2.1 Earthquakes Flashcards
Boxing Day Tsunami
- Magnitude 9 off Sumatra Indonesia - 4h largest Earthquake
- Burma Tectonic plate override India tectonic plate
- Generated tsunami causing 283,100 people, 14,100 still missing and 1.1m displaced in 11 countries
- 12m waves swept 2km onshore
Banda Aceh worst hit area - poor and low lying close to epicentre
Haiti
- 7 magnitude 25km SW of capital Port au Prince, 13km low - shallow
- 5.9 magnitude aftershocks
- 300,000 died 1m displaced
- Strike slip fault where North American and Caribbean plates collide
- Hospitals and government buildings destroyed
- Power water, infrastructure, food looting and riots, poor sanitations, cholera outbreaks
- incoming aid delayed as airport destroyed
- Many lived in poor shacks - no building regulations and cheap buildings
- Most of city built on loose sediment led to liquefaction
- Highly populated and high density
- No army or help
- Poor recovery - 280,000 still lived in camps, lacked all necessities
- Cost up to $9bn
Causes of Tohuku and Fukushima EQ
Magnitude 9.0 earthquake 32km off East Japan - Pacific plate subduct Eurasian plate
- Uplift of 35m, affected 2000km of the coast
- Defences inadequate - wave nearly 38m high hit settlement of Miyagi
- Jagged coast funnelled water into bays
- Most land in low lying areas
- Soft reclaimed land increased damaged
- Wave 10m high up to 38m
- Tsunami warning 3 mins after EQ, 20m later
Impacts of fukushima
- Caused fires in oil refinery, millions without power, Fukushima nuclear power station damaged - radioactive leaks
- Tsunami of 4.1m and 7.3m also occurred
- Tsunami inundated 561km2
- 23,000 died, 5000 injured, 130000 displaced
- 1.3m buildings damaged, 300k destroyed
- Dams, bridges and railways destroyed
- Cost over $300bn
- Infrastructure destroyed - many in temporary housing
- Landslides and liquefaction contributed
- 25m tonnes of wreckage
- Reconstruction agency cost $300bn a year
- People rather live on coasts due to opportunity so hard to manage
What was the management of the Tohuku EQ?
- Dense seismometers failed as only coped up to 8 magnitude
- Tsunami walls 8m high, Fukushima 5-7m high
- Planned out drills and hazard maps to households
- Schools got to high ground
- Reconstructed high ground
- Reconstruction agency made
- 300k put in temporary housing
- £25bn in resettlement
- Sky villages made - elevated islands of residence
- Closed 50 nuclear power plants
Nyiragongo
- Can be very destructive if at high speeds and combine with volcanic gas release
- Moved at 40pkh
- 242 died from CO2 asphyxiation
- 15% of Goma destroyed
- 60m high projection
- observatory funded - scientists study volcano at the peak
- volcanic gases and acid rain caused damage
- 3m of lava covered parts of the city
Ashfall
Eyjafjallajokull
- 10km ash plume
- Volcano on ice cap, made more explosive
- Mix of water and lava funnelled ash upwards
- 100,000 flights cancelled
- loss of $2.6bn
- Reduced visibility
- Killed lifestock and land
Ash
Mount Ontake
- 57 died from inhalation of ash
- Phreatic eruption
- Destroyed homes and ski resorts
- Killed 150
Pyroclastic flows
Mount Unzen
- 12k evacuated
- Pyroclastic flow from collapsing lava dome
- Travelled 4.5km when lava dome collapsed triggering pyroclastic flow
- Killed 43 scientists in volcano observatory
- Generated at least 10,000 small pyroclastic flows, 2,000 houses
- Lahars frequent by heavy rains since
- Managed with construction of dikes in river valleys
Nuees ardentes
Mt Pelee
-Magma dome collapsed, magma erupted out creating nuee ardente - swept 6km downslope and killed 28,000
Ways of monitoring
- 14 seismographs on Montserrat
- 5 Tilt meters on Montserrat
- InSAR satelittes
- Radon gas used at St Helens
- 42 Evacuation plans for eruptions
- Kilauea eruption diverted
- Sprayed used at Mount Etna
Goma
Observatory:
-Measures invisible odourless CO2 seeping through cracks, forming deadly pools and seeps around cracks
Photography:
-IR cameras connected to computer every 10s. Pressure in magma chamber affected lava valve above - variation in level of 40 expects eruption
Sulphur dioxide - rise signals lava moving up, measure ppm of gas, gases unreliable as may be other factor
Drone - thermal camera - shows warm sub surface to see where weakest areas are and where new vents could form
-Drones lose connection quickly when exposed to heat
- Searching for lava bombs, silica levels, white crystals
- Microphones used to pick up infrasound
Lava lake temperatures, chemical composition of rocks and lava
-Increased warning time up to 3 weeks
-Erupted in 2021 killing 32 and 1000 houses - many did not evacuate despite warning
LA EOC
- 40 suspension points making it floating
- Roll side to side, bouncing building up and down as it rolled
- Ground around shakes, building appears still
- Pipies and comms designed with slack so don’t snap
Transamerica building
- 49 stories
- 212 ft spine flanked by structures
- Truss system provides vertical and horizontal support
- Large horizontal bare shear forces
- Horizontal X bracing resists movement about vertical axis
- Reinforced with steel
- Quake wrap fibre cloth strengthens beams - cost effective
- Emergency gas shut off valves
Education and prediction in US
Red cross Tsunami:
-Go as high and far, emergency preparedness list evacuation plan - protect family, pets and home
- FEMA playbook - increases preparedness and resilience for disasters, maintains or quickly reastablish business, increased knowledge, builds morale and trust - involves disaster kits with basic essentials
- National Shaekout day with drills on how to be safer - drop and cover - encourages to update emergency plans
- Tsunami awareness day - raise risk education, what to do
Myshake app - damage and shaking reports by community members and global authority information
-Citizens informed of shaking or seismic activity
-Pacific tsunami warning centre - 15 active 24/7 - 4 levels watch, advisory, warning and information statement
