By Giancarlo Thomae
Last night a magnitude 8.3 earthquake devastated Chile. The quake generated a tsunami here in Santa Cruz, CA. When tsunami waves (Japanese translation: Harbor waves) are generated, they travel on the sea floor faster than a jet airplane. When the energy hits the continental shelf, the tsunami wave slows and breaks like a normal wave. Although earthquake generated tsunamis are actually very large waves, tsunamis break differently on our coast than you might expect.
The longer the wave length (top to top) the more energy is in the wave. Notice how long period swells break less often than short period swells (more time between swells but are a lot more powerful)? Most waves along our shore these days are about 3 feet tall with a wave length of 100 yards give or take. Tsunami waves can only be SEVERAL INCHES tall but have a wave length of SEVERAL HUNDRED KILOMETERS!!! This is why the tree large local tsunamis in the last 10 years appear to be several strong surges. These surges are VERY similar to an extreme high tide followed by an extreme low tide in the period of 20 minutes instead of 12 hours. The fuel dock at the Santa Cruz Small Craft Harbor was rising and falling approximately 3 feet.
In many places such as Hawaii and the South Pacific tsunami waves shoot up the base of steep volcanic mountains rising from several miles deep. This creates massive devastation. The Continental Shelf as well as other features off our coast tends to deflect most of the Tsunamis energy.
I am a Captain and Marine Biologist on the Monterey Bay. I know these waters very well. Tsunamis generate very strong and unpredictable currents that can leave you stranded miles out to sea. I STRONGLY DISCOURAGE anybody from following my lead.
Heres a wikipedia link explaining what a tsunami is