Key Takeaways
- The 2011 Tōhoku earthquake had a moment magnitude of 9.0 to 9.1, making it the most powerful earthquake ever recorded by instrumental means and the fourth largest since 1900.
- The earthquake's epicenter was located approximately 70 kilometers east of the Oshika Peninsula of Tōhoku, with coordinates 38.322°N 142.369°E.
- The rupture along the subduction zone lasted approximately 3 minutes, with seismic waves propagating at varying speeds.
- Over 15,000 deaths confirmed, with 2,527 missing as of 2023.
- Iwate Prefecture reported 4,673 deaths and 774 missing.
- Miyagi Prefecture had 9,548 deaths, the highest toll.
- Maximum tsunami height recorded at Miyako was 40.5 meters.
- Run-up height at Aneyoshi reached 37.1 meters above sea level.
- Tsunami waves arrived at Sendai coast 28 minutes after earthquake.
- Estimated direct economic loss from earthquake and tsunami was ¥16.9 trillion (US$210 billion).
- Over 123,000 houses completely destroyed.
- 29,500 km of roads damaged, costing ¥1.2 trillion to repair.
- Unit 1 at Fukushima Daiichi had core meltdown starting 5 hours after quake.
- Hydrogen explosion in Unit 1 reactor building on March 12, 2011.
- Total radioactive release estimated at 520,000 TBq iodine-131 equivalent.
The 2011 Japan earthquake triggered a massive tsunami that caused widespread destruction and a nuclear crisis.
Casualties and Human Impact
- Over 15,000 deaths confirmed, with 2,527 missing as of 2023.
- Iwate Prefecture reported 4,673 deaths and 774 missing.
- Miyagi Prefecture had 9,548 deaths, the highest toll.
- Fukushima Prefecture recorded 1,615 deaths and 2,247 missing.
- Approximately 90% of deaths were due to drowning in the tsunami.
- 6,157 injuries reported across affected prefectures.
- Over 162,000 people were evacuated from Fukushima due to radiation fears.
- Elderly over 60 accounted for 65.4% of fatalities.
- Children under 15 made up only 2.8% of deaths.
- 47,600 residential buildings completely destroyed.
- Mental health issues affected 20% of survivors one year later.
- Over 400,000 evacuees in temporary housing by end of 2011.
- Suicide rates in affected areas rose by 10% post-disaster.
- Foreign nationals deaths totaled 14, including 10 Chinese.
- Rikuzentakata city lost 1,749 residents, 10% of population.
- Over 1 million people received health checkups in relief efforts.
- PTSD prevalence was 15.1% among Miyagi survivors.
Casualties and Human Impact Interpretation
Earthquake Magnitude and Seismology
- The 2011 Tōhoku earthquake had a moment magnitude of 9.0 to 9.1, making it the most powerful earthquake ever recorded by instrumental means and the fourth largest since 1900.
- The earthquake's epicenter was located approximately 70 kilometers east of the Oshika Peninsula of Tōhoku, with coordinates 38.322°N 142.369°E.
- The rupture along the subduction zone lasted approximately 3 minutes, with seismic waves propagating at varying speeds.
- Peak ground acceleration reached 2.7g at the K-NET Iwate station, the highest ever recorded worldwide.
- The earthquake triggered over 1,000 aftershocks greater than magnitude 4.0 within the first month.
- Seismic energy released was equivalent to 475 megatons of TNT, about 8,000 times the Hiroshima atomic bomb.
- The fault slip was up to 50 meters along a 200 km by 500 km fault area.
- P-wave arrival time at Tokyo was 00:46:50 JST on March 11, 2011.
- The earthquake caused a static displacement of up to 5.3 meters horizontally and 3.3 meters vertically at GPS stations.
- Focal depth was estimated at 24 to 30 km beneath the Pacific Ocean floor.
- The mainshock was followed by a magnitude 7.9 aftershock 29 minutes later.
- Broadband seismic records showed rupture propagation velocity of 2.0-2.5 km/s.
- The earthquake shifted Japan's main island by 2.4 meters eastward.
- Over 4,000 foreshocks and aftershocks were recorded in the year following the event.
- The moment tensor solution indicated a thrust fault mechanism on the Pacific Plate subduction.
- Ground shaking intensity reached JMA scale 7 in Kurihara, Miyagi Prefecture.
- The earthquake's duration was over 6 minutes as felt in Tokyo.
