Nearly half a million people have been forced to flee their homes and are in desperate need of aid.
Wastelands of mud and debris now stretch along Japan's northeast coast where towns and villages used to be, and the search for the missing and the dead continues. Here is the situation Japan faces:
More than a quarter of evacuees are from the areas surrounding the Fukushima nuclear power station, north of Tokyo. Across the nation, 1.4 million people are without water and 2.5 million have no power.
With more than 12,000 buildings destroyed, more than 215,000 people were in 1350 emergency shelters at the weekend, many huddling over heaters in freezing conditions at night, the National Police Agency said.
Although the Government doubled the number of soldiers deployed in the aid effort to 100,000, Prime Minister Naoto Kan called on his people to come together as they faced their darkest days.
Describing the disaster as unprecedented, he added: "I want the people to overcome this quake ... by using the strengths of each of you, together" with emergency workers.
The Bank of Japan will today pledge to supply as much money as needed to prevent a financial crisis. Japan cannot cut its interest rates - they are already low, at 0-0.1 per cent.
The area hit by the quake is home to factories of big manufacturers such as Toyota, and many have halted operations.
The bank's priority is to ensure commercial banks in quake-struck regions do not run out of cash in case of "runs" by customers. It will likely do this by extending loans under more flexible conditions than usual.
The central bank will also provide 2 trillion to 3 trillion yen (almost $50 billion) in funds through its market operation this morning, two to three times the normal amounts, to soothe markets.
New Zealand has sent an Urban Search and Rescue team in a move Prime Minister John Key said recognised the support the earthquake and tsunami-ravaged country gave to Christchurch.
The first of the 48-strong team - one third of all New Zealand personnel - arrived at Tokyo's Narita Airport yesterday afternoon and are expected to stay in Japan up to three weeks.
Much of Japan's own 120-member team left Christchurch on Saturday to be sent straight in to their own country's disaster zones.
About 60 other international teams are on alert to assist Japan if needed, the United Nations said.
The United States aircraft carrier USS Ronald Reagan arrived off the coast of Japan early yesterday to provide logistical support for Japanese military forces.
Japan has asked the carrier to refuel its helicopters and help transport its troops to affected areas.
A 144-member rescue team of the US Agency for International Development was also due at Misawa in northern Japan yesterday to join inland operations.
Australian Foreign Minister Kevin Rudd said self-contained field hospitals and disaster victim identification teams had been offered to help in rescuing survivors and recovering bodies.
And the US Nuclear Regulatory Commission said two of its experts were headed for Japan.
The death toll from the earthquake and tsunami could top 10,000 in one prefecture alone, police say.
Estimates so far put more than 1800 people as likely to have been killed or missing, according to Kyodo news agency.
Miyagi police spokesman Go Sugawara said yesterday that the prefecture's police chief told a gathering of disaster relief officials his estimate for deaths in the prefecture was more than 10,000.
There were only 379 officially confirmed deaths in Miyagi out of a total of 801 as of yesterday evening (NZT).
Japan's Meteorological Agency upgraded the magnitude of the quake to 9.0, up from 8.8.
The quake was already the biggest to hit Japan since record-keeping began in the late 1800s and one of the biggest recorded in the world.
The agency warned yesterday of more strong aftershocks after the quake, which unleashed massive tsunamis in northern Japan.
The US Geological Survey, which has yet to change its estimate of magnitude 8.9, said the quake appeared to have moved Honshu, the main island, by about 2.4m.
The earthquake may also have shortened the length of a day on Earth by a fraction by shifting how the planet's mass is distributed, according to a geophysicist.
Richard Gross, of Nasa, calculated that the earthquake accelerated the Earth's spin, shortening the length of a day by 1.6 microseconds - a microsecond is one millionth of a second.
A 10m tsunami, which followed the quake, travelled at 800km/h at sea and slowed to 100km/h when it washed across the land - reaching as far as 10km inland.
It hit more than 2100km of coastline, which is 500km more than the length of New Zealand (1600km).
The earthquake and tsunami have proven once again how the internet offers an information lifeline to the world in a time of crisis.
On Saturday, nearly five million people watched one raw, unedited YouTube video of the wave chewing away at Japan's coastline. Several other videos had notched up between three and four million hits.
And the internet also functioned as a virtual crisis centre as sites such as Google's people finder service helped locate loved ones and offered help and support to survivors.