Quote:
Originally Posted by DavidMn
Ok mr David, I have a question for you. I know most Tsunami's like the one in Indonesia are low to the groung when they reach shore. What conditions would it take for a the Tsunami wave to be very tall when it reaches shore?
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Hi, Dave. You talking about wave height/amplitude? Tsunamis can surge ashore like a quickly rising tide, but they can also build into a very high wall of water. The shape of the surge is very complex & depends on many, many factors, such as the shape of the sea bed directly offshore (what they call bathymetry), the slope of the continental shelf (shallow or steep), & the shape of the shoreline itself (narrow inlets & bays -- like Hilo in Hawaii -- tend to focus the energy into "small" & "tall").
There were spots in Sumatra where the 2004 tsunami towered to a height of about 70 or 80 feet, because the bathymetry & shoreline funneled the water into a greater height than at most other areas.
Shorelines are mapped with computers in the United States & Japan in order to show potential wave heights at various spots along the coast. You can actually get copies of these maps (usually called inundation or runup maps) from city & county emergency organizations. Various states, including Washington, Oregon, & California, have them compiled.
Here's some info on inundation mapping:
http://nctr.pmel.noaa.gov/inundation_mapping.html