There is no tsunami season. An earthquake or landslide anywhere in the Pacific can generate tsunami waves that can travel across the ocean at more than 500 miles per hour. In Hawai'i, we also can experience locally generated tsunami, especially from the direct results and side effects of our active volcanoes.
There is no average or normal tsunami. There is usually more than one wave and the first is not always the worst. The tsunami can last for hours, with waves typically spaced from 10 to 60 minutes (5 to 90 minutes possible).
Tsunami are not just big surf. These waves are not tidal waves and do not result from offshore storms as many of our high surf surges do. They are not good for surfing!
You cannot outrun a wave.
Sometimes the water recedes making beachcombing very tempting. But when
the wave comes, it comes fast!
For those who don't know.....
A tsunami (pronounced tsoo-NAH-mee) is a wave train, or series of waves, generated in a body of water by a pulsating or abrupt disturbance that vertically displaces the water column. Earthquakes, landslides, volcanic eruptions, explosions, and even the impact of cosmic bodies, such as meteorites, can generate tsunamis. Tsunamis can savagely attack coastlines, causing devastating property damage and loss of life.
Tsunamis are often called "tidal waves" as they may resemble a non-lunar-tidal rush of rapidly rising water, rather than big cresting waves reaching the shore. However, the term is discouraged by oceanographers since tsunamis are not related to tides.
The term "tsunami" comes from the Japanese tsu (harbor) and nami (wave).
Causes
Tsunamis are unlike wind-generated waves on a local lake or at a coastal beach, in that they are characterized as shallow-water waves, with long periods and wave lengths. The wind-generated swell one sees at a surf beach, for example, spawned by a storm out in the pacific and rhythmically rolling in, one wave after another, might have a period of about 10 seconds and a wave length of 150 m. A tsunami, on the other hand, can have a wave length in excess of 100 km and period on the order of one hour.
As a result of their long wave lengths, tsunamis behave as shallow-water waves. A wave becomes a shallow-water wave when the ratio between the water depth and its wave length gets very small. Shallow-water waves move at a speed that is equal to the square root of the product of the acceleration of gravity (9.8 m/s/s.... hey, that's meters per second squared.... I bet Ms. Goth 'Genius' Daughter..knew that!) and the water depth - let's see what this implies: In the Pacific Ocean, where the typical water depth is about 4000 m, a tsunami travels at about 200 m/s, or over 700 km/hr. Because the rate at which a wave loses its energy is inversely related to its wave length, tsunamis not only propagate at high speeds, they can also travel great, transoceanic distances with limited energy losses.
Tsunamis
can be
generated when the sea floor abruptly deforms and vertically displaces
the overlying water. Tectonic earthquakes are a particular kind of
earthquake that are associated with the earth's crust deformation; when
these earthquakes occur beneath the sea, the water above the deformed
area is displaced from its equilibrium position. Waves are formed as
the displaced water mass, which acts under the influence of gravity,
attempts to regain its equilibrium. When large areas of the sea floor
elevate or subside, a tsunami can be created.
