I saw again a rebroadcast (for the second time) of "Nature" "Condition Black", the record waves on north shore of Hawaii on Jan 28 1998. The biggest waves since then were a couple of weeks ago, and right now, today, there is a high surf warning for a 15-17 foot swell (means much bigger breakers locally). The show also talks about a 1969 episode of Giant waves...that did a lot of damage...tore up roads and houses. Anyhow, as a change from death and destruction I loved watching this...I could watch it over and over...along with the "Nature" called "Volcano Watchers", about the late Krafts (killed on Mt. Unzen in, I think, 1992).

These giant swells are deep water waves in the deep ocean. Tsunamis are shallow water waves because of their enourmous wavelengths (100+ km?). These giant waves have periods over 20 s and, in the deep ocean, probably wavelenths of several hundred meters. Their velocity is controlled by their period, not by water depth. I'd guess they travel 80 or 100 km/hr, rather than 700 or 800 km/hr for a tsunami in the deep ocean.
Chris

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