Geophysical hazards
Case studies
Earthquakes
Haiti Earthquake (2010)
Hazard profile:
Magnitude: 7.0
25km away from port au prince whose population was about 3 million
13 km below surface
Frequency: 3.0-3.9 almost daily, stronger ones not as frequent
Duration: main earthquake 30-40 seconds, aftershocks occurred in the following days, around 12 days, 52 aftershocks
Aftershocks as strong as 5.9, 9 km below surface, 56 km south from city
Areal extent spatial concentration (size of area covered by the hazard)
Epicenter in town of Leogane, slightly west of Haiti’s capital. Extreme to strong shaking occurred in radius of 80(ish) km from epicenter. Shocks were felt throughout Haiti and Dominican republic as well as in parts of Cuba, Jamaica and Puerto Rico.
Speed of onset: no warning signal, suddenly, no forshock, no instrument to forecast
Regularity: happens relatively frequently but random
Deaths: up to 300000, injured: 250000, homeless: over 1 million
Context + vulnerability:
City buildings are mainly shanties and badly constructed house
Overcrowded
tin -roofed shacks, unstable slopes
3 million people needed emergency help, only 200000 received food from UN
One of the poorest (80% live in poverty) → no insurance, leftover money, living situation, no money to support local community
Vulnerable, only two fire stations
Country had no army that could have come in to help
Local time: 16:53 , late afternoon, population spread out in risky areas, workplace, home, transportation
Plates: enriquillo-plantain-garden fault
Impact:
Environmental:
deforestation and clearance for temporary camps
Small scale pollution due to leak of oil and chemicals into surrounding area
Pollution of water supply leading to cholera epidemic
Social
3 million people affected
up to 300000 deaths,
injured: 250000,
homeless: over 1 million
Economic impacts:
Commercial buildings broke down
Business destroyed, rebuilding required a lot of money which the country didn’t have
Damage to clothing industry
Airport and port damaged impacting imports and exports as well as slowdown in rescue operations
Political impact
Appeal for aid to other countries
Haiti's justice system remains in disarray
Overall:
Food:
Disruption of agriculture
Food aid dependency
Increase in food prices
Malnutrition
Water:
Destruction of infrastructure
Reliance on contaminated water
Cholera outbreak
Shelter
Widespread homelessness
Heath and medical surfaces
Collapsed system
trauma
The christchurch, New Zealand, (2010-2012) Earthquake
Hazard profile:
Magnitude: 7.1, aftershocks up to 6.3
Frequency: 150-200 earthquakes that are strong enough to be felt every year
Duration: 10s, aftershocks continued until 2012
Areal extent spatial concentration
Speed of onset: very short/half a year
Regularity random
Deaths: 1 casualty at main earthquake, around 180 at 6.3 aftershock (2011)
Context 2010:
Population of christchurch: 386000
Occurred at 4,35am on a saturday morning
Reasons for lack of casualties: high building standards, time of occurence
Impact 2010
Sewers were damaged
Water pipes broken and water supply damaged
Power disrupted up to 75%
Airport closed and flights canceled
Context 2011
Magnitude 6.3
Occurred at 12:51pm (lunch) on tuesday
Epicenter closer to christchurch
Earthquake was shallower
Building weakened by 2010 earthquake
Impact 2011
Killed 185 people
Liquefaction , caused more than 400000 tonnes of silt
Volcanoes
Nyiragongo, DR. Congo, 2021 eruption
Hazard profile:
Magnitude:
Frequency (how often does it occur): on average every 20 years
Duration (length of time the environmental hazard exists): Lasted around 6h, but seismic activity continued in the following 10 days
Areal extent spatial concentration (size of area covered by the hazard): Lava flow stopped short of Goma city’s limits (2M people) 20km to south of volcano, destroying several villages and killing 32 people.
