1.1 Case studies

Question 1

Indian Ocean Tsunami 2004 - description

Answer 1

• 26th December 2004
• hypocentre 160km away from Sumatra, Indonesia
• first waves arrived 20mins after quake
• 800km/h waves

Question 2

Indian Ocean Tsunami 2004 - causes

Answer 2

under sea 9.2 magnitude earthquake caused by subduction of Indian plate under Burma plate

Question 3

Indian Ocean Tsunami 2004 - Social Impacts

Answer 3

• No tsunami warning system in place
• 300,000 deaths
• 1.7 million left homeless
• Wide spread of disease (cholera and dysentery) through mixing sea water with sewage
• 6 million people requiring emergency aid

Question 4

Indian Ocean Tsunami 2004 - economic impacts

Answer 4

• loss of earnings from tourism
• fishing industry damaged through destruction of ports, boats, equipment
• destruction of crops and farmland by seawater
• transport links damaged

Question 5

Indian Ocean Tsunami 2004 - environmental impacts

Answer 5

• mangrove forests damaged
• 8 million litres of oil leaked from oil plants in Indonesia
• coral reefs damaged/destroyed

Question 6

describe the Nepal Earthquake

Answer 6

• 25 April 2015
• 7.9 on Richter scale
• depth of 8.2km
• Destructive plate margin
• Indo-Australian plate colliding with Eurasian Plate
• interplate

Question 7

Nepal Earthquake - secondary impacts

Answer 7

• Landslides and avalanches which blocked roads and hampered relief efforts
• Avalanche on Mt Everest killed 19 people
• Avalanche in the Langtang reagion left 250 missing
• Landslide blocked River Kaii Gandaki - which caused flooding in capital
• 9000 deaths
• 22,000 injuries
• $10bn in damages

Question 8

describe the Gujurat earthquake

Answer 8

• 2001
• intraplate
• 7.7 magnitude
• in northern India
• along a rift fault associated with India + Eurasian plate boundary

Question 9

Impacts of Gujurat earthquake

Answer 9

• 13-20,000 deaths
• 167,000 injured
• 340,000 buildings destroyed

Question 10

Eyjafjallajokull 2010 - description

Answer 10

• stratovolcano - explosive eruptions associated with the mid-atlantic ridge
• prior to eruption, 5000 smaller earthquakes recorded near to the volcano’s crater, located beneath a glacier
• 14th April 2010, erupted from main crater in rthe middle of the glacier

Question 11

Primary impacts of Eyjafjallajokull eruption

Answer 11

• 150m ice cap melted causing flooding
• 800 people evacuated
• 20 farms destroyed
• schools and businesses closed
• damage to crops and livestock

Question 12

Secondary impacts of Eyjafjallajokull eruption

Answer 12

• jokulhaup flooding damaged homes
• costs of repairing flood defences
• long-term increased tourism and businesses - 1.7million tourists came as a result
• Roads bulldozed to allow flood water to reach sea
• European travel industry had £1.7bn losses
• 6 flightless days
• London lost £102mn of tourist income

Question 13

Describe the Mt. St. Helens eruption.

Answer 13

• located in Washington state
• deadliest volcanic event in US history
• along subduction zone of Juan de Fuca and North American plates
• plinian eruption
• VEI = 5
• volcano continuously active until 2008

Question 14

Mt. St. Helens’ 1980 eruption
- What were the precursor events leading up to the eruption that alerted geologists?

Answer 14

• small earthquakes in March 1980
• frequency of high magnitude earthquakes increased to about 8 per day
• phreatic eruptions (steam eruptions)
• formation of new crater at summit of volcano
• surface deformation due to accumulation of magma at shallow depths

Question 15

Mt. St. Helens’ 1980 eruption
- What caused the May 18th lateral blast?

Answer 15

• 5.1 magnitude earthquake directly beneath volcano and northern slope collapsed, causing large debris avalanche
• sudden pressure change led to expansion of volcanic gases in the underlying magma
• culminated in a northward-directed lateral blast

Question 16

Mt. St. Helens 1980 eruption - secondary impacts

Answer 16

• 600km^2 of surrounding forest destroyed
• 57 deaths
• 200 homes destroyed
• volcanic ash deposited across Washington, Idaho, and Montana

Question 17

Mt. St. Helens 1980 eruption - how has the eruption changed volcanic monitoring in the area?

