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 homesand 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.
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, says the international alert should be from a level 4 disaster to a level 6 incident.
Foreign companies begin to order evacuations of their employees.
Some key numbers as of Tuesday, March 15:
- Death toll: 2,722
- Confirmed missing: 3,742
- Evacuated: 439,337 (from 10 prefectures)
- Houses damaged: 68,231
- Houses destroyed: 4,648
- Countries offering aid: 102