Tsunami warnings and watches prompted by a magnitude-8.3 earthquake were canceled from eastern Russia to the South Pacific after experts said there was no longer a threat to coastal areas. U.S. tsunami warning centers announced the cancellations in e-mailed statements as seismologists revised the magnitude of the undersea quake in the northern Pacific from the initial 8.1. The quake struck today off Russia’s Kuril Islands at 8:15 p.m. Tokyo time at a depth of 30 kilometers (19 miles).
Residents of Japanese coastal areas were urged to flee after the country’s meteorological agency said waves up to 2 meters (6.5 feet) high could hit northern and eastern Japan. Waves were detected in northern Japan and measured up to 30 centimeters (1 foot) on the island of Hokkaido, the U.S. Pacific Tsunami Warning Center said. There were no immediate reports of damage or injuries following the earthquake.
A tsunami (pronounced /tsʊˈnɑːmi/ or /sʊˈnɑːmi/) is a series of waves when a body of water, such as an ocean is rapidly displaced on a massive scale. Earthquakes, mass movements above or below water, volcanic eruptions and other underwater explosions, landslides and large meteorite impacts all have the potential to generate a tsunami. The effects of a tsunami can range from unnoticeable to devastating. The term tsunami comes from the Japanese language meaning harbour (“tsu”, 津) and wave (“nami”, 波). Although in Japanese tsunami is used for both the singular and plural, in English tsunamis is often used as the plural. The term was created by fishermen who returned to port to find the area surrounding their harbour devastated, although they had not been aware of any wave in the open water. Tsunamis are common throughout Japanese history, as 195 events in Japan have been recorded.
A tsunami has a much smaller amplitude (wave heights) offshore, and a very long wavelength (often hundreds of kilometres long), which is why they generally pass unnoticed at sea, forming only a passing “hump” in the ocean.
Tsunamis have been historically referred to as tidal waves because as they approach land, they take on the characteristics of a violent onrushing tide rather than the sort of cresting waves that are formed by wind action upon the ocean (with which people are more familiar). Since they are not actually related to tides the term is considered misleading and its usage is discouraged by oceanographers.  Since not all tsunamis occur in harbours, however, that term is equally misleading, although it does have the benefit of being misleading in a different language.