Day 1 – Friday, March 11
- At 2:47 p.m. local time, Japan is struck by the largest recorded earthquake in its history off the coast of the northeastern city of Sendai. Meteorologists log it at 8.9 on the Richter scale.
- 11 nuclear reactors shut down automatically.
- A powerful tsunami triggered by the earthquake sweeps away cars and homes and knocks out regular and backup cooling systems at the six-reactor Fukushima Daiichi nuclear power plant. Several reactors are affected.
- The government orders everyone within a three kilometer radius of the plant to leave the area.
- Japanese authorities report that a fire at the Onagawa nuclear power plant is extinguished.
Day 2 – Saturday, March 12
- A blast caused by a pressure buildup blows the roof off the containment structure of the Fukushima Daiichi plant's Unit 1 reactor, but reports say the nuclear fuel rods are not affected. Four workers are reported injured.
- Residents within a 6-mile radius of the plant are evacuated. Kyodo news agency estimates that 20,000 people are being evacuated.
- Workers begin injecting seawater and boric acid into the reactors in what experts say is a last-ditch attempt to prevent a meltdown after the backup cooling systems for reactors 1 and 3 fail completely.
Day 3 – Sunday, March 13
- Fukushima reactor No. 3 is vented again.
- There is believed to have been a partial meltdown in the reactor.
- A company spokesman states that the radiation released thus far does not pose a health risk to humans.
- The cooling system in reactor 2 fails and more radioactive steam is released.
- The government evacuates more than 200,000 residents from homes within a 20-kilometer (12.4-mile) radius of the plant and tests 160 people for radiation exposure, authorities said Sunday.
- IAEA rates the accident as a level four out of seven on the scale of international nuclear disasters. Three-Mile-Island was rated a five, Chernobyl a seven.
- Meanwhile, in southwestern Japan, Shinmoedake volcano erupts for the second time in 2011, sending ash and rock more than two miles into the air. Analysts say it was the biggest volcanic activity there in 52 years.
Day 4 – Monday, March 14
- An explosion caused by pressure buildup blows away the roof and walls of the building housing the Fukushima Daiichi plant's No. 3 reactor and injured 11 people. The plant's No. 2 reactor loses its cooling capabilities after the explosion. Workers begin injecting seawater and boric acid into that reactor.
- A fire is extinguished, but Chief Cabinet Secretary Yukio Edano says that more radiation was released as a result and that "now we are talking about levels that can damage human health."
- The US Geological Survey upgrades the earthquake from an 8.9 to a 9.0.
Day 5 – Tuesday, March 15
- An explosion hits Fukushima Daiichi's No. 2 reactor in the morning. Readings indicate some damage to the No. 2 reactor's suppression pool, a donut-shaped reservoir at the base of the reactor's containment vessel.
- A fire is ignited in the No. 4 reactor building Tuesday, but is later put out, according to officials.
- The plant is emitting as much radiation in one hour as it normally would in six months, but government spokesman Yukio Edano says: "The possibility that a large amount of radiation has been released is low."
- The head of France's Nuclear Safety Authority, upgrades the international alert from a level 4 disaster to a level 6 incident.
- Foreign companies begin to order evacuations of their employees.
Day 6 - Wednesday, March 16
- A fire breaks out at the building housing the No. 4 reactor. It's believed to be the same spot where a fire broke out Tuesday.
- The roof of reactor No. 4 is believed to be cracked.
- Japan suspends operations at Fukushima after a surge in radiation makes it "too dangerous for workers to remain at the facility."
- After a brief suspension, workers are allowed back on site.
- Japan's emperor makes a rare national appearance, officials say it is his first ever TV appearance
- Nuclear Regulatory Commission Chairman Gregory Jaczko indicates in remarks to a House committee that the US believed the damage at the Fukushima Daiichi nuclear power complex was even graver than Japanese officials had outlined in public.
Day 7 - Thursday, March 17
- The US ambassador in Japan issues a statement to American citizens living within 50 miles of Fukushima to evacuate.
