Tsunamis in Hawaii

     Tsunamis have been in the news frequently these past couple of years. Any shoreline, any where in the world, is vulnerable to tsunamis. Some shorelines are more prone to these events than others. Hawaii is completely surrounded by water, and is situated in the Pacific ring of fire. While Hawaii is not immune to tsunamis, she does have an incredible early warning system.

     Tsunamis can be triggered by earthquakes, volcanoes erupting, landslides, and meteorites striking the ocean. Not all earthquakes produce a tsunami; in fact, the Big Island of Hawaii has small earthquakes everyday, as the magma under the earth’s crust moves around. These earthquakes rarely have any effect on the waves, because they are generally so small. The earthquakes that cause tsunamis are around subduction zones that are under water. A subduction zone occurs when one of the earth’s plates rides over another plate. The upper plate gets stuck, and doesn’t move smoothly, as the other plate subducts or slides under it. Pressure builds up, and the upper plate slowly rises. At some point, the pressure becomes too great, the upper plate snaps up and over the part of the lower plate, where it gets stuck, and an earthquake results. It is this upward snap that causes the tsunami, as the water over the “snap” area is suddenly forced up. This causes several waves that radiate out from subduction earthquake epicenter.

     These waves rush away from the epicenter at very rapid rates. This is the part of the article that will make you wish you paid better attention in science class in high school. The energy of the “snap” of the earthquake sends the tsunami away from the epicenter at about 500 miles per hour. Because the ocean is so vast, the wave in the deep water is only about a foot higher than normal but the wave length is huge (the distance from wave to wave) as it oscillates. As the tsunami comes into shore, the wave has to slow down. The energy of the wave then changes from a long wave length to very short wave length and the wave height then becomes huge.  

     The Hawaiians have long dealt with tsunamis in their history. There is a memorial in Hilo to the 61 people that lost their lives in a tsunami that came from an earthquake in South America. The wave took about 15 hours to reach the Big Island. The lag time between earthquake and the destruction of the tsunami spurred a quest to develop an early warning system for Hawaii.

     The Pacific Tsunami Warning Center was developed to coordinate efforts to warn all the people in the Pacific Basin of impending tsunamis. The PTWC is the best in the world, and the one that all other warning systems are modeled after. The PTWC issues the watches and warnings for any possible tsunami, and then it is up to the local government to disseminate the information.

     Hawaii has worked diligently to make sure the early warning gets to everyone on the island. The Hawaiian Civil Defense System maintains 365 sirens state wide in addition to announcements on radio, and television to get the early warning out. Homes and businesses alike have weather alert radios that also broadcast the warning. Hawaii also practices tsunami drills which allow every person on the island review their plan for evacuation to higher ground in the event of a tsunami.

     Hawaii has learned to live with the ocean, and be ever vigilant of the dangers that are associated with living on such a beautiful body of water. The Pacific Ocean is so incredibly beautiful in Hawaii; it is hard to remember that it can also be dangerous. The Hawaiians say, “never turn your back to the ocean”, and those are words they live by. The Hawaiian tsunami early warning system is the best in the world, which is a great comfort to those of us who live here or come to play here. Mahalo to all who keep us safe!

http://geology.com/articles/tsunami-geology.shtml

http://www.prh.noaa.gov/ptwc/history.php

http://www.prh.noaa.gov/ptwc/

http://www.pdc.org/iweb/tsunami_zones.jsp