Tsunami Hits The Shores Of New Zealand!!

[David]

You guys are making fun of me! Now come on, don't joke about this. There seem to be a couple of misconceptions.

1) Don't confuse a tsunami -- even a very small one -- with a wind-generated surf wave. Even a small tsunami packs far more energy than a surf (or surface) wave.

2) Tsunami amplitude is not the same as wave height (crest to trough). Tsunami amplitude refers to the height of surge above mean sea level. So if mean sea level at high tide on a particular beach is 9 feet, a tsunami with an amplitude of 1 foot transforms that 9-foot high tide into a 10-foot high tide. It might not sound like a big deal, but it's an enormous difference in water volume at the shore.

This tsunami occurred right offshore of Fiordland, probably on the subduction fault. It's very dangerous when tsunamis occur so close to shoreline because the warning systems in place require more time to generate than a tsunami would require to reach the shoreline from the generating source. So let's say the warning system (& Australia has a very good one) takes 12 minutes from the time of the quake to the time of the warning being sent to authorities. But the tsunami is traveling at speed v & can therefore reach the closest shorelines to it within, say, three or four minutes. The only "warning" people on those nearby beaches would have is the quake itself.

And big quakes like this one can always generate subaerial & submarine landslides & slumps, which can create their own extremely dangerous tsunamis. It didn't happen this time, but it has happened in New Zealand's past, & will happen in the future.