There are three (3) broad types of tsunamis:
This is a tsunami where its destructive effects are experienced on coasts within 100 km from the source of the tsunami. In such cases, the travel time for the tsunami is generally less than one (1) hour.
A local tsunami is usually generated by an earthquake, but can also be caused by a landslide or a pyroclastic flow from a volcanic eruption.
Locally generated tsunamis are especially dangerous. This type of tsunami may reach a nearby shore in less than ten minutes. In such cases, there is not sufficient time for a Tsunami Warning Center or for local authorities to issue an official tsunami warning. Coastal residents and users should therefore take life-saving action as indicated on the sign based on the shaking of the ground, which is a warning that a tsunami may be imminent.
A tsunami capable of destruction in a particular area which lies between 100 km - 1,000 km form the source of the tsunami. Regional tsunamis can take between 1-3 hours to reach the affected shoreline.
The most destructive tsunamis can be classified as local or regional.
Also referred to as a tele-tsunami or ocean-wide tsunami, distant tsunamis originate from a far away source (more than 1000 km away) and generally take more than 3 hours to arrive at affected coasts.
When a tsunami is formed, the waves generally radiate and move in opposite directions. In this case, a local tsunami can impact on coastlines which are close to the tsunami source. The waves which are moving in other directions away from the source of the tsunami, can continue to travel across entire ocean basins as distant tsunamis with sufficient energy to cause additional casualties and destruction on far away shores.
These types of tsunamis allow more time for the Warning Centre to collect data and issue precise bulletins, and for local officials to communicate warning information and alert the vulnerable populations.
|One of the documented distant tsunamis to affect the Caribbean impacted on November 1, 1755. This tsunami was caused by the 8.7 magnitude Great Lisbon Earthquake in the Azores fracture zone (near Portugal). This tsunami crossed the Atlantic and was observed throughout the region from Barbados to Antigua and as far west as Cuba. Waves some 2-10m high were generated and continued to arrive for many hours. Luckily, no damage or casualties were reported. The concept of the Cartoon Warning Booklet is based on this event.
|For more information
|Tsunami Warning! Cartoon Storybook (3.48 MB)||