Japanese earthquake (Tohuku)

why did the earthquake occur

there is a destructive plate margin

the pacific plate moves 9cm per year towards the Okhotsk plate and is subducted at the Japan trench

the eurasian, philippine and pacific plates converge here

part of the ring of fire

around 1,500 earthquakes annually which are strong enough to be felt

when did the earthquake occur

11th march 2011

what magnitude was the earthquake

9.0

what was the 11th of march earthquake equivalent to

600 hiroshima atomic bombs

what caused the tsunami

the epicenter was located under the ocean floor, and so all the water above it was pushed upwards and displaced

water surged away in all directions at a speed of 800km/hr

it took 10 minutes to reach the coast of japan

the offshore area is particularly shallow and so the friction between the moving water and the seabed slows the lower part of the wave.
The rest of the water was held back and so the tsunami grew in height

how tall was the tsunami

up to 40m in some areas

how far inland did water flow

10km

what was a further issue caused by the tsunami within minutes

Sendai airport was rendered unusable, limiting accessibility of aid

what were primary impacts

building collapse and buildings set alight due to gas and petrol sites

tsunami flooded an area of 500km squared and caused devistation to everything in its path

in Ichihara near tokyo an oil refinery was engulfed in flames as fuel tanks exploded

in Minami- Sanriku half the population of 17,000 died

over 18,000 were dead or missing

what made some of the primary impacts less severe

in Tokyo skyscrapers shook but earthquake proof design limited damage

the tsunami warning system saved many lives

what were the secondary effects

half a million homeless

150,000 in temporary shelters for weeks

1 million homes without running water and 6 million without electricity

shortages of food, water, petrol, and medical supplies

nuclear incidents

what were the nuclear incidents

explosions and radiation leaks at the Fukushima Daiichi nuclear power plant days after the earthquake

power supply and cooling system were severed by the earthquake

tsunami destroyed back up generators

what were the effects of the fukushima nuclear incident

5 years after the explosions 100,000 residents had not returned home (half a million were evacuated)

adverse health impacts- physical and psychological

no deaths attributed to ionizing radiations

cost estimated at 200-300 bn usd direct and to Japans economy

contaminated water had to be cleaned- high radiation levels found as far as tokyo

what other hazards does japan experience

typhoons

volcanic eruptions

typhoons in japan example

typhoon hagibis oct 4-20th 2019

claimed 23 lived

caused severe flooding in tokyo and coastal areas

wind speeds of 225km/hr- worst in 60 yrs

7 million urged to leave homes

the Japanese meteorological agency monitors events and gives emergency warnings for wind, rain, and flooding

volcanic activity in Japan example

Mount Unzen dormant for 200 yrs but entered active phase with earthquakes, steam, and ash eruptions

lava dome appeared may 1991 producing pyroclastic flows

evacuation order from government and defined as restricted zone 12,000 evacuated in June with increasing intensity

march 1992 saw 500 pyroclastic flows which destroyed buildings

eruption calmed in 1995

civilian deaths prevented but 43 died from media and science

what is the risk of disaster affected by

the intersection between the hazard and vulnerability of people

examples of natural hazard impacts on risk

past recurrence intervals

future probability

magnitude

spatial extent

examples of vulnerable system/ people

exposure, sensitivity and resilience of:

population

economy

land use and development

cultural assets

natural resources

ability resoucres/ willingness to:

mitigate

prepare

respond

recover

what impacted the risk in japan

it was a large event and a variety of natural hazards due to the location in the tycoon paths and at the boundary of several plates

what lessened the risks

Japan is well developed with hazard management systems and mitigation strategies

what were the social impacts of the earthquake/ tsunami

20,000 deaths

4 entire commuter trains carrying 100 passengers were lost

prolonged problems for all affected areas, 6 million without power lines and 1 million without safe drinking water

350,000 sheltering in public buildings and evacuation centers

half a million made homeless

freezing temps (night temps of -4) hit survivors as a cold front fell over northern japan and dampness made the cold worse

in one residential home alone 11 elderly people died due to the cold within a few days

what were the environmental consequences

Tokyo sky scrapers swayed and an oil refinery nearby was engulfed in flames as oil tanks exploded

500km squared flooded

towns and cities along the 1,300 mile coastline were submurged or wiped out by waves

5 million tonnes of debris washed out into the ocean adding tonnes of plastic to the great pacific garbage patch

what were the economic consequences

future risks from a population imbalance- falling birth rates and shortage of workers

but a first rank global power and G7 nation

2019 GNI 41,690 per capita, similar to UK but falling- now 37,000

total damages estimated at $300 bn- most costly natural disaster in history

supply chains disrupted due to value in manufacturing and car industry

toyota nissan and sony suspended production due to damage to manufacturing

stock market crashed on fears of nuclear incident

japan relies on nuclear for 45% of energy production

what was a consequence that went against japanese culture

people were scavenging in the streets to find food and looted shops

this went against japanese pride and the importance of reputation

what are the future challenges

UN estimates Japan could reach a crisis point by 2050 when the economically active population is outnumbered by the economically inactive population

the dependency ratio will be above 1

what is resilience

the sustained ability of a community to utilise available resources to respond to, withstand and recover from the impacts of natural disasters

how is Japan resilient to natural disasters

a diligent and disciplined population and sophisticated culturally and economically- well placed to recover from a natural disaster

all school children practice earthquake drills monthly

fire departments take groups to earthquake simulators

September 1st disaster prevention day

high GDP allows investment in repairs and adaptation

what is a limitation of resilience

the scale of the disaster was so great that the population was less able to cope

densely populated so a large number of people are affected

lack of agricultural land reduces ability to cope

aging population may decrease resilience

what is adaptation

people see they can prepare for and therefore survive the events through prediction and preparation

what shows japans adaptation

immediately after the earthquake all radio and TV switch immediately to official earthquake coverage, informing public of risks including tsunamis

phone alerts via nowcasting

high capacity to cope eg 40% of japans coastline has a sea wall to withstand tsunami waves

string of buoys in the pacific ocean to detect the tsunami and alert islands

rapid mobilisation of emergency services-100,000 soldiers, helicopters etc

iodine tablets distributed near fukishima

what is mitigation

interventions designed to reduce, prevent, or minimise the long term adverse impacts of environmental hazards, climate change, or natural disasters

examples of mitigation in Japan

skyscrapers in Tokyo were earthquake resistant to avoid collapse ad well as other buildings- high regulations

Japanese meterological agency is set up for the prediction of earthquakes and tsunamis. Detected earthquake and issued warnings just after P waves, before the more damaging S waves

prediction of the tsunami gave people 20 minutes to get to safety

tsunami walls are 10m high around over 40% of the coastline

plans of $6.8 bn to link 440 sections of wall together to create 400km wall over 12m tall in some areas