March 29, 2011 - 3:50 pm
From NHK:
The latest research on the March 11 tsunami that slammed into Ofunato city in Iwate Prefecture, northern Japan shows that it was nearly 30 meters high.
A joint research team from Yokohama National University and University of Tokyo surveying the Ofunato city shoreline made the discovery.
They found fishing equipment scattered on the high cliff of the city’s Ryori Bay and have determined the tsunami reached as high as 29.6 meters.
The research group says the great height of the tsunami was formed by the shape of the narrow bay. They will continue to survey traces of the tsunami to clarify the scale the tsunami.
Now THAT is “kinetic action”…..
You don’t want to live at the end of a funnel when a tsunami comes along.
Back that googlemap up to 100 miles and check out the undersea ridge that Japan sits on. That sucker is steep. Doesn’t take a lot of imagination to see some tectonic stress going on there.
The scale of the triple whammy is hard to grasp.
Bottom contours act very well as lenses that refract and focus incoming waves according to their wavelength and direction. Shallowing water slows the wavefront. An underwater ‘ridge’ projecting seaward from land will first slow the ‘middle’ of a wide wavefront, and swing the ‘wings’ inward toward the middle, thus taking all the energy of the wide wave and concentrating it in a much narrower path. There’s nowhere for all that water to go but up.
The direction of the approaching swell interacts with the bottom contours to increase or decrease wave height – the bottom ‘lens’ can focus or diffuse incoming wave energy at specific shore locations. Surfers cash in on this phenomenon regularly, not getting out of bed for a swell from direction A but camping on the beach for direction B.
–wonder if anyone has mapped the sea bottoms off, say, the Seattle coastal terrain, and applied the 9.0, 80 miles out, model. Then, someone could plot their elevation –above sea level –and have that knowledge for future reference.
The bottom contours of the Washington coast are well enough known to model such a wave under various assumptions. I’d be surprised if many researchers hadn’t already done so.
You’d still need to know the direction from which the waves would approach, and there are about 600 miles of the subduction zone which could generate – or not – a tsunami in such an earthquake.
Luckily, Seattle and its urban neighbors would face waves of somewhat limited power, due to the restricted entrance to Puget Sound. But all the lowlands and river valleys on the coast would still be at hazard.
Lucifer’s Hammer & Imperial Valley, California.
Niven & Pournelle had it.