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The 11 March 2011 Earthquake off the Pacific Coast of Tohoku, Japan

With the devastating M9.0 earthquake off the Pacific coast of Tohoku once again the world was reminded of the deadly force of the ocean. So far the figures for confirmed casualties and missing people are 15,429 deaths and 7,781 missing. The scenes transmitted around the world have shocked us all, and the IOC sends it condolences to the people of Japan and pledges to continue its efforts to coordinate the implementation and improvement of tsunami warning systems globally.

traveltimes_japanThe earthquake struck at 0546Z on 11 March with its epicenter some 130km east of the coast of Miyagi prefecture. The magnitude of the earthquake is estimated by the Japan Meteorological Agency (JMA) as M9.0, making it the 4th largest recorded earthquake since 1900. There were hundreds of aftershocks since the main earthquake, many greater than magnitude 6. The first tsunami wave arrived at the coastline nearest to the epicenter within about 15 minutes of the earthquake and in the hours that followed more waves arrived, in one place 30m but often above 10m. Whole communities were washed away and much infrastructure was destroyed.

 

The tsunami propagated east into the Pacific Ocean and the first regional tsunami bulletins were issued by the North West Pacific Tsunami Advisory Centre (NWPTAC) operated by JMA and the Pacific Tsunami Warning Centre (PTWC) at 0555Z. Deep-ocean Assessment and Reporting of Tsunami (DART) buoys close to Japan were triggered and a wave of 1.08m amplitude (mean level to peak) was recorded at DART21418 at 0619Z, confirming that a large tsunami had been generated and was propagating eastward.


 

PTWC initially issued wide spread tsunami warning bulletins for most Pacific Ocean countries and later reduced the number of countries on the basis of updated model results. In total, PTWC issued 27 bulletins during the event and NWPTAC issued 9 bulletins. The WC/ATWC issued its first bulletin at 0600Z and issued a total of 34 bulletins during the event. For a complete inventory of factual information about the event and the warning bulletins issued please see: http://itic.ioc-unesco.org . Across the Pacific Ocean, countries were prepared well in advance for the arrival of the tsunami waves. Hawaii ordered statewide evacuations as waves of over 2m (trough to peak) passed the islands. The west coast of the USAexperienced waves of over 4m (trough to peak) at Crescent City. Waves of over 4m (trough to peak) were also measured down the coast of Chile.

tsunami-height-japanDuring this event, the PTWS operated well and according to expectations. The seismic detection systems were able to identify the location and magnitude of the earthquake within minutes allowing for timely regional warnings to be issued to the Pacific Oceancountries. The DART buoys and sea level monitoring stations worked well and the communications systems allowed for near real-time monitoring of the event. The Regional Tsunami Warning Centres issued timely bulletins and kept the National Tsunami Warning Centres of the PTWS well informed and updated on the progress of the tsunami. However, it seems inappropriate to talk of any "success" in an event that has caused so much loss of life and extensive damage to infrastructure and livelihoods. Since 2004, there have been a number of deadly tsunamis: south Java in 2006; Solomons and Chile in 2007, Samoa/American Samoa/Tonga in 2009; Haiti, Chile and Mentawai (Indonesia) in 2010; and now the Tohoku tsunami in Japan. What each of these has in common is that they were local, rapid onset events, where tsunami waves arrived on the shore quickly, and in some places before warnings were issued or before people could evacuate to safety.

Communities must learn to recognize the natural warning signs and act immediately to save their lives. Focused research is also required to continue updating our knowledge about subduction zones capable of generating great earthquakes and tsunamis. The IOC stands ready to support these activities in collaboration with partners and is more than ever committed to the goal of developing effective end-to-end tsunami warning systems at the regional, national and local level.
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