What Is A Tsunami? Japan Earthquake In Fukushima Forces Evacuations, Threatens Asia-Pacific With Giant Waves

UPDATE: 3:51 a.m. EST -- All tsunami warnings for Japan’s Pacific coast have been cancelled hours after a magnitude-7.3 earthquake struck eastern Japan Tuesday.

The Japan Meteorological Agency warned that another large quake could be expected within the next few days, and urged residents to “remain cautious” for the next week. So far, only minor injuries in the quake have been reported.

Original story:

A tsunami warning was issued shortly after a magnitude 7.3 earthquake struck eastern Japan Tuesday morning local time. While there were no immediate reports of deaths or serious injuries, local residents were bracing for after effects that are common following such string seismic activity.

One of those after effects that can come after a powerful earthquake near a body of water is a tsunami, which the National Ocean Service defines in part as being a giant wave generated by "earthquakes or volcanic eruptions under the sea." The definition continues:

Out in the depths of the ocean, tsunami waves do not dramatically increase in height. But as the waves travel inland, they build up to higher and higher heights as the depth of the ocean decreases. The speed of tsunami waves depends on ocean depth rather than the distance from the source of the wave. Tsunami waves may travel as fast as jet planes over deep waters, only slowing down when reaching shallow waters. While tsunamis are often referred to as tidal waves, this name is discouraged by oceanographers because tides have little to do with these giant waves.

People in and near the city of Fukushima, the epicenter of Tuesday's earthquake, were told that tsunamis were expected to hit the area "imminently," NBC News reported. They could be as high as 10 feet. "Please evacuate right now," Japan news outlet NHK warned. "Don't stop. Don't try to go back."

One nearly three-foot tsunami had already been reported in the city of Soma, which is in Fukushima Prefecture, according to NHK. The earthquake also forced power outages in the immediate area.

The area was experiencing multiple aftershocks, with one as strong as a 5.3 magnitude, according to the U.S. Geological Survey.

As a result, the country's bullet train service was suspended in eastern Japan by Japan Railways, the Telegraph reported.

While inhabited lands located in the Asia-Pacific were put on alert, there were a number of places where the possibility of a tsunami was ruled out, including Hawaii and New Zealand.

Tuesday's earthquake struck near the same location as another in 2011, when more than 18,500 people were killed from a tsunami following a magnitude-9 quake that forced the Fukushima Daiichi Nuclear Power Station the go through multiple meltdowns.

The tsunami of 2011 reached heights of up to 128 feet and affected as far as 10 miles of land, according to Live Science.

Watch a tsunami live feed of footage from Japan below on an embedded live feed from Fukushima.