Monitoring - and its Flaws
Opened
in 1949, the Pacific Tsunami Warning Center (PTWC), located at Ewa
Beach, Hawai'i, has monitored tsunamis. It is one of only two such
centers in the United States.
Since the creation of the Tsunami Warning System in 1948, Hawai'i
has experienced 20
warnings that have resulted in evacuations of coastal areas. Of
these 20 warnings, 15 have
been considered 'false' because no damaging tsunami occurred. A
study conducted by the
State of Hawai'i after the May 1986 false alarm estimated the cost
of lost business productivity
to be between $30,000,000 and $40,000,000. Not only are these false
alarm evacuations
costly, they also erode the credibility of the emergency management/
tsunami warning system. Furthermore, the fear and disruption of
a false alarm can itself put a population at physical risk; fatalities
and injuries have occurred during an evacuation to such things as
heart attacks and accidents.
The cost of failing to evacuate for a real event or incorrectly
estimating the risk can be much greater. On April 1, 1946, 159 people
died in Hawai'i from a tsunami that originated in Alaska. The City
of Crescent City was successfully evacuated before the first waves
arrived. However, some people reentered the evacuated area after
it receded and 11 were killed by subsequent waves.
Only Hawai'i possesses a set of evacuation maps for the distant
tsunami scenario. These maps were derived from tsunami inundation
and are published in local telephone directories. Once a warning
is received in Hawai'i, residents are evacuated from potential tsunami
inundation areas. The other affected states have no similar maps.
The 1960 Tsunami, Hilo Bay
On
May 23, 1960, a tsunami destroyed much of downtown Hilo.
The quake that caused the 1960 tsunami occurred off the
west coast of South America and
had a magnitude between 8.25 and 8.5. The waves reached
the Hawai'ian Islands in about
15 hours. This tsunami caused little damage elsewhere in
the islands, but the Hilo Bay area was hard hit. 61 people
lost their lives and about 540 homes and businesses were
destroyed or severely damaged. The wave heights in Hilo
Bay reached 35 feet compared to only 3 - 17 feet elsewhere.
The water washed as far inland as Kilauea Avenue/ Keawe
Street through the entire present downtown area and to Kekuanaoa
Street near Kilauea Avenue.
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