Henry Lansdell - 3706
Earthquake Case Study; Honshu, Japan
On the 11th of March 2011 at precisely 14:46, a
catastrophic earthquake hit Japan, with the hypocentre
(focus of oceanic earthquake) approximately 100km east
of Honshu in the Pacific Ocean. The oceanic eruption was
the largest Japan had ever seen and globally the 5th; being
of magnitude 9.0 with an extensive duration of 6 minutes,
with the earthquakes shallow focus of 32km it was
evident that destruction was to be inflicted. Geological
reasoning for the mass earthquake was due to the build
up of pressure and friction that was ultimately released
from the subduction of the Pacific plate underneath the
Eurasian (destructive plate margin) at a rate of
approximately 8-9cm/year. The earthquake triggered
hundreds of aftershocks and are still occurring today, this
contributed towards damage upon Japan, with the largest
proceeding at 7.4Mw, down towards 4.5Mw. As the
country is notorious for experiencing many earthquakes,
Japan’s infrastructure is built in a seismic-resistant
manner which moves with the shockwaves to absorb
some of the energy emitted from earthquakes. This
therefore reduced damage heavily.
As this was an oceanic earthquake, the release of a 5-8 metres upthrust influenced a catastrophic
tsunami, in which headed towards Japan’s 1,360km coastline (primarily north eastern) and was
imminent to cause damage. It was estimated that this wave was 38.9 metres in height, largely due
the topography of the region; the shallow coastline enabled the water to build up into a larger, and
more threatening wave. This tsunami was rated as a “major tsunami” by the Japan Meteorological
Agency and was predicted the most serious on their warning scale. On this basis, the tsunami only
took approximately 10 minutes to reach the first area affected (Kamaishi and Ofunato), leaving little
time for evacuation for those situated there. Furthermore, the intensity of the earthquake was so
great that evacuations had to be made within the Western hemisphere, as the primary shockwaves
emitted travel through the mantle, outer and inner core. The Pacific Tsunami Warning Centre
announced warnings that were given in Hawaii, Caribbean for precaution measures, this illustrates
how large the earthquake and hazards associated were.
Primary Effects
Primary effects refer to the impacts caused directly from the earthquake itself, rather than factors
that operate in a chain (secondary) reaction from the earthquake. Having such a high intensity, it is
unsurprising that there were some colossal associated primary effects, both due to physical and
human factors.
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The death toll was confirmed at 15,854, with the tsunami accounting for 80% of deaths, it is
clear that the associated hazards of the initial earthquake impacted the most. This was largely
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due to drowning and the destruction of infrastructure that was forced to collapse on inhabitants,
it was also estimated that 60% of the deaths were over that of age 60. Furthermore, the
mountainous topography of Japan means that limited land can be built upon, therefore resulting
in denser populations and significantly more deaths.
Corresponding to the deaths, 125,000 buildings were damaged or destroyed in response to the
tsunami channelling through the streets, including many important transport services. This
would leave millions of people homeless without commodities such as essential shelter, food
and water, deteriorating the quality of life.
The tsunami completely flooded around 200 miles2 of land across the eastern coast of Japan,
destroying approximately 58,000 acres of valuable farmland by saltwater inundation (mostly rice
paddies); this means that the land cannot be cultivated for 2+ years, therefore causing damage
to the economic climate of Japan.
Liquefaction occurred in regions with loose to medium density saturated sand and silts (such as
Urayasu city) and covered an extensive area of over 150km from the fault rupture. Though
generally the engineering efforts in improving the ground of areas was effective, it was shown in
regions that it poses threat to damaging the structures from the ground movement and lateral
spreading, this was clear with some of the roads in Tokyo. Liquefaction makes the ground prone
to cracking and therefore possible collapse – a significant potential hazard for both humans and
infrastructure if land was to completely avalanche.
In result of the great tsunami, the emergency generators required to cool the Fukushima nuclear
reactors were disabled (with visual explosions). This was ultimately due to the sheer height of
the wave; subsequent waves reaching 14 metres consequently overwhelmed the wall that could
only withstand 5.7 metres. This lead to the emitting of radioactive substances (40,000 times the
usual level), which was potentially dangerous to those inhabitants surrounding the area,
therefore additional people were evacuated from the region to avoid respiratory and poisoning
issues.
Contributing to the death and destruction of infrastructure, the tsunami burst gas pipes in which
caused the ignition of flames with fire activity. These household fires were generated due to
general activity and that the gas and oil pipes were not generally well protected/insulated, a
clear flaw within the utility structure.
With further reference to fire, the oil refinery in Ichihara was engulfed in an inferno due in
reaction to the earthquake, influencing economic, social and environmental negative factors.
Carbon dioxide emissions contributed greatly to the pollution and enhance the greenhouse
effect, whilst posing a threat to those living within the region with respiratory issues.
