Japan Tsunami was the most powerful known earthquake to have hit Japan, and one of the five most powerful earthquakes in the world overall since modern record-keeping began in 1900. The tsunami caused a number of nuclear accidents, primarily the ongoing level 7 meltdowns at three reactors in the Fukushima I Nuclear Power Plant complex, and the associated evacuation zones affecting hundreds of thousands of residents.

The earthquake triggered extremely destructive tsunami waves of up to 40.5 metres (133 ft) in Miyako, Iwate, Tohoku. The earthquake triggered powerful tsunami waves that reached heights of up to 40.5 metres (133 ft) in Miyako in Tohoku's Iwate Prefecture, and which, in the Sendai area, travelled up to 10 km (6 mi) inland. The earthquake moved Honshu 2.4 m (8 ft) east and shifted the Earth on its axis by estimates of between 10 cm (4 in) and 25 cm (10 in).

The Tsunami caused a number of nuclear accidents, primarily the ongoing level 7 meltdowns at three reactors in the Fukushima I Nuclear Power Plant complex. The Japanese National Police Agency confirmed 15,844 deaths, 5,890 injured, and 3,451 people missing across eighteen prefectures, as well as over 125,000 buildings damaged or destroyed.

The earthquake and tsunami caused extensive and severe structural damage in Japan. The earthquake and tsunami caused extensive and severe structural damage in Japan, including heavy damage to roads and railways as well as fires in many areas, and a dam collapse. Japanese Prime Minister Naoto Kan said, "In the 65 years after the end of World War II, this is the toughest and the most difficult crisis for Japan.

Heavy damage to roads and railways as well as fires in many areas, and a dam collapse. The total energy released, also known as the seismic moment (M0), was more than 200,000 times the surface energy and was calculated by the USGS at 3.9×1022 joules, slightly less than the 2004 Indian Ocean quake. This is equivalent to 9,320 gigatons of TNT, or approximately 600 million times the energy of the Hiroshima bomb.

Houses are swept by a tsunami in Natori City. Japan's National Research Institute for Earth Science and Disaster Prevention (NIED) calculated a peak ground acceleration of 2.99 g (29.33 m/s²) The largest individual recording in Japan was 2.7g, in the Miyagi Prefecture, 75 km from the epicentre; the highest reading in the Tokyo metropolitan area was 0.16g.

A tsunami carries buildings across waters in Kamaishi city port. Japan experienced over 900 aftershocks since the earthquake, with about 60 registering over magnitude 6.0 Mw and at least three over 7.0 Mw. Four days later on 11 April, another strong magnitude 6.6 Mw aftershock struck Fukushima, causing additional damage and killing a total of three people.

Ships and boats are washed ashore in Hachinohe, Aomori Prefectur, Japan. In the Philippines, waves up to 0.5 m (1.6 ft) high hit the eastern seaboard of the country. Some houses along the coast in Jayapura, Indonesia were destroyed. Authorities in Wewak, East Sepik, Papua New Guinea evacuated 100 patients from the city's Boram Hospital before it was hit by the waves, causing an estimated US$4 million in damages.

Houses, cars and debris are swept towards a highway. In the Galapagos Islands, 260 families received assistance following a 3 m (9.8 ft) surge which arrived 20 hours after the earthquake, after the tsunami warning had been lifted.[145][146] There was a great deal of damage to buildings on the islands and one man was injured but there were no reported fatalities.

Houses are swept by a tsunami. All of Japan's ports were briefly closed after the earthquake, though the ones in Tokyo and southwards soon re-opened. Fifteen ports were located in the disaster zone. The north-eastern ports of Hachinohe, Sendai, Ishinomaki and Onahama were destroyed, while the Port of Chiba (which serves the hydrocarbon industry) and Japan's ninth-largest container port at Kashima were also affected though less severely.

A collapsed building. Japan's transport network suffered severe disruptions. Many sections of Tōhoku Expressway serving northern Japan were damaged. The expressway did not reopen to general public use until 24 March 2011. All railway services were suspended in Tokyo, with an estimated 20,000 people stranded at major stations across the city. In the hours after the earthquake, some train services were resumed.

A damaged Building. Cellular and landline phone service suffered major disruptions in the affected area. On the day of the quake, American broadcaster NPR was unable to reach anyone in Sendai with working phone or Internet. Internet services were largely unaffected in areas where basic infrastructure remained, despite the earthquake having damaged portions of several undersea cable systems landing in the affected regions; these systems were able to reroute around affected segments onto redundant links.

A damaged building. The aftermath of the earthquake and tsunami included both a humanitarian crisis and a major economic impact. The tsunami resulted in over 300,000 displaced people in the Tōhoku region, and shortages of food, water, shelter, medicine and fuel for survivors. The economic impact included both immediate problems, with industrial production suspended in many factories, and the longer term issue of the cost of rebuilding.