When is a Tsumani not a Tsunami?

When is a Tsumani not a Tsunami? was Originally Posted on November 3, 2009 by lavarock

When is a Tsunami not a Tsunami? When it is a drill.

Yesterday a mass evacuation drill took place on the Hilo side of our island. Over 800 children walked to the Hilo Airport (where flights had been suspended) and then the children were loaded into waiting school busses. The drill happens yearly, however the children must make the walk only once every 3 years.

We have recently had three tsunami watches but no actual waves to be concerned with and often these watches are cancelled hours before any wave would strike. being situated in the middle of the Pacific, the possibility of a tsunami is ever present. Over time we have had a few disastrous strikes here. In the 20th century an estimated 221 people died; more than any other local disaster.

In 1946 a 7.1 earthquake in the Aleutian Islands created a tsunami which hit the Big island on April 1st. Hilo was the hardest hit with $26 million dollars in damage and 159 deaths.

In 1952 a tsunami was generated in the USSR. No lives were lost here but an estimated $1 million dollars in damages was noted.

In 1957 an 8.3 quake in the Aleutians created a tsunami, which hit here. The wave was 24 foot elsewhere and 12 foot here. $5 million dollars damage here was noted.

In 1960 an 8.3 quake in Chile created a 35-foot wave in Hilo causing $23 million dollars damage and causing 61 deaths.

In 1975 a local earthquake off the Big Island killed 2 campers and injured 19. The first wave was 5 feet tall but the second was 26 feet.

In 2006, the Big Island experienced a 6.8 earthquake followed soon thereafter by a 6.3 quake. These quakes were centered about 14 miles from shore and just north of Kailua-Kona. These two massive quakes did not create a tsunami! I understand that since the quake was well below the surface and so close to land, there was no space to create the wave.

As you may know, these tsunamis are not giant “tidal waves” shown in movies that tower over giant ships and can be seen approaching land, but rather a pressure wave under water that draws water from the shore and then pushes massive amounts of water back onto the shore.

Living like a target in the middle of the Pacific is a strange feeling. You hope that a local quake will not create a wave because it would appear almost instantly. Thus if you were at the shore and felt an earthquake you would immediately head away from the water ASAP. Our coast is very rocky and it might not be easy to immediately run, but in most cases, you would not have to travel far to be well above the danger line.

In current times, we have created a field of buoys spanning the Pacific to tell us of impending tsunamis. We have sirens along the coasts and the telephone books contain maps of evacuation areas. Luckily the island rises quickly from the ocean and thus sometimes 500 feet from the ocean you would be above water levels. In most cases, driving 5 minutes puts you out of danger.

Recent tsunami watches have been more than 4 hours of prior warning because the earthquakes are so far from us.

So, although tsunamis are an ever-present danger to those of us who have chosen to live in “paradise”, we know that we will probably have many hours advance notice and are pretty well prepared.