Speed of onset (time difference between start and peak of event)
Regularity (is it regular or random)
Context:
Occurred on plate boundary, part of east african rift valley
Goma city’s limits (2M people) 10km to south of volcano
Nyiragongo is a steep sided, active volcano
Different events like 2002, which killed 250 people
2021 occurred in similar pattern to 2002
Lava lake in crater, in both eruptions, fissures opened on the (south) side of the volcano and streams of lava from the lake drained through
Lava reached 64 km/h, was flowing towards Goma and border with rwanda
2021 occurred on saturday evening (7pm) (we will focus on it)
Volcanic explosivity index 1 (low), but volume and speed of lava flowing was fast
Return interval around 20 years, 1977, 2002, 2021
Main eruption lasted only a few hours, but lava flow and secondary impacts such as ground deformation, gas emissions, aftershocks, persisted for weeks
Lava cover approximately over 13 square kilometers
Onset of eruption rapid, little warning
Due to speed and no warning, people had minimal time to evacuate
Eruptions happen random
Secondary hazards:
Gas emissions, co2 and sulfur
Seismic activity
Lake kivu explosion risk: fears of limnic eruption (gases are trapped at the bottom of the lake and then erupt) lake kivu contains a lot of co2 and methane
Nyiragongo has the largest and most active lava lake in the world
Effects:
primary
At least 32 people died
450000 people displaced
Around 17 villages were badly affected, destroying homes, schools and hospitals
Secondary
Earthquakes destroyed and damaged buildings
Magma full of co2, collects in low areas due to density, can be toxic for humans to breath
3000-8000 went to rwanda with hope to find safety
10 people died in road accidents during evacuation, 4 prisoners died when trying to escape
Economic:
Destruction of infrastructure
Aid needed for recovery costs
Closure of businesses, destruction of agricultural land
Political:
Unsatisfaction with government
Cross border relations with up to 8000 people finding refuge in rwanda, increased tensions
Environmental:
Destruction of vegetaion and land
Gas emissions causing for ex. Acid rain
Mt Helen, USA, 1980 eruption
Hazard profile:
Magnitude, caused by an earthquake of magnitude 5, energy released equals 26 megatons of tnt
Frequency, active phases and dormancy, in last 500 years there were 4 major eruptions, but also many smaller ones
Duration, the eruption lasted for nine hours, but activity was already visible 2 months before and the ash impacted the region for a longer period of time afterwards
Areal extent spatial concentration, lahars reached the cowlitz river, about 80km away, caused complete darkness 400 km away, ash fell visibly 1500 km away, ash surrounded earth in 15 days
Speed of onset, first signs of volcanic activity started 2 months before, but the final build up and explosion happened fast caused by a bigger earthquake
Regularity, happens in phases but pretty random
La Palma, Spain, 2021 eruption
Part of canary islands
Canary islands have over 30 volcanos, 10 of them on la palma
On african plate, occurs on a hotspot
Hot spot: columns of superheated magma causes earth's crust to melt and make it thinner
Warning was sent out, nearly 7000 were evacuated
Earthquake swarm took place, more than 20000 earthquakes took place in days and weeks before earthquake
Primary impacts:
7000 people had to leave their homes
1300 homes were destroyed
Churches, schools etc destroyed
Secondary:
Hundreds acres of farmland, including banana plantations, destroyed
Flights cancelled
Island size increased du to magma flowing into the ocean
Responses:
Repair to damage was promised
Cost of damage
Landslides
Sri Lanka, 2016
Tropical storm caused severe floods and landslides.
Hazard profile:
Magnitude: Over 58,000 houses were damaged, 93 people killed and almost half a million people affected.
Frequency (how often does it occur): About 50 landslides annually. The months of May, June and November to December have many more recorded landslides, correlating with the 2 monsoon seasons.
Duration (length of time the environmental hazard exists): Rain-induced rapid long-traveling landslides (RRLL), so they are fast moving and difficult to anticipate. Floods lasted from 13-19 May in 2016.
Areal extent spatial concentration (size of area covered by the hazard): Landslide and slope cut failure warnings were issues for Badulla, Bandarawela, Ella, Haliela, Hadummulla, Haputale, Lunugala, Passara, Uva-Paranagama and Welimada.
Speed of onset (time difference between start and peak of event): Typically rainfall triggers landslides within hours or days depending on the intensity of the rain, the saturation of the soil, etc. Don’t know for 2016 landslide in particular.
Regularity (is it regular or random): Every year during monsoon seasons.
Kalimpong, India (Urban)
in kalimpong, west bengal, india, overlooking the river teesta, overlooked by summit of khangchendzonga, dumsi pakha i a low wealth area, with a lot of small houses located on the side of a steed hill
Two main elements causing the landslides: 1. Poor water management, water from kalimpong is discharged without any control into gullies that run through dumsi pakha, towards end of dry season, the channel is dried out and full of garbage, additionally there is an extensive instability of the flanks of the channel, when they fall into the channel they block it briefly and then cause a destructive debris flow
2. Slope disruption, some problems are more local, houses are build on small terraces that are created by caring a port of the slope, behind these buildings the slope is now even steeper and more susceptible to landslides
Magnitude, usually small, but sometimes more significant
Frequency, usually occurring when heavy rain, more smaller ones
Duration, for years already
Areal extent spatial concentration, affecting mainly dumsi pakha, but also whole kalimpong
Speed of onset, very fast, almost no preparation time, although warned by heavier rainfall
Regularity, monsoon season