Friday, March 11, 2011


Most of you have probably heard of the terrible Japanese earthquake and resulting tsunami.  Tsunami warnings are still in place along the US West Coast as I write this post.

Tsunamis are initiated by processes that cause the displacement of a water column and can be produced by earthquakes, landslides, volcanic eruptions, etc.  They do not behave like the waves you see on a beach.  Tsunamis have very long wavelengths, typically 100 km or longer.  They move very fast - often several hundred kilometers per hour.  If you are on a boat in the open sea, you probably won't even notice as the ridge and crest of a tsunami passes.

A tsunami travels faster in deep water than in shallow water, and this is what leads to catastrophic inundation in coastal areas.  As a tsunami approaches a coastal area, the wave slows, and water mass in the wave crest builds and deepens, leading to flooding at elevations above the normal sea level.

A remarkable animation of the 2004 Indian Ocean tsunami produced by NOAA is available here.


  1. I remember watching a TV special a few years ago on the 2004 tsunami. Divers near the location of the earthquake epicenter found underwater cliffs up to 30 feet or more in height, if I remember correctly, where the ground on one side of the fault line had risen suddenly. It would be interesting to know what you would feel (if anything) being on a ship directly above it at the time.
    This page has some interesting photos of today's tsunami:
    I especially like photo #7 which shows the tsunami crests breaking far offshore.

  2. i heard the wasatch line was supposed to go off? just wondering if you knew more