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Andrew Alden

AGU Day One: Press Conferences

By December 6, 2011

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I took the opportunity to sit in on some press conferences Monday afternoon. The first presented some recent results from the tsunami zone in Japan. Researchers have gotten back into the inundation zone and compared the fresh sand deposits from 2011 to those that were formed in the last great tsunami here, in the year 869. They were quite similar in size, appearance and distribution, which suggests that the two events may represent the typical recurrence interval for the region. (Unfortunately, the 869 tsunami was poorly known at the time the authorities drew up their earthquake/tsunami guidance for the region—one reason it caught people by surprise.)

We were also shown satellite data that luckily crossed the tsunami while it was in the middle of the Pacific. It documented, for the first time, a model of tsunamis in which the waves undergo interference with themselves as they cross seafloor mountains, doubling their size in some places to create "tsunami jets" and cancelling out in others. It's really important to know about tsunami jets when you want to warn possible target regions. Update: NASA's press folks have put up more detail on this part of the briefing.

A presentation showed some of the damage to Japan's enormous harbor barriers. These great and expensive earthworks did not protect their cities well, reducing wave heights by about one-fourth at most. Also, the famous tsunami forest planted at Rikuzentakata was wiped out to the last tree (literally, there is one tree left). So these things don't work very well, although I spoke with a poster presenter later that afternoon who said that the breakwaters may not have stopped the waves, but they did slow them down by several minutes, which can save lives. But what really works is public education and preparedness. In Sumatra in 2004, the coastal areas experienced 90 percent fatalities, but in Japan in 2011 the figure was 10 percent.

The second press conference was about sprites, a subject I've followed closely for many years. The news, to me, was that the Japanese TV network NHK funded a serious research campaign this year in Taiwan and America to find and photograph these remarkable upper-atmospheric lightning creatures, in stereo using two airplanes at once. It should make great TV next year, and meanwhile the scientists have had full use of the data, a real win-win.

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