The only reason to have an explanation would be if the German and English meaning/use differed, i.e. if "der Tsunami" was
only used to describe a tsunami in the Pacific in German (but not in English), as the dictionaries actually seems to suggest:
Tsu|na|mi, der; -, -s [jap. tsunami, eigtl.= Hochwasser]:
durch Seebeben ausgelöste Flutwelle im Pazifischen Ozean: Riesenwellen, so genannte -s, haben die Gestalt der Küsten stärker modelliert als bislang angenommen (Spiegel 44, 1992, 327); Das Katastrophengebiet, wo der T.... ein Dutzend Fischerdörfer dem Erdboden gleichmachte oder schwer verwüstete (MM 22.7. 98, 13).
© 2000 Dudenverlag
Bertelsmann disagrees that it's only caused by earthquakes, but agrees that it is in the Pacific:
Aus: BERTELSMANN Wörterbuch
Tsu|na|mi [m. -; -s] unvermittelt auftretende,
durch unterschiedliche geologische Aktivitäten des Meeresbodens ausgelöste Meereswelle des Pazifik, die die Küstengebiete flutartig überschwemmt [
... as does Wahrig:
Aus: WAHRIG Rechtschreibung
Tsu|na|mi m. Gen.- Pl. -s
von Seebeben hervorgerufene Flutwelle des pazifischen Ozeanscompare:
tsunami noun (tsunamis) a type of fast-moving and often very destructive high wave caused by some form of movement in the Earth's surface, eg a volcanic eruption, landslide, etc. Sometimes referred to as a tidal wave although it is not associated with the tides.
ETYMOLOGY: 19c: Japanese, from tsu harbour + nami wave. (Chambers)
A long high undulation or series of undulations of the surface of the sea caused by an earthquake or similar underwater disturbance, travelling at great speed and in shallow waters often building up enough height and force to flood the land. Also called seismic sea- wave, tidal wave. (New Shorter OED)
: a great sea wave produced especially by submarine earth movement or volcanic eruption
http://www.merriam-webster.com/dictionary/tsunami(No mention of the Pacific Ocean in the English dics)
Are these simply wrong or misleading? A Google search shows quite a few German sites about tsunamis in the Atlantic, but maybe those are technically wrong / they are aimed at non-professionals / the meaning is changing??