Tsunami alert system

The Intergovernmental Oceanographic Commission (IOC) developed a world wide network of sea-level stations - allowing to monitor the level of the ocean in real time - and several tsunami warning centres. Originally, a tsunami warning system was first developed in the Pacific Ocean, after the heavy earthquake of 22 May 1960 in front of the Chilian coast (9.5 on the Richter magnitude scale). Then a large tsunami distroyed Hilo in Hawaii and the coast of Sanriku in Japan. The Pacific Tsunami Warning Centre (PTWC) was established by UNESCO’s Intergovernmental Oceanographioc Commission in 1965. The centre is hosted by the National Oceanic and Atmospheric Administration (NOAA) in Honolulu (Hawaii, USA).

The PTWC receives seismographic and sea-level information from a network of stations throughout of the Pacific in real time as well as data from regional and national alert centres. As soon as an earthquake is recorded, the centre evaluates any possible tsunami risk and sends out alert messages to the countries concerned. In the aftermath of the Indian Ocean tsunami on 26 December 2004, building on this experience, IOC-UNESCO established similar systems for the Indian Ocean, the Caribbean and the seas around Europe to ensure a global cover for tsunami hazards.

At that moment the setup of a Sea Level Station Monitoring Facility was launched. This real-time data system is developed by the Flanders Marine Institute (VLIZ) for IODE (IOC/UNESCO) and several IOC programma's, like the Global Sea Level Observing System Core Network (GLOSS) and the networks under the regional tsunami warning systems in the Indian Ocean (IOTWS), North East Atlantic & Mediterranean (NEAMTWS), Pacific (PTWS) and the Caribbean (CARIBE-EWS). It is operating from Ostend (Belgium). Via this website one can observe the status and rough (not quality-checked) real-time sea level measurements of 430 measuring stations. These are set up along the coasts of the Indian and Pacific Ocean, the Northeast Atlantic Ocean, the Mediterranean and the Caribbean Sea. This system is a quick tool to check the operation of all these measuring stations throughout the world and also allows a first inspection of the rough data stream.

After the tsunami of 26 December 2004 in the Indian Ocean, the Government of Flanders (Belgium) decided to allocate 500.000 EUR a year for the Project Office for IODE (IOC/UNESCO) in Ostende. Every year a dozen of specialised courses are organised here for oceanographic data- and information managers from all over the world to enhance their skill in ocean disasters.

The earthquake in Japan, the subsequent tsunami and alarm

The Pacific tsunami warning system has worked very well. The PTWC issued an alert three minutes after a massive earthquake, measuring 8.9 on the Richter Scale, struck the northeast coast of Japan today (5.46 am GMT). Three minutes later, a tsunami alert for Japan was issued via the Japanese Meteorological Agency (JMA). The PTWC has been updating its alerts regularly since then. Less than 30 minutes later a first tsunami wave hit the Japanese coast.

An overview:

• At 5.55 am (GMT) The alert was extended to the Marshall islands, Micronesia, Indonesia (Jayapula), Papua New Guinea and the Mariana Islands, then to the Russian Federation, Marcus Islands, Guam, Wake Island and Taiwan, China.
• At 6.57 am (GMT) the Japanese Meteorological Agency indicated that a wave of between three and four metres had hit the coast of Sendai (N.E. Japan).
• The first tsunami waves hit the coast of Japan about 20-30 minutes after the earthquake, with a height of at least 3.3m measured at Ofunato at 06:15UTC and 2.8m at Hanasaki at 06:57UTC. Higher waves of up to 10m have been reported at Sendai by Japanese news agencies.
• At 7.05 am (GMT) Waves of between one and two metres were expected to strike the Marshall islands, Micronesia, Indonesia (Jayapula), Papua New Guinea and the Mariana Islands.
• 7.30 am (GMT) - The alert was extended Pacific-wide: Japan, the Russian Federation, Marcu Islands, Mariana Islands, Guam, Wake Island, Taiwan (China), Yap, Philippines, Marshall Islands, Belau, Midway Island, Pohnpei, Chuuk, Kosrae, Indonesia, Paupa New Guinea, Nauru, Johnston Island, Solomon Islands, Kiribati, Howland-Baker, Hawaii, Tuvalu, Cook Islands, Niue, Australia, Fiji, New Caledonia, Tonga, Mexico, Kermadec Island, Polynesia, New Zealand, Pitcairn Island, Guatemala, El Salvador, Costa Rica, Nicaragua, Antarctic, Panama, Honduras, Chile, Ecuador, Colombia and Peru.
• 10.05 am (GMT) – the alert is extended to the American States of California and Oregon.

The website in charge

The progress of the tsunami was attended by many via the Sea Level Station Monitoring Facility. On an ordinary day this website is dealing with 40.000 hits. On Friday 11 March the number of hits increased 10 times. The day after the tsunami, Saturday, the site was visited 66 (!) times more frequently than usually (almost 3 million hits).

After clicking on one of the sea-level stations on the map or in the list, one can survey the sea-level in a graph (period of observation can be chosen). The application is available as well on Google Earth (only last 24 hours are visible then). The status of the measuring stations is checked every 5 minutes.

Sea level in Hanasaki (NE Japan) (8 - 14 March 2011) [More info]	Sea level in Hilo (Hawai) (8 - 14 March 2011) [More info]
Sea level in Acapulco (Mexico) (8 - 14 March 2011) [More info]	Sea level in Talcahuano (Chili) (8 - 14 March 2011) [More info]

Extra visual materials

Animation of the progress of the tsunami of 11 March 2011 in the Pacific Ocean [Credits: VLIZ - www.vliz.be]	Animation showing how a seaquake leads to a tsunami	Animation of the run up of a tsunami
Animation of the progress of a tsunami wave [Credits: IOC-IODE (UNESCO) - www.iode.org]	Education: learning module on tsunami [Available via the e-learning project Planet Ocean]	Education: Simulation of the effect of a tsunami on a tropical coast with (health and damaged) mangroves [Available via the e-learning project Planet Ocean (only available in Dutch version)]