The word tsunami is derived from the Japanese word “tsu” and “nami”, meaning “Harbor” and “Wave” respectively.
The speed of tsunami waves depends on ocean depth rather than the distance from the source of the wave. Scientists can predict when a tsunami will arrive at various places by knowing the source characteristics of the earthquake that generated the tsunami and the characteristics of the seafloor along the paths to those places. When the ocean is over 19,685 feet (6,000 m) deep, unnoticed tsunami waves can travel over 500 mph (804.67 kmh). One coastal community may see no damaging tsunami wave activity while in another nearby community destructive waves can be large and violent. Reefs, bays, entrances to rivers, undersea features and the slope of the beach help to modify the tsunami as it approaches the coastline (NOAA).
Dependent on the distance of the tsunami from its source, it may be classified as a:
- Local/near field tsunami A tsunami from a nearby source for which its destructive effects are confined to coasts less than 1 hour tsunami travel time or typically within about 100 km from its source.
- Regional tsunami A tsunami that is capable of destruction in a particular geographic region.
- Destructive tsunami Happens when tsunami waves become extremely large in height, they savagely attack coastlines, causing devastating property damage and loss of life. A small wave only 30 cm high in the deep ocean may grow into a much larger wave 30 m high as it sweeps over the shore.
- Non-Destructive Tsunami Mostly happens as a result of minor earthquakes and/or other events. It can be due to the source being far away from land or the earthquake being too small to have any effect when approaching the shore. When a small tsunami comes to the shoreline it is often seen as a strong and fast-moving tide (Caribbean Tsunami Information Center).
Neno tsunami linatokana na neno la Kijapani <unk>tsu<unk> na <unk>nami<unk>, linalomaanisha <unk>Harbor<unk> na <unk>Wave<unk> kwa mtiririko huo. Kasi ya mawimbi ya tsunami hutegemea kina cha bahari badala ya umbali kutoka kwa chanzo cha wimbi hilo. Wanasayansi wanaweza kutabiri wakati tsunami itafika katika maeneo mbalimbali kwa kujua sifa za chanzo cha tetemeko la ardhi ambalo lilitokeza tsunami na sifa za sakafu ya bahari kando ya njia za kwenda mahali hapo. Wakati bahari iko zaidi ya mita 6,600 kina, mawimbi ya tsunami yanaweza kusafiri zaidi ya kilomita 500 kwa saa. Jamii moja ya pwani yaweza kuona hakuna utendaji wenye kuharibu wa mawimbi ya tsunami huku katika jamii nyingine iliyo karibu mawimbi yenye kuharibu yaweza kuwa makubwa na yenye jeuri. Matofali, mabwawa, viingilio vya mito, vipengele vya chini ya bahari na mteremko wa pwani husaidia kubadilisha tsunami inapoelekea pwani (NOAA). Tsunami inaweza kuonekana kama: (a) Tsunami ya karibu (mwisho wa wiki) au (b) Tsunami ya karibu (mwisho wa wiki) au (c) Tsunami ya karibu (mwisho wa wiki) au (d) Tsunami ya karibu (mwisho wa wiki). - Tsunami ya kikanda Tsunami ambayo ina uwezo wa uharibifu katika eneo fulani la kijiografia. Tsunami ya uharibifu hutokea wakati mawimbi ya tsunami yanapokuwa makubwa sana kwa urefu, yanashambulia pwani kwa ukatili, na kusababisha uharibifu mkubwa wa mali na kupoteza maisha. Wimbi dogo lenye urefu wa sentimita 30 tu katika bahari ya kina kirefu linaweza kukua kuwa wimbi kubwa zaidi lenye urefu wa mita 30 linapopiga pwani. - Tsunami isiyo ya Uharibifu Hasa hutokea kama matokeo ya matetemeko madogo ya ardhi na/au matukio mengine. Huenda ikawa ni kwa sababu chanzo cha tetemeko hilo kilikuwa mbali na nchi kavu au tetemeko hilo lilikuwa dogo sana hivi kwamba halikuweza kuathiri eneo hilo. Tsunami ndogo inapofika kwenye pwani mara nyingi huonekana kama mawimbi yenye nguvu na yenye mwendo wa haraka (Kituo cha Habari cha Tsunami cha Karibea).