Answer 17

• network of seismometers and GPS stations set up
• data collected during and after eruption provided a baseline for other studies
• enabled scientists to observe reawakening of a volcano with modern monitoring techniques

Question 18

Describe the 2022 Tonga earthquake

Answer 18

• occurred on uninhabited island within Tongan archipelago in south pacific
• part of volcanic arc along subduction zone extending from New Zealand to Fiji
• most powerful point of eruption occurred on Jan 15, sending an ash plume over 20km into the atmosphere
• VEI = 4
• 0.5km^3 released

Question 19

Impacts of the 2022 Tonga earthquake

Answer 19

• caused tsunami waves reaching as far as Japan (at least 3 people killed in Peru)
• Tonga is a developing nation (104th on 2020 HDI ranking)
• estimated US$90m in damages (18.5% of Tonga’s GDP)
• damaged 600 buildings
• crops lost, fisheries damaged
• internet coverage not restored until 5 weeks after eruption

Question 20

Describe the Pacific Tsunami Warning System

Answer 20

• 46 member states
• over 90% of tsunami casualties occur in area
• aims to increase community resilience
• uses seismic data from IRIS
• uses DART system - ocean bottom pressure recorders that measure changes in sea surface height

Question 21

Advantages of Pacific Tsunami Warning System

Answer 21

• Advanced warning saves lives
• identify long-term patterns and areas at risk
• centralised data is available for researchers and aid providers

Question 22

Disadvantages of Pacific Tsunami Warning System

Answer 22

• not much notice
• expensive so out of reach for LICs
• require mobile devices

Question 23

Describe the Haiti earthquake

Answer 23

• 2010
• magnitude 7
• conservative plate boundary between North American and Caribbean plates
• shallow focus: 5 miles deep

Question 24

Impacts of Haiti Earthquake 2010 (5)

Answer 24

• 316,000 deaths
• 280,000 buildings destroyed
• 1.3 million left homeless
• hospitals and schools damaged
• airport control tower destroyed, preventing aid from landing

Question 25

Long-term impacts of Haiti earthquake

Answer 25

- only 48% of $13.34bn donations reached Haiti as a lot of money west to NGOs not in Haiti so overheads had to be paid - cholera outbreak caused by waste from UN peacekeeper base leaking into local river caused 10,000 deaths - many still homeless, access to services is poor - by 2013, 279,000 people lived in 'tent cities'

Question 26

Haiti earthquake - why were the impacts so severe?

Answer 26

- no building regulations so buildings were poor quality and unable to withstand earthquake - part of presidential palace collapsed, trapping government officials inside and leading to delays in organising relief efforts - morgues quickly overwhelmed so bodies buried in mass graves or left in the open - language barriers, purchase of overpriced supplies, and staffing changes meant NGOs were slow to provide housing

Question 27

Describe the 2011 Tohoku Earthquake

Answer 27

- 9.0 magnitude - epicentre 43 miles east of Tohoku, Japan - 20mile deep focus - destructive plate margin: subduction of pacific plate under Eurasian plate - friction build-up led to 'megathrust' quake

Question 28

Tohoku Earthquake - short-term impacts

Answer 28

- over 20,000 deaths - 332,395 buildings destroyed, leaving 130,927 homeless - 800 aftershocks - tsunami reaching 40m high, completely overtopping existing 12m-high tsunami defences that cost billions to build - despite tsunami warning system, only 58% of coastal residents responded to warnings and headed to higher ground - total energy released was 600m times that of Hiroshima bomb and shifter Earth's axis

Question 29

Tohoku Earthquake - Long-term impacts

Answer 29

- tsunami flooded nuclear power stations and led to meltdown of 7 reactors, including Fukushima - economic costs of $235bn, most expensive disaster in history - Three reactors overheated, melted and released radioactivity into the air during explosions, and also into groundwater which eventually reached the Pacific Ocean