(CNN) -- Within an hour after a major earthquake rattled Japan, the nation and the world watched a surreal and unprecedented scene from a helicopter hovering above the coastal area of Miyagi prefecture:

Neat rows of tilled farmland being cleaved by a wall of water, with a white ship sweeping across the soil . Behind it, a massive wave of mud, debris and burning buildings atop the rushing water.

"We've never seen this -- we're watching a live tsunami strike Japan," said CNN International meteorologist Ivan Cabrera. "Those are not taped pictures, that appears to be live pictures of a major tsunami strike the coast."

Tokyo residents shook off the horror of the 8.9-magnitude earthquake only to watch on television as the first tsunami waves crashed into coastal areas hundreds of miles northeast of the city.

"The footage that we're seeing, the video that we're seeing on the television screens is absolutely heart wrenching," said Matt Alt, a Tokyo resident. "Because you know a lot of those people did not have a chance to evacuate before the wave hit, even though they were telling you need to get away from the shore lines.

"Just watching this wave hit and cars and buildings and houses being spent away, I think we're going to see a significant number of casualties," Alt said. So far the number of casualties is not known.

In Japan, one of the most wired nations in the world, the reaction was immediate . Twitter use skyrocketed, with tweets coming out of Tokyo topping 1200 per minute, according to Tweet-o-Meter, a traffic-monitoring system at University College of London.

The temblor was the most powerful on record in earthquake-prone Japan, government officials said. In Tokyo, traffic, trains and power shut down and air traffic halted, created an eerie scene on the streets of one of the world's largest cities as people stood outside and wondered what to do.

"This is a city of 13 million people that's paralyzed," said Kyung Lah, CNN Tokyo correspondent. "It's going to be a big long challenge for us tonight in Tokyo."