Is the Bay Area susceptible to a tsunami ?

October 20, 9:52 PMSan Jose City Buzz ExaminerShiela Arias

Previous

Comment Print Email RSS Subscribe

Subscribe

Get alerts when there is a new article from the San Jose City Buzz Examiner. Read Examiner.com's terms of use.

Email Address   Include other special offers from Examiner.com Terms of Use

          The tragedy brought about by the Loma Prieta catastrophe is still fresh in the minds of Bay Area residents. And with the onset of natural calamities in other parts of the world, the threat of yet another natural hazard lingers in the mind of not only government leaders and scientists, but likewise in the hearts and minds of ordinary people.

          Devastations caused by tsunamis in far away areas such as the Pacific, particularly Indonesia and American Samoa may not necessarily be limited in the International Rim of Fire, it may likewise affect such famous sites as the U.S. Bay Area.

          But just what is a tsunami and why would Bay Area residents bother to even prepare for it?

A tsunami can travel through the ocean at the speed of a commercial jet and cross the entire ocean in a matter of hours. Tsunamis, pronounced as (soo-NAH-mee) is a Japanese word meaning “harbor wave.” It is a series of ocean waves created by a sudden displacement of seawater. Most tsunamis are generated by earthquakes, landslides, undersea slumps or meteor impacts. Waves radiate outward in all directions from the disturbance and can propagate across entire ocean basins.

          The tsunami waves are distinguished from ordinary ocean waves by their great length between peaks, often exceeding 100 miles in the deep ocean and by the long amount of time between these peaks, ranging from five minutes to an hour. The speed at which tsunamis travel depends on the ocean depth. A tsunami can exceed 500 miles per hour in the deep ocean but slows to 20 to 30 miles per hour in the shallow water near land.

          In the deep ocean, a tsunami is barely noticeable and will only cause a small and slow rising and falling of the sea surface as it passes. But when it approaches land, it becomes a hazard. As the tsunami approaches land and shallow water, the waves slow down and become compressed, causing them to grow in height.

          The recent tsunami in Indonesia and American Samoa focused world attention on this rare but very real threat and the need for a comprehensive warning system.      

At the helm of an effective detection and warning system is the National Oceanographic Atmospheric Administration’s Tsunami Warning System which provides a 24-hour detection warning system that increases public awareness about the threat of tsunamis. NOAA started developing the tsunami warning system in 1946 when Hawaii was struck by a tsunami originating from the Aleutian Islands. It established the Richard Hagemeyer  Pacific Tsunami Warning Center in 1949 and the West Coast/Alaska Tsunami Warning Center in Alaska in 1967 which are responsible for issuing tsunami

Advisories, watches, warnings and information messages to emergency management officials and the public. Aside from that, the Pacific Tsunami Warming Center serves as the operational center for the Pacific which comprises 26 member nations of the Pacific Rim where most tsunamis occur.

            NOAA has warning centers that use an extensive network of Deepocean Assessment and Reporting of Tsunamis (DART) stations and sea-level gauges to determine if a tsunami has been generated. These stations provide real-time detection as waves travel across the open ocean. Each DART consists of a bottom pressure sensor anchored to the seafloor and a companion moored surface buoy.

An acoustic link transmits data from the bottom pressure sensor to the surface buoy and satellite links then relay the data to ground stations and then to the tsunami warning centers for action within a matter of seconds.

NOAA has also developed tsunami impact forecast models for major U.S. coastal communities including the Bay Area at high risk for tsunamis. The models are used to create inundation and evacuation maps for emergency managers in the event of a tsunami.

An effective tsunami warning system includes hazard detection, risk assessment, warning dissemination and a public that understands what to do when a warning is sounded. NOAA has led the U.S. effort to build a comprehensive tsunami warning system wherein the result is a nation better equipped to detect a tsunami and alert communities of the impending danger.