PMT - hazards caused by seismic events Flashcards
what are some of the hazards that can be caused by seismic hazards?
shockwaves
aftershocks
tsunamis
liquefaction
landslides and avalanches
what is shockwaves (seismic waves)?
two plates move side by side and friction builds up
pressure increases and is stored as potential energy and builds up
the pressure becomes too much and its transferred into kinetic energy which is released and vibrates throughout the ground
how does a tsunami form?
an oceanic crust is jolted during an earthquake and the water above the plate is displaced
water travels fast with a low amplitude
the closer to the coast the sea level decreases
the friction between the sea bed and the waves increases
causing the waves to gain height
example of where a tsunami took place
japan
initial earthquake was 9 on richter scale
2011
around 19,500 deaths
focus was around 30km below the floor of the western pacific ocean
what are aftershocks and how long can they last for?
seismic waves shaking as under the ground crust is readjusting
days weeks months years
what is liquefaction?
when violently shaken, soils with a high water content lose their mechanical strength and behave like a fluid
example of when liquefaction took place
new zealand, christchurch
2011
10s of thounsands properties damaged
6.3 magnitude richter scale
what happens during an avalanche or landslide?
mass movement when there is a slope failure as a result of the ground shaking in soil or snow will cause it to become unstable
example of an avalanche
nepal
2015
richter scale 7.9
19 killed by avalanche at mount everests camp
around 9,000 killed
(avalanches) blocking roads hampering the relief effort
what was the worlds deadliest avalanche?
1970 Ancash earthquake (the great peruvian earthquake)
peru
the most catastrophic disaster in peru ever
up to 70,000 casualties
Haiti as a mini case study
7.0 magnitude earthquake struck Haiti on 12th January 2010, with an epicentre 25 km southwest of Port-au-Prince, the capital.
lies on the Enriquillo-Plantain Garden Fault, which is a conservative plate boundary between the Caribbean Plate and the North American Plate.
An estimated 230,000 people were killed
300,000 injured
1.5 million left homeless.
70% of buildings in Port-au-Prince collapsed, including government buildings, hospitals, and 4,000 schools.
total economic loss was around $8 billion, equivalent to 120% of Haiti’s GDP at the time.
the UN launched an appeal of $550 million for food
Despite international aid (e.g., $13 billion pledged globally), corruption and lack of coordination delayed recovery efforts.
cholera outbreak in late 2010 (linked to UN peacekeepers) killed over 10,000 people and infected 820,000.
Vulnerability Factors – Haiti is an LIC with poor building regulations, high population density, and a weak government, making it highly vulnerable to disasters.
Aftershocks & Secondary Impacts – Multiple aftershocks (up to 6.1 magnitude) worsened damage, and landslides blocked roads, limiting aid distribution.
Long-Term Recovery – By 2020, over 30,000 people were still in displacement camps, and Haiti remained highly vulnerable to future hazards, including the 7.2 magnitude earthquake in 2021.