- Tsunami earthquake component contributed to underestimated initial magnitude.
- Harvard CMT magnitude was revised from 9.0 to 9.1.
- The event ruptured multiple segments of the Japan Trench.
Earthquake Magnitude and Seismology Interpretation
Economic and Infrastructure Damage
- Estimated direct economic loss from earthquake and tsunami was ¥16.9 trillion (US$210 billion).
- Over 123,000 houses completely destroyed.
- 29,500 km of roads damaged, costing ¥1.2 trillion to repair.
- 2,126 road bridges collapsed or severely damaged.
- 4,062 km of railway lines disrupted.
- Sendai Airport runway submerged under 5m tsunami water.
- 232 residents' lives lost in Okushiri fishing port alone.
- Industrial production dropped 40% in March 2011 due to power shortages.
- 11,000 ha of farmland inundated by saltwater.
- Cost to rebuild ports and harbors was ¥1.4 trillion.
- 47 dams failed or damaged, affecting water supply.
- GDP impact was -0.5% in Q1 2011.
- 3.6 million tons of debris generated, cleanup cost ¥2.3 trillion.
- 1,044 schools damaged, 211 completely destroyed.
- Healthcare facilities damage cost ¥200 billion.
- 2.5 million households without electricity immediately after.
- Insurance payouts totaled ¥1.1 trillion.
- Reconstruction budget allocated ¥19 trillion over 10 years.
- Over 300 hospitals damaged or destroyed.
- Fishing industry losses reached ¥100 billion.
Economic and Infrastructure Damage Interpretation
Fukushima Nuclear Incident
- Unit 1 at Fukushima Daiichi had core meltdown starting 5 hours after quake.
- Hydrogen explosion in Unit 1 reactor building on March 12, 2011.
- Total radioactive release estimated at 520,000 TBq iodine-131 equivalent.
- Unit 2 containment failed on March 15 due to pressure suppression.
- Over 160,000 residents evacuated from 20 km exclusion zone.
- Peak radiation dose rate at plant gate was 101 mSv/h on March 15.
- 3.4 million becquerels per m² cesium-137 deposited in Fukushima.
- Cooling systems failed due to loss of AC power at 15:37 JST.
- Unit 4 spent fuel pool fire occurred on March 15.
- Decontamination efforts covered 23,000 hectares by 2014.
- TEPCO admitted groundwater contamination with 240 trillion Bq tritium.
- IAEA rated accident as INES Level 7.
- 110,000 tons of contaminated water stored as of 2013.
- Robot surveys found fuel debris in Unit 2 pedestal.
- Annual radiation exposure limit set at 1 mSv for residents.
- 44,000 households in difficult-to-return zone as of 2021.
- Decommissioning cost estimated at ¥22 trillion by 2060.
- Seawater release of treated water began August 2023 with 1.3 million tons planned.
- Thyroid cancer cases in screening rose to 266 by 2020.
- Fuel removal from Unit 3 completed in 2021, 566 assemblies.
- Over 900 fuel assemblies removed from Unit 4 pool by 2014.
Fukushima Nuclear Incident Interpretation
Tsunami Characteristics
- Maximum tsunami height recorded at Miyako was 40.5 meters.
- Run-up height at Aneyoshi reached 37.1 meters above sea level.
- Tsunami waves arrived at Sendai coast 28 minutes after earthquake.
- Maximum inundation depth in Kesennuma was 10 meters.
- Tsunami traveled 10 km inland in Sendai plain.
- Over 80% of tsunami deaths occurred within 3 km of coast.
- Tsunami flow speeds exceeded 10 m/s in many bays.
- The tsunami generated mega-boulders weighing up to 100 tons.
- Far-field tsunami reached Hawaii with waves up to 2.7 meters.
- Tsunami warning issued for Pacific rim countries within 3 minutes.
- Inundation area totaled 561 km² across Iwate, Miyagi, Fukushima.
- Tsunami height at Ofunato port was 40.1 meters.
- Second tsunami wave was larger than first in many locations.
- Tsunami deposited sediments up to 5 meters thick.
- Waves propagated across Pacific at 700 km/h speed.
- Over 11,000 fishing boats destroyed by tsunami.
- Tsunami eroded coastline by up to 500 meters in places.
- Maximum tsunami amplitude offshore was 3.2 meters.
- The maximum tsunami run-up height in Japan was 40.5 m at Miyako.
Tsunami Characteristics Interpretation
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