Additionally, millions of homes were left without any electricity due to the immediate closure of
11 nuclear reactors and 21 thermal units across Japan, enclosing for approximately 9% of Japans
capacity greatly affected operating within Japan which heavily rely on computers within the 21st
century.
The 10 metre high sea wall defence at Taro, Miyako, was breached by the tsunami in which was
designed to restrict access of the water gushing onto the streets. However this specific event
exceeded this height due to its sheer intensity corresponding to the land subducting at the sea
wall (lowering by approximately 1 metre) which reduced its height and effectiveness. Though it
somewhat mitigated the force and velocity of the water flooding onto the streets, it was
insufficient in completely eliminating the damage.
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The tsunami even reached highland regions approximately 6 miles from the coast near Sendai,
this was largely due to both the tsunami severity and valley channelling, in which built up the
surface area of the water to reach these regions. This influenced environmental effects, evident
with the flooding and creation of a lake.
Secondary Effects
Secondary effects refer to the impacts that are created in reflection to the primary impacts
themselves. With Japan having such great primary impacts, it’s to be expected that the country had
have expansive secondary effects in which affect its economic, environmental and social wellbeing.
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Economical prospects of Japan were greatly affected as £150 billion was estimated to be lost
(the most expensive natural disaster on record) from the damage/collapsing of infrastructure,
including the incineration of the mass amount of crude oil. This means that this money will need
to be spent on repair, which could consequently take a long time to revitalise Japan to its
former, prosperous self. Residents were forced to live in economically deprived conditions in
response to the destruction of homes and loss of businesses and jobs, reducing the economic
contribution to the country.
The heavy damage to roads, railways and other infrastructure resulted in the severe disruption
to the public transport network, leaving the sector unusable in some locations such as the
Tohoku Expressway. Railway services were suspended until almost 2 weeks after the initial
eruption and tsunami, leaving an estimated 20,000 individuals left stranded at major stations in
Tokyo alone. In addition, this negatively effects the economy of the area, as the
Due to the time of eruption (14:46), 100,000 children were uprooted from their homes, with
many being separated from their families. The time of day meant that the children were at
school (away from parents/guardians) and could not reunite amongst all of the havoc. This
resulted in 82+ children being orphaned, and will negatively impact these individuals lives being
separated from their biological family.
In total 1800 homes were washed away as the Fujinima irrigation dam was ruptured from both
the combination of the high intensity earthquake and the associated catastrophic tsunami, this
therefore contributed to the amount of deaths and buildings damage and destroyed. This
supports the statement that the earthquake’s intensity was completely unexpected, thus
meaning Japan’s previous preparation/prevention systems were rendered ineffective.
Whether it be coincidental or otherwise a geological relationship, the Shinmoedake volcano (950
miles from the earthquake epicentre) in on the south island of Kyushu was thought to be
“reactivated” after a dormancy period of 52 years with an eruption on the 13th March (2 days
after the Tohoku earthquake). The composite volcano forced hundreds of people to evacuate
the area as it was spewing hot ash and boulders, forming an ash plume spreading over a 2 mile
area. As Japan had already experienced devastating effects of the initial earthquake, this
contributed to further disturbance of the country by closing additional airlines and other various
transport services.
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Management and Response
With such catastrophic effects, response and management was imminent in order to retain previous
levels of economical, environmental and social status. Japan being a HIC meant it is was able to fund
itself greatly (though with external help) to restore these levels however the time period in which
would be extensive, meaning that Japanese lives would still be in detriment.
Immediate Response
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Japan was generally well prepared for the earthquake and tsunami as it has all of the seismic and
hydrological technology to measure intensity from previous ruptures and tsunamis (being near
four plate boundaries this is unsurprising). Warnings then proceeded from the warning system,
resulting in public announcement through text messages, news alerts and police alerting
residents. This therefore gave a margin of time for evacuation to mitigate the impact, however
the public became desensitised by many false alarms and placed sheer reliance on the seismic
resistant infrastructure (such as the sea walls) in which was proven ineffective.
The initial response of the earthquake news was lacking urgency as the country experiences
earthquakes on a frequent basis, and therefore was expected to be a regular, ineffective
rupture. This disbelief meant that people did not evacuate the area immediately, therefore
being a prime reason for the high death toll.
Emergency relief was sent out from across the globe from a variety of NGOs (such as the
Japanese Red Cross reporting $1 billion in donations) providing supplies of water, food, shelter
and medical aid due to now having a fuel shortage and bad weather conditions. This significantly
contributed to the reduction of decease from homeless survivors and risk of associated diseases,
such as cholera outbreaks.
The Japanese government mobilised the self-defence forces corresponding to the help of
external countries to search and rescue any survivors that lay within the amount of rubble from
the destroyed buildings. This would ultimately reduce the death toll for those still buried
amongst the amount of destruction; though still a huge challenge due to the large amount of
buildings destroyed.
