Background Notes on the Indian Ocean Tsunami

 

Paris, 30 December 2004

The phenomenon we call “tsunami” is a series of traveling ocean waves of extremely long length generated primarily by earthquakes occurring below or near the ocean floor. Underwater volcanic eruptions and landslides can also generate tsunamis. The tsunami waves propagate across the deep ocean with a speed exceeding 800 kilometers per hour. Waves as they approach the coastlines slow-down and raise in height up to 15 meters or more, producing extreme damage at the coast.

UNESCO is involved in tsunami warning and mitigation through its Intergovernmental Oceanographic Commission (IOC). The IOC, established in 1960, is a body with functional autonomy within UNESCO, established to promote international cooperation and to coordinate programmes in research, services and capacity-building, in order to learn more about the nature and resources of the ocean and coastal areas and to apply that knowledge for the improvement of management, sustainable development, the protection of the marine environment, and the decision-making process of its Member States.

IOC established the International Coordination Group for the Tsunami Warning System in the Pacific (ICG/ITSU) in 1968.  The main purpose of the group is to assure that tsunami watches, warning and advisory bulletins are disseminated throughout the Pacific to member states in accordance with procedures outlined in the Communication Plan for the Tsunami Warning System. The Group has a membership of 26 countries: Australia, Canada, Chile, China, Colombia, Cook Islands, Costa Rica, Democratic People’s Republic of Korea, Ecuador, El Salvador, Fiji, France, Guatemala, Indonesia, Japan, Mexico, New Zealand, Nicaragua, Peru, Republic of the Philippines, Republic of Korea, Russian Federation, Samoa, Singapore, Thailand, and the United States of America. The network includes national tsunami warning centres, regional tsunami warning centres (PTWC, Hawaii; WC/ATWC, Alaska; NWPTIC, Japan; CPPT, Tahiti; and SNAM, Chile) and the International Tsunami Information Centre (ITIC) in Honolulu, Hawaii.

ITIC supports ICG/ITSU by monitoring the activities of the Tsunami Warning System in the Pacific (TWSP), coordinating tsunami technology transfer among Member States interested in establishing regional and national tsunami warning systems, and acting as a clearinghouse for tsunami preparedness and mitigation activities. Every year the ITIC organizes a 2-week training course for professionals from pacific countries dealing with tsunami warning and mitigation.
The Richard H. Hagemeyer Pacific Tsunami Warning Center (PTWC) serves as the operational headquarters for the TWSP.  Both the PTWC and ITIC have been hosted by the USA National Oceanographic and Atmospheric Administration, National Weather Service Pacific Region since their inception in 1965.  The ITIC is further supported by Chile’s Servicio Hidrografico y Oceanografico de la Armada. The TWS is a coordinated international effort currently shared by the UNESCO/IOC ITSU and USA NOAA.

The ITSU system makes use of the hundreds of seismic stations throughout the world that are available in real, or near-real, time to locate earthquakes capable of generating Tsunamis and analyze the faulting properties of the earthquake in order to ascertain the dominant direction of energy release and propagation. It has near real time access via satellite and telephone to over 100 water level stations throughout the Pacific that can be used to verify the generation and possible severity of a tsunami. The system disseminates tsunami information and warning messages to well over 100 points scattered across the Pacific.

The Indian Ocean Tsunami

On Sunday 26 December 2004 at 8:14 p.m. EST, within minutes following an alarm signaling a strong earthquake in the Indian Ocean, NOAA’s Tsunami Warning Centers in Hawaii and Alaska issued information bulletins to all ICG/ITSU member states and other Pacific nations indicating that a magnitude 8.0 earthquake (later upgraded to M9.0 by the U. S. Geological Survey) had occurred off the west coast of Northern Sumatra, Indonesia.  According to the agreed-upon procedures for the International Tsunami Warning System in the Pacific, this event did not pose a threat to the Pacific.  The PTWC (Pacific Tsunami Warning Center), however, continued to monitor the event.

Within a few hours, Vasily Titov, associate director of the Tsunami Inundation Mapping Efforts (TIME) at NOAA’s Pacific Marine Environmental Laboratory in Seattle, Wash. and his counterpart in Japan, Kenji Satake, National Institute of Advanced Industrial Science and Technology,  produced preliminary estimates of the main features of the event. Tsunami travel time maps were quickly prepared using software developed by Dr. Viacheslav Gusiakov, Institute of Computational Mathematics and Mathematical Geophysics, Novosibirsk, RUSSIA). (see all model outputs and maps on http://ioc.unesco.org/itsu/contents.php?id=135). Information was posted on the ITSU web site (http://ioc.unesco.org/itsu ) as from Monday 27 December 2004.

85 percent of all tsunamis occur in the Pacific Ocean, generated in the regions where the main tectonic plates forming the floor of the Pacific collide against themselves or against the continental plates that surround the ocean basin, in an area known as the Ring of Fire.  The Mediterranean and Caribbean Seas also have histories of some locally destructive tsunamis. Tsunamis in the Indian Ocean have been rare and far part in time. This might explain why no tsunami warning system has been  developed in the Indian Ocean.

The Indian Ocean tsunami is now reported to be one of the strongest in the world for the past 40 years.  More than 100,000 lives have been lost and material damage is tremendous.

IOC based on its mandate and experience with ICG/ITSU, will lead an effort to expand the currently existing system in the Pacific to the World Ocean to ensure that appropriate warning systems are available in all regions of the world that are prone to Tsunamis. This decision is fully consistent with the current initiative to build a Global Earth Observation System of Systems.  For that purpose immediate consultations will be undertaken with the Officers of ICG/ITSU and representatives of concerned countries. Furthermore, representatives from all Member States of the Commission will be invited to participate in a Special Session  during the coming XXIIIrd Assembly of the IOC in July of 2005 to set up and adopt the Policy and Technical bases of such a system at the shortest possible delay.

Dr Patricio Bernal
Executive Secretary IOC

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