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When the Japan Meteorological Agency issues a tsunami warning, do not disregard it thinking you've got a better handle on the factors in play. The Japanese have

When the Japan Meteorological Agency issues a tsunami warning, do not disregard it thinking you've got a better handle on the factors in play. The Japanese have their country monitored thoroughly and take disaster preparedness more seriously than anything I've seen in the US. http://www.jma.go.jp/jma/indexe.html http://www.jma.go.jp/jma/indexe.html (currently has warning) With historical tsunami information: http://www.jma.go.jp/en/tsunami/list.html http://www.jma.go.jp/en/tsunami/list.html

cossatot 10y ago
The JMA is top notch, no argument here. I didn't 'disregard' their warning, I just made a claim that the tsunami was unlikely to be major. This probably wasn't evident when the JMA's warning was made because it takes a while for the seismic waves to reach a broad-enough distribution of stations to confidently determine the type of earthquake. In reply to many of the comments about tsunami height: A 1-2 m tsunami is a moderate tsunami, not a major tsunami. It can be very damaging to coastal infrastructure depending on the tide, the incidence angle of the waves, and other local factors, but it's simply not in the same magnitude as the major tsunamis that accompany M8+ subduction zone earthquakes. Also, the measured amplitude of a tsunami will vary locally depending on the distance from the source and the geometry of the submarine topography: some areas focus the waves and the tsunami will be much higher, while some areas can spread the tsunami waves out. It's very similar to how a sound may be louder or quieter based on how far one is from the source of the sound and what's in between (walls of certain orientations, trees, etc.).
- deleted 10y ago
  [deleted]
- dweekly 10y ago
  You were right. There was a 90cm tsunami. https://vosocc.unocha.org//GetFile.aspx?xml=4248gjer_l1.html&tid=4248&laid=1 https://vosocc.unocha.org//GetFile.aspx?xml=4248gjer_l1.html...
- rabboRubble 10y ago
  Initial predictions had wave height of 3m. That's high enough to wash a person away were they to stay on the seaside. I would suggest that JMA information be a primary reference in the early hours after a Japan natural disaster instead of the USGS. They have a better handle on event measurements and worst case predictions than the USGS will. Thankfully your assessment turned out to be more in line with observation.
  - shiro 10y ago
    Just note here so that people unfamiliar of tsunamis won't get misconception. 50cm of tsunami is enough to wash people away. It's totally different from 50cm-high wave[1]. 1m of tsunami is deadly if you got swallowed. 3m can easily sweep two-story houses. [1] This illustration depicts the difference: https://twitter.com/_KE_N_/status/295134747603107840/photo/1 https://twitter.com/_KE_N_/status/295134747603107840/photo/1 Calculate the inertia of the water. Also mind the actual tsunami carries lots of debris so you can't easily swim in it.
    - rabboRubble 10y ago
      Very good point. ありがたい、本当にいいポイントですね。　未来に日本へ帰りたい！

cossatot 10y ago

The JMA is top notch, no argument here. I didn't 'disregard' their warning, I just made a claim that the tsunami was unlikely to be major. This probably wasn't evident when the JMA's warning was made because it takes a while for the seismic waves to reach a broad-enough distribution of stations to confidently determine the type of earthquake. In reply to many of the comments about tsunami height: A 1-2 m tsunami is a moderate tsunami, not a major tsunami. It can be very damaging to coastal infrastructure depending on the tide, the incidence angle of the waves, and other local factors, but it's simply not in the same magnitude as the major tsunamis that accompany M8+ subduction zone earthquakes. Also, the measured amplitude of a tsunami will vary locally depending on the distance from the source and the geometry of the submarine topography: some areas focus the waves and the tsunami will be much higher, while some areas can spread the tsunami waves out. It's very similar to how a sound may be louder or quieter based on how far one is from the source of the sound and what's in between (walls of certain orientations, trees, etc.).

deleted 10y ago
[deleted]
dweekly 10y ago
You were right. There was a 90cm tsunami. https://vosocc.unocha.org//GetFile.aspx?xml=4248gjer_l1.html&tid=4248&laid=1 https://vosocc.unocha.org//GetFile.aspx?xml=4248gjer_l1.html...
rabboRubble 10y ago
Initial predictions had wave height of 3m. That's high enough to wash a person away were they to stay on the seaside. I would suggest that JMA information be a primary reference in the early hours after a Japan natural disaster instead of the USGS. They have a better handle on event measurements and worst case predictions than the USGS will. Thankfully your assessment turned out to be more in line with observation.
- shiro 10y ago
  Just note here so that people unfamiliar of tsunamis won't get misconception. 50cm of tsunami is enough to wash people away. It's totally different from 50cm-high wave[1]. 1m of tsunami is deadly if you got swallowed. 3m can easily sweep two-story houses. [1] This illustration depicts the difference: https://twitter.com/_KE_N_/status/295134747603107840/photo/1 https://twitter.com/_KE_N_/status/295134747603107840/photo/1 Calculate the inertia of the water. Also mind the actual tsunami carries lots of debris so you can't easily swim in it.
  - rabboRubble 10y ago
    Very good point. ありがたい、本当にいいポイントですね。　未来に日本へ帰りたい！