Immediately after the earthquake alert, worldwide media publications (specifically television) in
order to make both tourists and citizens of Japan aware of the potential danger and encourage
evacuation to mitigate impacts. NHK had been noted for its calmness in contrast to foreign news
programmes such as Fox News Channel and CNN (American); however the American broadcasts
did provide incorrect factual information. Critics also noticed that the Japanese news media had
been overly cautious at times in order to reduce panic; this could also be due to expecting a
calmer earthquake that normally occurs and therefore underestimating the power of this one.
Long Term Response
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The Government also responded to this disaster by reviewing their methods on predicting
earthquakes and tsunamis as well as cutting short the time between the disaster and the
response by improving communications and Sirens.
In March, Japan’s Meteorological agency issued an earthquake warning, followed by a Tsunami
warning. This meant that many people were able to escape to higher ground, but the short time
(20 minutes), meant that thousands could not escape and resulted in unfortunate deaths.
The billions of dollars invested within earthquake resilience technology proved affective against
the severe earthquake. However against the associated hydrological effects (tsunami,
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liquefaction etc), it proved ineffective in response to a variety of human and physical factors
(primarily physical) previously explained.
The Fukushima power plant is to be moved further inland in order to avoid damage and
therefore lower the chances of further radiation being emitted into the earth’s atmosphere.
Though it can be argued if this relocation will ultimately reduce the chance of this damage, as
Japan experiences frequent earthquakes, and the tsunami was shown to reach even the
highlands of Japan.
Human and Physical Factors Influence Severity
It has previously been highlighted that a number of human and physical factors affected the high
degree of impact the earthquake and tsunami had upon Japan. The table below highlights these
factors and gives reasoning as to how it has influenced the level of impact in terms of loss of life and
structural damage across Japan.
Human Factors
Due to the topography (mainly mountainous),
much of Japan is uninhabitable, resulting in a
high population density in many of the
floodplains of Japan on the eastern coast. This
therefore increased the probability of decease as
there are more people situated nearer the
epicentre of the earthquake.
Furthermore, the earthquakes was
underestimated as Japan regularly experiences
earthquakes of lower frequencies and therefore
lead to the disbelief and lack of urgency to
evacuate – therefore contributing to the high
death toll. This was despite having extensive
earthquake duration of 5 minutes, irregular in
terms of the normal length of time earthquakes
occur for in Japan.
The height of defence at Fukushima nuclear
power plant (5.7m) was insufficient in stopping
water from interfering with the reactor,
therefore influencing the mass explosion, and
hydrogen radiation emitted into the
atmosphere, both polluting the atmosphere and
posing a threat to human respiration.
Gas and oil pipes were not insulated well enough
in order to withstand the power of the tsunami
and therefore generated an inferno, adding to
both further destruction of infrastructure and
loss of life.
The tsunami channelling between the buildings
consequently increased the height of the waves
as it builds up, therefore increasing the amount
of damage inflicted upon buildings and higher
risk for loss of life.
Physical Factors
The intensity of the earthquake (magnitude 9.0)
was 4 times greater than Japan had experienced
before (8.6 Mw). On this basis, the energy
emitted from the shockwaves were a lot larger
than expected and contributed heavily to the
degree of destruction due to more shaking.
The earthquake happened to occur at an oceanic
margin (convergence of Pacific plate and
Eurasian plate), and at great intensity to cause a
catastrophic tsunami; formed from the release
of the Pacific plate’s pressure. This associated
hydrological hazard accounted for 80% of the
deaths within Japan, showing that the physical
factors had a clear influence on the degree of
severity.
Japan’s east coast has a shallow sea floor in
which influenced the size and increased the
concentration of the tsunami wave; it meant
that the tsunami could build up to an estimated
height of 38.9 metres resulting in a more
aggressive impact as the wall would destroy
buildings.
Within the more alpine environments of Japan,
the water had the ability to channel through the
highland valleys, therefore building up in height
as it squeezes through. This would lead to
additional environmental flooding and erosion as
well as the disturbance/destruction of more
rural locations.
Additionally, the land at the 10 metre sea wall
subducted by approximately 1 metre out of
human control by lowering the height of the
wall, rendering it ineffective against the sheer
height of the tsunami. Though it did mititgate
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some of the velocity and force it was travelling
at, it still seeped into Taro, Miyako, destroying
infrastructure and taking lives in its path.
Overall, it is clear that the degree of impact on Japan as a country is based primarily on physical
factors rather than the human factors. With reference to the table above, it is clear that Japan is
generally well prepared for earthquakes (walls and seismic-resistant building structures) designed to
mitigate impacts; however the sheer intensity of the initial earthquake (9.0Mw) and associated
tsunami was shown to breach these attempts through geological impacts such as land subduction
and liquefaction. It is therefore clear that determined that the high death toll and sheer damage of
infrastructure meant was ultimately due to physical factors, however a lack of urgency despite
warning is also used to support this theory.