- Workers begin to try to use a water cannon to blast water into the No. 4 building.
- US authorizes voluntary departure from Japan of family members of diplomatic staff, and later US citizens.
- Three out of the six reactors at Fukushima are relatively stable, say officials.
- TEPCO said it has started work to connect outside power cables to the plant and that electricity could be connected soon.
- Japan nuclear agency says pool for cooling spent nuclear fuel at No. 4 building remains "serious concern."
- The national Meteorological Agency reports that the highest tsunami wave on March 11 was 15 meters high in Mekawa, Miyagi.
Day 8 - Friday, March 18
- Japan's nuclear agency upgrades the incident level at Fukushima up from level 4 previously on a 1-7 scale, joining France's Nuclear Safety Authority's assessment, citing reactors No. 2 and No. 3 reactor as the most problematic.
- At 2:46 local time, exactly one week after the earthquake struck, people across the nation observed a minute's silence.
- The IAEA reports that it has NOT received any notification from the Japanese authorities of citizens sickened by radiation contamination.
Day 9 - Saturday, March 19
- Electricity is restored at the Fukushima Daiichi Power Plant.
- Engineers are still working to restore power supplies to the plant's cooling systems.
- There is water in the storage pool of unit 4.
- Power has been recovered for units No. 5 and No. 6 and so has the cooling capability.
- There are no major changes in other reactors (units 1-3).
- Food contamination in spinach from Ibaraki prefecture, and milk from Fukushima prefecture was reported. Authorities say there is no immediate risk.
- Shortages of fuel and vehicles, along with damaged infrastructure are hampering relief operations.
- Some 2.3 million are without water in 12 prefectures.
Day 10 - Sunday, March 20
- Engineers are still working to restore power supplies to the Fukushima's cooling systems.
- The Government has requested that the housing industry construct 30,000 homes for the displaced
- Pressure at reactor 3, reported to rise and was subsequently reported to stabilize.
Day 11 - Monday, March 21
- Electricity has been restored to three reactors at the Fukushima Nuclear Power Plant.
- the cooling systems at the plant are not yet operating.
- Some workers at the facility were temporarily evacuated after gray smoke was seen rising from reactor No 3.
- White smoke was seen later rising from reactor No. 2.
Day 12 - Tuesday, March 22
- Japan officials test nuclear radiation levels of sea water near Fukushima, no immediate health risk, they say.
- Engineers at Fukushima have reconnected all six reactors to the electrical grid.
- Power is restored to the control room of reactor No. 3
- Early reports indicated that reactor No. 1 was receiving power.
- Government of Japan bans the sale of some vegetables from prefectures close to Fukushima
Day 13 - Wednesday, March 23
- Gray smoke is seen coming from reactor No. 3 again
- Workers temporarily halt repair work at Fukushima for the second time this week.
- Power is restored in the control rooms at reactor No. 1, 2, 3, and 4, says TEPCO.
- Reactors 5 and 6 are reportedly cooled to safe levels after their shared diesel generators is repaired.
- Tokyo warns that infants should not drink city tap water because radioactive iodine found in it exceeds legal limits for babies.
- The US blocks imports of milk, fresh fruits, and vegetables from the four areas worst affected.
Day 14 - Thursday, March 24
- Tokyo tap water is again within acceptable drinking limits for infants, after briefly testing too radioactive.
- Three Fukushima workers report exposure to radiation.
Day 15 - Friday, March 25
- Chief Cabinet Secretary Yukio Edano said Friday that residents living between 20 and 30 km from the Fukushima nuclear power plant are being urged to “voluntarily evacuate.” Residents in those areas had been previously told to stay indoors.
- Edano stressed that current radiation levels in the area do not necessitate immediate evacuation.
- Workers began pumping fresh water into the Unit 1 and Unit 3.
- White smoke continues to be seen coming from the Unit 2 and Unit 4 reactors.
