A tsunami is a set of ocean waves caused by any large, abrupt disturbance of the
sea surface. If the disturbance is close to a coastline, local tsunamis can demolish
nearby coastal communities within minutes. A very large disturbance can cause
local devastation and export destruction thousands of miles to distant coastal
communities. A major tsunami can bring destruction to the coastal residents of an entire ocean, making the hazard inherently international. The word tsunami is
Japanese, represented by two characters: tsu, meaning ‘harbour’, and nami,
meaning ‘wave’. It is thought that from ancient times, when the Japanese
observed unusual wave activity in a harbour, they were aware that a tsunami
could be approaching. Tsunamis rank high on the scale of natural disasters. Since
1850 alone, tsunamis have been responsible for the loss of over 420 000 lives and
billions of dollars of damage to coastal structures and habitats throughout the
world. Most of these casualties were caused by local tsunamis that occur about
once per year somewhere in the world. Predicting when and where the next
tsunami will strike is currently impossible. Once generated, however, forecasting
tsunami arrival and impact is possible through modelling and measurement
technologies.