Earthquake and Tsunami Details
– Magnitude 9.1 earthquake occurred on March 11, 2011, at 14:46 JST
– Epicenter approximately 72km east of the Oshika Peninsula of Tōhoku, Japan
– Lasted approximately six minutes
– Tsunami triggered by the earthquake
– Tsunami waves reached heights of up to 40.5 meters in Miyako, Tōhoku
– Waves traveled at a speed of 700km/h and reached up to 10km inland in the Sendai area
– Residents of Sendai had only eight to ten minutes of warning
– More than a hundred evacuation sites were washed away
– Official figures released in 2021 reported 19,759 deaths, 6,242 injured, and 2,553 people missing
– 228,863 people were still living away from their homes in temporary housing or due to permanent relocation in 2015
– The tsunami caused the Fukushima Daiichi nuclear disaster
– Insured losses from the earthquake alone were estimated at US$14.5 to $34.6 billion
– The World Bank estimated the economic cost at US$235 billion, making it the costliest natural disaster in history
– Over eight hundred aftershocks of magnitude 4.5 or greater have occurred since the initial quake
– Aftershocks follow Omori’s law and could continue for years
– The earthquake moved Honshu 2.4m east and shifted the Earth on its axis by estimates of between 10cm and 25cm
– The earthquake occurred where the Pacific Plate is subducting under the plate beneath northern Honshu
– The rupture length of this magnitude earthquake is usually at least 500km
– The hypocentral region of this earthquake extended from offshore Iwate Prefecture to offshore Ibaraki Prefecture
– Other major earthquakes with tsunamis struck the Sanriku Coast region in 1896 and 1933
Energy and Intensity
– Surface energy of seismic waves: 1.9×10 joules
– Seismic energy could power a city the size of Los Angeles for a year
– Seismic moment: 3.9×10 joules
– Peak ground acceleration: 2.99 (29.33m/s^2)
– Largest recording in Japan: 2.7 in Miyagi Prefecture
– Seismic intensity scale: Maximum of 7 in Kurihara, Miyagi Prefecture
– Other prefectures recorded an upper 6 on the scale
– Areas closest to the epicenter experienced the largest shifts
– Coastline dropped vertically by 0.6 meters, allowing the tsunami to travel farther and faster
– Earth’s axis shifted by estimates of 10cm to 25cm
– Over 1,000 aftershocks experienced in Japan
– Several aftershocks registered over magnitude 6.0 and 7.0
– Major aftershock on April 7 with a magnitude of 7.1
– Additional aftershock on April 11 in Fukushima, causing damage and fatalities
– Aftershocks continued for several years, with over 800 aftershocks of magnitude 5.0 or greater
Impact on Communities and Recovery Efforts
– The city of Rikuzentakata, Iwate Prefecture, suffered extensive damage
– Entire towns were destroyed in tsunami-hit areas, including Minamisanriku
– The high death toll was due to the unexpectedly large water surge and inadequate sea walls
– The tsunami also destroyed or heavily damaged cities such as Kamaishi, Miyako, Ōtsuchi, and Yamada
– The most severe effects of the tsunami were felt along a 670-kilometer stretch of coastline
– Significant erosion and land subsidence reported in affected areas
– Delayed evacuations were caused by factors such as underestimation of tsunami height and power failures
– The Rikuzen-Takata coastline has not naturally recovered at a desirable rate since the tsunami
– 58% of people in coastal areas heeded tsunami warnings and headed for higher ground
– The Japanese government study found that of those who attempted to evacuate after hearing the warning, only 5% were caught in the tsunami
Tsunami Observations and Warning System
– Tsunami maximum readings of over 3 meters were recorded at various locations along the coastline of Japan
– The earliest recorded tsunami maximum readings ranged from 15:12 to 15:21, between 26 and 35 minutes after the earthquake
– Many areas were also affected by waves of 1 to 3 meters in height
– The Japan Meteorological Agency warned that tsunamis may be higher than those observed at the observation sites
– The tsunami warning system was updated in 2013 to address shortcomings, including the use of new teleseismometers and GPS tidal meters
– The updated system provides words describing the emergency situation instead of quantitative predictions for powerful earthquakes
Tsunami Impact in the Pacific and Shortcomings in the Warning System
– The tsunami propagated throughout the Pacific Ocean region, reaching the entire Pacific coast of North and South America
– Warnings were issued and evacuations were carried out in many countries bordering the Pacific
– The tsunami warning issued by the Japan Meteorological Agency was rated as a major tsunami
– The actual height prediction varied, with the greatest being 6 meters for Miyagi
– The tsunami inundated a total area of approximately 561 square kilometers in Japan
– Observed data from tidal meters and wave meters were not fully reflected in the warning system, causing some residents to underestimate the danger
– The bulletin included initial tsunami observation details and more detailed information about the tsunami’s impact Source: https://en.wikipedia.org/wiki/2011_T%C5%8Dhoku_earthquake_and_tsunami
On 11 March 2011, at 14:46 JST (05:46 UTC), a Mw 9.0–9.1 undersea megathrust earthquake occurred in the Pacific Ocean, 72 km (45 mi) east of the Oshika Peninsula of the Tōhoku region. It lasted approximately six minutes, causing a tsunami. It is sometimes known in Japan as the "Great East Japan Earthquake" (東日本大震災, Higashi nihon daishinsai), among other names. The disaster is often referred to by its numerical date, 3.11 (read san ten ichi-ichi in Japanese).