Day 16 - Saturday, March 26
- Levels of radioactive iodine reached 1,250 times above normal in seawater off the coast of Japan's stricken Fukushima Daiichi nuclear plant, raising concerns about a containment crack.
- Fresh water is being pumped in to cool reactors 1,2, and 3.
- Electricity has been restored to the control room of Unit 2.
Day 17 - Sunday, March 27
- Radioactive iodine higher than the acceptable limit for infants has been found in tap water in Saitama, Ibaraki, Tochigi, and Chiba Prefectures.
- Authorities of Tochigi Prefecture as well as the cities of Hitachi and Kasama in Ibaraki Prefecture have advised not to give tap water to babies.
- Workers evacuated from the Fukushima complex after radiation readings outside Unit 2 were reported to spike to 10 million times normal levels.
- TEPCO apologized for mistake in readings, which they said were 100,000 times higher than normal, not 10 million times normal levels.
Day 18 - Monday, March 28
- A lack of fuel, coordination, and logistical issues are still the biggest challenges facing Japan’s emergency relief efforts.
- Officials are working to contain high levels of Radioactive water detected at the No. 2 reactor underground tunnels and basement.
- Small amounts of plutonium have been discovered outside Fukushima's reactor buildings. The radioactive material was found in five separate soil samples. External exposure poses little health risk, according to the US Environmental Protection Agency.
Day 19 - Tuesday, March 29
- Focus remains on Unit 2, where workers are attempting to contain a possible water leak.
- Officials say plutonium found in the soil near the plant could mean the reactors experienced a partial meltdown.
Day 20 - Wednesday, March 30
- Tepco announces it will decommission four of the six nuclear reactors at Fukushima Daiichi
- Radioactive water in and around reactor buildings is delaying cooling efforts.
- Japan's nuclear safety agency says the radioactive iodine at 3,355 times the legal limit does not pose a health threat.
Day 22, Friday, April 1
- Researchers say that the tsunami reached as high as 29.6 meters in Ofunato City, Iwate. It was previously thought the highest wave reached only to 20 meters.
- The Nuclear safety agency says radioactive material 4,385 times the legal limit has been found in sea water near the plant.
Day 23, Saturday, April 2
Day 24, Sunday, April 3
- Tepco begins dumping radioactive water from the Fukushima site into the sea in order to make it easier to cool the plants.
Day 25, Monday, April 4
- Tepco said some 11,500 tons of contaminated water would be released today in order to make room for more radioactive water storage.
- Authorities say they have still not found the source of a leak they believe is responsible for highly contaminated water levels near Fukushima.
Day 26, Tuesday, April 5
- Tepco is pumping millions of gallons of radioactive water into the sea.
- Levels of radioactive contamination in fish are exceeding health guidelines for the first time.
- Tepco says it has slowed the flow of contaminated water leaking into the sea from the No. 2 reactor.
Day 27, Wednesday, April 6
- Officials say they have stopped the leaking radioactive water, measured at 7.5 million times the legal limit, from reactor No. 2 into the ocean.
- Tepco is now concerned about a build-up of hydrogen inside reactor No. 1, which may the reactor's core could be damaged.
- Japan's official spokesperson, Yukio Edano apologized to neighboring countries for not notifying them before they started pumping low-level radioactive water this weekend into the ocean.
Day 28, Thursday, April 7
- A 7.4 aftershock hits Japan's northeast coast near Sendai at 11:32 p.m. local time.
- Tepco temporarily evacuates Fukushima
- Power is disrupted at Onagawa nuclear power plant, 75 miles northeast of Fukushima.
Some key numbers as of Friday, April 1:
- Death toll: 11,600
- Unaccounted for: at least 16,450
- Displaced: about 500,000
- Buildings damaged or destroyed: more than 155,000
- International Search and Rescue specialists on the ground according to OCHA: 543 (14 teams) from 12 countries.
- Countries that have pledged assistance to Japan: more than 130
- Estimated damage cost: $309 billion