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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