Japan has marked two years since the devastating earthquake and tsunami that killed more than 18,000 people and triggered a nuclear crisis.
The magnitude 9.0 earthquake sent waves up to 40 metres high slamming into the country's north-west coast on 11 March 2011, crippling the Fukushima nuclear plant.
The government hosted a national ceremony in Tokyo to mourn 15,881 people known to have died and 2,668 others who remain unaccounted for. Emperor Akihito and Empress Michiko attended.
They observed a moment of silence at 2:46pm on Monday, the time the earthquake struck off the north-eastern Pacific coast, AFP reports.
The earthquake destroyed or damaged 1 million homes. Two years on, more than 300,000 Japanese are still in temporary housing.
Tsunami-hit communities are divided among those who want to rebuild on land that may have been in the family for generations and those who want to move their town to higher, safer ground.
Complications associated with stressful living conditions have killed 2,303 survivors of the quake and tsunami, government figures show. Domestic violence and depression are increasingly noted as problems in some communities.
Nearly 10,000 aftershocks have been recorded since the original quake, some shaking the ground at the Fukushima plant where the damaged reactors remain dysfunctional.
The government says the Fukushima plant is stable and no longer releasing radioactive materials. It says food products from the region are checked for radioactive contamination before being shipped to markets.
Despite reassurances, many consumers avoid Fukushima produce fearing it is contaminated, dealing another blow to the region's already-faltering farming industry.
Effects felt in space - scientists
The massive quake was so big it sent a ripple of sound through the atmosphere that was picked up by an orbiting satellite, scientists say.
The BBC reports the satellite's instrumentation was able to detect the disturbance as it passed through the thin wisps of air still present 255 kilometres above the earth.
The observation is reported in the journal Geophysical Research Letters.
It has long been recognised that major quakes will generate very low-frequency acoustic waves, or infrasound - a type of deep rumble at frequencies below those discernible to the human ear.
But no spacecraft in orbit has had the capability to record them, until now.
On Sunday, thousands of protesters observed the anniversary by marching in Tokyo urging an end to the use of nuclear power, the BBC reports.
Japan's 50 nuclear reactors were shut down for checks after the earthquake and only two have since been turned on again.
But Prime Minister Shinzo Abe, who was elected in December, has indicated he wants to restart the reactors after safety checks to meet pressing power needs.