Japan's northeastern coast was a swampy wasteland of damaged houses, overturned cars, sludge and dirty water today as the nation awoke to the devastating aftermath of one of its greatest disasters, a powerful tsunami created by one of the strongest earthquakes ever recorded.
The death toll from Friday's massive magnitude 8.9 quake stood at more than 400 but was expected to exceed 1,000 once disaster response teams could reach the hardest-hit areas and assess casualties, the National Police Agency and Defense Ministry said.
Authorities declared a state of emergency for five nuclear reactors at two quake-stricken power plants as military and utility officials scrambled to tame rising pressure and radioactivity levels inside the units and stabilize the facilities used to cool the plants' hot reactor cores. Thousands of nearby residents were forced to evacuate.
The earthquake that struck off the northeastern shore was the biggest recorded quake ever to hit Japan. It ranked as the fifth-largest earthquake in the world since 1900 and was nearly 8,000 times stronger than one that devastated Christchurch, New Zealand, last month, scientists said.
Chief Cabinet Secretary Yukio Edano said an initial assessment found "enormous damage," adding that the Defense Ministry was sending troops to the hardest-hit region.
President Obama pledged U.S. help following what he called a potentially "catastrophic" disaster. One U.S. aircraft carrier is already in Japan, and a second was on its way, he said. A U.S. ship was also heading to the Marianas Islands to assist, he added.
The United States Geological Survey said another strong earthquake struck just before noon today in the sea in virtually the same place where Friday's quake originated.
Today's magnitude 6.8 quake was followed by a series of temblors from the same area, the USGS said. It was not immediately known whether the new quakes caused any more damage. All were part of the more than 125 aftershocks.
The official death toll stood at 413, while 784 people were missing and 1,128 injured. In addition, police said between 200 and 300 bodies were found along the coast in Sendai, the biggest city in the area of the quake's epicenter. An untold number of bodies were also believed to be lying in the rubble.
The entire Pacific had been put on alert -- including coastal areas of South America, Canada and Alaska -- but waves were not as bad as expected.
The offshore quake struck at 2:46 p.m. local time.
The quake shook dozens of cities and villages along a 1,300-mile stretch of coast and tall buildings swayed in Tokyo, hundreds of miles from the epicenter. Prime Minister Naoto Kan was addressing parliament at the time.
Minutes later, the earthquake unleashed a 23-foot-high tsunami that washed far inland over fields and smashed towns.
Large fishing boats and other vessels rode the high waves ashore, slamming against overpasses or scraping under them and snapping power lines along the way. A fleet of partially submerged cars bobbed in the water. Ships anchored in ports crashed against each other.
The tsunami roared over embankments, washing anything in its path inland before reversing direction and carrying the cars, homes and other debris out to sea. Flames shot from some of the homes, apparently from burst gas pipes.
Waves of muddy waters flowed over farms near Sendai, carrying buildings, some of them ablaze. Drivers attempted to flee. The tarmac at Sendai's airport was inundated with thick, muddy debris that included cars, trucks, buses and light planes.
Highways leading to the worst-hit coastal areas buckled. Telephone lines snapped. Train service was suspended in northeastern Japan and in Tokyo, which normally serves 10 million people a day. Untold numbers of people were stranded in stations or roaming the streets. Tokyo's Narita airport was closed indefinitely.
Most trains in Tokyo started running again today.
A ship with 80 dock workers was swept away from a shipyard in Miyagi prefecture. Everyone on the ship was believed to be safe, although the vessel had sprung a leak and was taking on water, Japan's coast guard said.
In the coastal town of Minami-soma, about 1,800 houses were destroyed or damaged, a Defense Ministry spokeswoman said. Fire burned well past dark in a large section of Kesennuma, a city of 70,000 people in Miyagi.
Japan declared its first-ever states of emergency for five nuclear reactors at two power plants after the units lost cooling ability in the aftermath of the earthquake, and workers struggled to prevent meltdowns.
The earthquake knocked out power at the Fukushima Daiichi plant, and because a backup generator failed, the cooling system was unable to supply water to cool the 460-megawatt No. 1 reactor. Although a backup cooling system is being used, Japan's nuclear safety agency said pressure inside the reactor had risen to twice the level considered normal.
Authorities said radiation levels had jumped 1,000 times normal inside Unit 1 and were measured at eight times normal outside the plant. They expanded an earlier evacuation zone from 2 miles to 6.2 miles. About 3,000 people were urged to leave their homes in the first announcement.
Tokyo Electric Power Co. warned of power shortages and an "extremely challenging situation in power supply for a while."
The utility, which also operates reactors at the nearby Fukushima Daini plant, later confirmed that cooling ability had been lost at three of four reactors there, as well as a second Fukushima Daiichi unit. The government promptly declared a state of emergency there as well.
Nearly 14,000 people living near the two power plants were ordered to evacuate.
The radiation level outside the 40-year-old plant Daiichi Unit 1 in Onahama, a city about 170 miles northeast of Tokyo, is still considered very low compared with the annual exposure limit, said Ryohei Shiomi, an official with the Japan Nuclear and Industrial Safety Agency. It would take 70 days of standing at the gate to reach the limit, he said.
The Defense Ministry said it had sent troops trained to deal with chemical disasters to the plants in case of a radiation leak.
A large fire erupted at the Cosmo oil refinery in the city of Ichihara and burned out of control with 100-foot flames whipping into the sky.
Japanese automakers Toyota, Nissan and Honda halted production at some assembly plants in areas hit by the quake.