Tsunami protection
Since predicting earthquakes is so hard, tsunami protection relies
on warning systems. These warning systems combine seismographs
with water-based sea level gauges, sea fl oor pressure
sensors and satellite communications, so that when a tsunami
causing earthquake occurs warnings can be provided to coastal
areas as quickly as possible.
How fast can a tsunami reach land?
Courtesy National Oceanic and Atmospheric Agency (NOAA)
This map, from the Pacifi c Tsunami Warning Systen,
shows approximate travel times for a tsunami
generated by an earthquake near Hawaii.
Not all countries are served by warning systems, and even those that are often have trouble getting warnings out to
small or remote communities. In addition, while warnings help save lives, they do not protect land, buildings and
vegetation from the power of massive waves. So, in some places people have taken actions to develop some protection
from the force of the sea. Sea walls, are usually built to prevent coastal erosion, however they might in some
instances help dissipate energy in tsunami waves so that less destruction occurs on land. Natural barriers to water
also help. In the December 2004 tsunami, communities protected by mangrove forest suffered less damage than
those completely exposed to the wave.
The Huu-Ay-Aht people remember the stories the Elders tell about the great wave that nearly wiped them out 300
years ago. They also remeber the tsunami of 1964; their community wasn’t built then, but the nearby town of Bamfi
eld suffered a lot of damage. They are taking steps to protect both themselves and their homes. They have been
negotiating with the Government of British Columbia to move their entire community further away from shore and
onto higher ground. While an agreement hasn’t been reached yet, the Boxing Day tragedy in Asia has reenergized
their efforts.
On April 1, 1946, a magnitude 7.4 earthquake occured off the southern coast of the Aleutian
Islands (just west of Alaska). Although the earthquake was relatively small, it lifted a huge part
of the sea bed and generated a massive tsunami. A 30m wave hit Scotch Gap on Unimak Island
within 45 minutes of the quake, completely destroying a 30m, reinforced concrete lighthouse
located well above sea level. Five hours later, the wave hit Hawaii killing 159 people. It was still
over 15m high when it ran aground in Hilo on the Big Island (shown above). This tsunami was
the impetus for what is now the Pacifi c Tsunami Warning System.
Posted by Aneka Tips
on 17.07. Filed under