Term Paper
Japan Earthquake and Tsunami
Brittany Sosa
Report
The magnitude-9.0 earthquake struck Japan at 2:46 pm. (The early estimate of magnitude
8.9 was later revised upward.) The epicenter was located some 80 miles (130 km) east of the city
of Sendai, Miyagi prefecture, and the focus occurred at a depth of 18.6 miles (about 30 km)
below the floor of the western Pacific Ocean. The earthquake was caused by the rupture of a
stretch of the subduction zone associated with the Japan Trench, which separates the Eurasian
Plate from the sub-ducting Pacific Plate. A part of the subduction zone measuring approximately
190 miles (300 km) long by 95 miles (150 km) wide lurched as much as 164 feet (50 m) to the
east-southeast and thrust upward about 33 feet (10 m). The March 11 temblor was felt as far
away as Russia, Taiwan, and China. It was preceded by several foreshocks, including a
magnitude-7.2 event centered approximately 25 miles (40 km) away from the epicenter of the
main quake. (Library, 2013)
The sudden horizontal and vertical thrusting of the Pacific Plate, which has been slowly
advancing under the Eurasian Plate near Japan, displaced the water above and started a series of
highly destructive tsunami waves. A wave measuring some 33 feet high inundated the coast and
flooded parts of the city of Sendai, including its airport and the surrounding countryside.
According to some reports, one wave penetrated some 6 miles (10 km) inland after causing the
Natori River to overflow. Damaging tsunami waves struck the coasts of Iwate prefecture
extending along the Pacific coast south of Miyagi. As the floodwaters retreated back to the sea,
they carried with them enormous quantities of debris, as well as thousands of victims caught in
the deluge. Large stretches of land were left submerged under seawater, particularly in lowerlying areas. The earthquake triggered tsunami warnings throughout the Pacific basin. The
tsunami raced outward from the epicenter at speeds that approached about 500 miles (800 km)
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Term Paper
Japan Earthquake and Tsunami
Brittany Sosa
per hour. It generated waves 11 to 12 feet (3.3 to 3.6 m) high along the coast
of Kauai and Hawaii in the Hawaiian Islands chain and 5-foot (1.5-metre) waves along the island
of Shemya in the Aleutian Islands chain. Several hours later 9-foot (2.7-metre) tsunami waves
struck the coasts of California and Oregon in North America. Finally, some 18 hours after the
quake, waves roughly 1 foot (0.3 m) high reached the coast of Antarctica and caused a portion of
the Sulzberger Ice Shelf to break off its outer edge. (Oskin, 2013)
Ultimately, the official total for the number of those confirmed dead or listed as missing
from the disaster was about 18,500, although other estimates gave a final toll of at least 20,000.
Of those, fewer than 100 were from prefectures other than Iwate, Miyagi, and Fukushima.
Miyagi prefecture suffered the greatest losses, with some 10,800 killed or missing and another
4,100 injured. The great majority of those killed overall were drowning victims of the tsunami
waves. Although nearly all of the deaths and much of the destruction was caused by the tsunami
waves along Japan’s Pacific coastline, the earthquake was responsible for considerable damage
over a wide area. (Oskin, 2013)
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Term Paper
Japan Earthquake and Tsunami
Brittany Sosa
Analysis
This event could not have been forecasted. “Two days prior to the massive temblor, a
magnitude-7.2 earthquake with three aftershocks greater than magnitude 6.0 hit offshore eastern
Honshu. These quakes caused little damage even though the main rupture was only 8 kilometers
deep. It also produced a maximum 60-centimeter-high tsunami, which struck the coast half an
hour after the quake. This fooled everyone. Given the earthquake’s large magnitude and the
smaller aftershocks that occurred as expected over the next day, no one thought that these could
be foreshocks of an even larger event. But it now looks like those quakes were all foreshocks for
the magnitude-9.0 quake that hit two days later, just 40 kilometers north of the magnitude-7.2
event.” (Sorkhabi, 2011) The earthquake triggered tsunami warnings throughout the Pacific
basin, and Japan sent out warnings “Residents of Tokyo received a minute of warning before the
strong shaking hit the city, thanks to Japan's earthquake early warning system. The country's
stringent seismic building codes and early warning system prevented many deaths from the
earthquake, by stopping high-speed trains and factory assembly lines. People in Japan also
received texted alerts of the earthquake warning on their cellphones.” (Oskin, 2013)
“It is important to collect and analyze as much data as possible about past and present
earthquakes. Some of Japan’s other largest quakes that have hit off Honshu and produced
tsunamis include an estimated magnitude 8.6 in July A.D. 869, an estimated magnitude 8.5 in
June 1896, a magnitude 8.4 in March 1933 and a magnitude 7.4 in June 1978. The risk of the Big