| 東北地方太平洋沖地震 東日本大震災 | |
 A helicopter flies over the port of Sendai to deliver food to survivors of the earthquake and tsunami. | |
 | |
   Tokyo Sendai | |
| UTC time | 2011-03-11 05:46:24 |
|---|---|
| ISC event | 16461282 |
| USGS-ANSS | ComCat |
| Local date | 11 March 2011 |
| Local time | 14:46:24 JST |
| Duration | 6 minutes |
| Magnitude | 9.0–9.1 Mw |
| Depth | 29 km (18 mi) |
| Epicenter | 38°19′19″N 142°22′08″E / 38.322°N 142.369°E |
| Type | Megathrust |
| Areas affected |
|
| Total damage | $360 billion USD |
| Max. intensity | |
| Peak acceleration | 2.99 g |
| Peak velocity | 117.41 cm/s |
| Tsunami | Up to 40.5 m (133 ft) in Miyako, Iwate, Tōhoku |
| Landslides | Yes |
| Foreshocks | List of foreshocks and aftershocks of the 2011 Tōhoku earthquake |
| Aftershocks | 13,386 (as of 6 March 2018[update]) |
| Casualties |
|
| Citations | |
It was the most powerful earthquake ever recorded in Japan, and the fourth most powerful earthquake recorded in the world since modern seismography began in 1900. The earthquake triggered powerful tsunami waves that may have reached heights of up to 40.5 meters (133 ft) in Miyako in Tōhoku's Iwate Prefecture, and which, in the Sendai area, traveled at 700 km/h (435 mph) and up to 10 km (6 mi) inland. Residents of Sendai had only eight to ten minutes of warning, and more than a hundred evacuation sites were washed away. The snowfall which accompanied the tsunami and the freezing temperature hindered rescue works greatly; for instance, Ishinomaki, the city with most deaths, was 0 °C (32 °F) as the tsunami hit. The official figures released in 2021 reported 19,759 deaths, 6,242 injured, and 2,553 people missing, and a report from 2015 indicated 228,863 people were still living away from their home in either temporary housing or due to permanent relocation.
The tsunami caused the Fukushima Daiichi nuclear disaster, primarily the meltdowns of three of its reactors, the discharge of radioactive water in Fukushima and the associated evacuation zones affecting hundreds of thousands of residents. Many electrical generators ran out of fuel. The loss of electrical power halted cooling systems, causing heat to build up. The heat build-up caused the generation of hydrogen gas. Without ventilation, gas accumulated within the upper refueling hall and eventually exploded causing the refueling hall's blast panels to be forcefully ejected from the structure. Residents within a 20 km (12 mi) radius of the Fukushima Daiichi Nuclear Power Plant and a 10 km (6.2 mi) radius of the Fukushima Daini Nuclear Power Plant were evacuated.
Early estimates placed insured losses from the earthquake alone at US$14.5 to $34.6 billion. The Bank of Japan offered ¥15 trillion (US$183 billion) to the banking system on 14 March 2011 in an effort to normalize market conditions. The World Bank's estimated economic cost was US$235 billion, making it the costliest natural disaster in history. According to a 2020 study, "the earthquake and its aftermaths resulted in a 0.47 percentage point decline in Japan's real GDP growth in the year following the disaster."
