk assessment, wave modeling or standard procedures. The IOTWMS secretariat is based in Perth, Australia, while the Indian Ocean Tsunami Information Center is located in Jakarta, Indonesia.
Of the 28 countries bordering the Indian Ocean, what has changed since 2004 ?
Much has been accomplished within IOTWMS in the fifteen years since the 2004 Indian Ocean tsunami. In 2004, equipment for measuring earthquakes and tsunamis was extremely limited in the region. Today, there are more than 150 so-called “broadband” seismometers and more than a hundred sea level measurement stations provide real-time information to the countries of the Indian Ocean. In 2004, there was no official channel of communication between the countries of the area to prevent the imminence of a tsunami. From now on, the IOTWMS has established communication axes by GTS [Global Telecommunication System, NDLR], email, SMS and fax allowing the immediate notification of information relating to a possible tsunami to the countries bordering the Indian Ocean.
The Indian Ocean is now undeniably much better armed against tsunamis than it was in 2004. However, due to the nature of the danger, it is very important that countries continue to keep the system in an operational state.
But is the Indian Ocean tsunami warning system really fully operational today ?
The ultimate goal of the system is the evacuation of one or more populations due to a proven risk of tsunami. It depends on the holistic functioning of the end-to-end system. During the first ten years of IOTWMS development , the main focus was on the components upstream of the warning centers. Attention is now focused on the downstream components of local relief organizations and coastal communities. But some aspects deserve to be improved in the Indian Ocean, such as the Makran subduction alert system off the coast of Iran and Pakistan, where a tsunami could strike coastal populations in the space of a few tens of minutes.
Why did the tsunami warning system not work properly in 2018 when the city of Palu, on the island of Celebes in Indonesia, was hit by a tsunami ?
The Palu tsunami, which occurred on September 28, 2018, was caused by underwater landslides induced by an earthquake. While the BMKG [Indonesian government agency for meteorology, climatology and geophysics, editor's note] issued an alert for the Indonesian coast in just five minutes, the expected tsunami devastated the coast of Palu in just three minutes. This very short period of time only allowed people to flee thanks to their prior knowledge of the warning signs of a tsunami. The Sunda Strait tsunami [separating the Indonesian islands of Java and Sumatra, editor's note] on December 22, 2018 was caused by the eruption and partial collapse of the Indonesian volcano Anak Krakatau, opposite which no early warning was possible. These events have highlighted the fact that tsunamis generated by atypical near field sources (coastal subsidence, landslides and collapse of volcanic slopes) are very complex from the point of view of early warning. This underscored the urgent need to update risk assessments, build alert capacities and improve the preparedness of communities to deal with such events.
Countries need to share more real-time data from their observing centers, and to implement new methods of detecting tsunamis that are from atypical sources. Developing and maintaining a culture of self-evacuation is important in saving lives in the face of locally generated tsunamis. Consequently, it is essential to improve people's awareness and their preparation to allow a rapid and appropriate response, both to official alerts and to natural signs of a possible tsunami.
How could the tsunami warning system be improved ?
While tsunami warning systems have demonstrated their effectiveness in mitigating the overall impact of tsunamis, the cases of Palu and Sunda Strait have highlighted the challenges that we continue to face. Within the IOTWMS, there are still some key initiatives to pursue in order to improve the alert system. We can notably cite, to improve the observation network, the use of new technologies such as the GNSS system [a localization and navigation system, combining several systems with global coverage, in particular the American GPS system, the Russian Glonass system and the European Galileo system, editor's note]. We will also have to update the tsunami risk assessments to include all sources having an impact on the Indian Ocean, and strengthen the end-to-end alert chains involving national tsunami warning centers, organizations of disaster management and the media. And, of course, we must continue to improve people's preparedness for the impending tsunamis.
Words translated from English by Nicolas Sanders