Friday, March 11, 2011

Saddening news from Japan . . .

Headlines have been dominated by the 8.9 magnitude earthquake and Tsunami -- up to 33 ft high, telephone pole height -- off the NE coast of Japan; with tidal waves racing across the Pacific to impact elsewhere. In California, at least one harbour was hard hit by 8 ft waves.


Sky News has some terrifying footage:

Daily Mail has a useful tsunami wave height/ energy projection plot:

{NB: Tsunamis are of sufficient wavelength that the ocean deeps are shallow to them. They thus follow a sqrt [g*d] wave speed law (g, accel. of gravity, d, depth), and that means that there is a depth lensing effect that can focus the waves. Thus, the old Sailor's saying that "points draw waves." They will also reflect off banks and chains of islands, depending on situations. Bottom-line is they propagate at jet plane speeds -- easily 300 - 600 mph --  across the oceans; then can be focussed on a harbour or point, if there is a bottom contour lens. In the case of the Japanese islands, they seem to be serving as a beam reflector, sending the waves across the Pacific diagonally.  Then, they rise up out of the deeps and surge ashore like the monster waves in the Sky News clip, that are sweeping onshore and overland at maybe ~ 30 mph. In the case of Crescent City, CA, there seems to be a lensing effect, as a similar surge has happened there before.}

Let us heed this warning, here in the Caribbean, for we too are vulnerable.

And let us pray for a Japan facing 1,000 dead, 80,000 missing and entire towns swept by tidal waves. END


F/N: To put radiation exposure in context, cf here on the familiar  banana as a unit of radiation exposure.

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