One hitting the populous Kanto region, where Tokyo is located, is far from over. Recent fault
stress modeling by Ross Stein of the U.S. Geological Survey in Menlo Park, Calif., and Shinji
Toda of Kyoto University in Japan suggests that after the March 11 mega quake, the crustal
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Term Paper
Japan Earthquake and Tsunami
Brittany Sosa
stress off Honshu may have transferred to adjacent segments along the subduction zone and
loaded the existing faults in the upper plate with increased stress.” (Sorkhabi, 2011)
Following the earthquake and tsunami fires in several cities broke out, including a
petrochemical plant in Sendai. Thousands of homes were completely or partially destroyed by
the temblor and aftershocks. Infrastructure also was heavily affected throughout eastern Tohoku,
as roads and rail lines were damaged, electric power was knocked out, and water and sewerage
systems were disrupted. In Fukushima a dam burst close to the prefectural capital, Fukushima
city. Hundreds of aftershocks, dozens of magnitude 6.0 or greater and two of magnitude 7.0 or
greater, followed in the days and weeks after the main quake. Nearly two years later, on
December 7, 2012, a magnitude-7.3 tremor originated from the same plate boundary region. The
quake caused no injuries and little damage. (Library, 2013)
This was a disaster because the affect it had on the people living in Japan knowing the
probability of natural disasters and building nuclear power plants near a subduction zone on the
pacific coast. “The reactors at the three nuclear power plants closest to the quake’s epicenter
were shut down automatically following the temblor, which also cut the main power to those
plants and their cooling systems. However, inundation by the tsunami waves damaged the
backup generators at some of those plants, most notably at the Fukushima Daiichi plant, situated
along the Pacific coast in northeastern Fukushima prefecture about 60 miles (100 km) south of
Sendai. With power gone, the cooling systems failed in three reactors within the first few days of
the disaster, and their cores subsequently overheated, leading to partial meltdowns of the fuel
rods. Melted material fell to the bottom of the containment vessels in reactors 1 and 2 and burned
sizable holes through the floor of each vessel, which partially exposed the nuclear material in the
cores. Explosions resulting from the buildup of pressurized hydrogen gas in the outer
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Term Paper
Japan Earthquake and Tsunami
Brittany Sosa
containment buildings enclosing reactors 1, 2, and 3, led to the release of significant levels of
radiation from the facility in the days and weeks following the earthquake. Japanese officials
established an 18-mile (30-km) no-fly zone around the facility, and an area of 12.5 miles (20 km)
around the plant was evacuated. The appearance of increased levels of radiation in some local
food and water supplies prompted officials in Japan and overseas to issue warnings about their
consumption. At the end of March, seawater near the Daiichi facility was discovered to have
been contaminated with high levels of radioactive iodine-131. (Shah, 2011)
The great majority of Japan remains unaffected. The tsunami damaged the built
environment and natural environment along the shorelines of northern Honshu, Japan’s biggest
island. The same region was the area most damaged by the earthquake, the consequences of
which are most felt in the built environment – buildings, roads, rail lines and pipelines, etc. There
are not any real natural benefits from this natural disaster, but it has been a lesson to the rest of
the world about the danger of nuclear power plants in regions prone to natural disasters. In Japan,
residents are still recovering from the disaster. Radioactive water was recently discovered
leaking from the Fukushima Daiichi Nuclear Power Plant. Japan relies on nuclear power, and
many of the country's nuclear reactors remain closed because of stricter seismic safety standards
since the earthquake. Two years after the quake, about 300,000 people who lost their homes were
still living in temporary housing. (Oskin, 2013)
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Term Paper
Japan Earthquake and Tsunami
Brittany Sosa
Works Cited
Library, C. (2013, September 20). CNN. Retrieved from Japan Earthquake - Tsunami Fast Facts:
http://www.cnn.com/2013/07/17/world/asia/japan-earthquake---tsunami-fast-facts/
Oskin, B. (2013, August). Live science. Retrieved from Japan Earthquake & Tsunami of 2011: Facts and
Information: http://www.livescience.com/39110-japan-2011-earthquake-tsunami-facts.html
Shah, A. (2011, April 6). Global Issues. Retrieved from Japan Earthquake, Tsunami and Nuclear Crisis:
http://www.globalissues.org/article/794/japan-earthquake-tsunami-nuclear
Sorkhabi, R. (2011, May). Earth magazine. Retrieved from Earth the science behind the headlines:
http://www.earthmagazine.org/article/japans-megaquake-and-killer-tsunami-how-did-happen
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