Seismic Hazards Flashcards
On average, how many people die a year from seismic hazards?
63,000
Why do earthquakes occur?
The movement of tectonic plates cause pressure to build up in the Earth’s crust. When the pressure is released, a series of tremors (earthquakes) occur
What kind of earthquakes occur at continental boundaries?
Shallow focus. A result of tensional forces in the crust. Tend to happen at mid ocean ridges so are barely a risk to people
What kind of earthquakes occur at destructive boundaries?
Deep focus earthquakes. Occur at the benioff zone
What is the benioff zone?
The zone where earthquakes tend to occur as the oceanic crust is subducted underneath at a destructive boundary
What % of earthquakes happen at margins?
90%
What are primary hazards of earthquakes?
Shockwaves
What are body waves?
Travel through the Earth. Can be divided into P or S waves.
P waves travel through solid and liquid ar 5.5km/s
S waves not through liquids at 3km/s
What are surface waves?
Travel along the Earth’s surface. The ones we feel (dangerous waves)
What are surface waves?
Travel along the Earth’s surface. The ones we feel (dangerous waves)
What is unconsolidated sediment?
Loosely arranged particles of sediment that are not joined together
What are the secondary hazards of earthquakes?
Liquefaction, landslides/avalanches, falling rocks, tsunamis, destroyed buildings
What controls the impacts of earthquakes?
The magnitude and the vulnerability of the people
What are the short term impacts of earthquakes?
Collapsed buildings. Destroyed infrastructure. Pipes burst. Diseases
How many deaths are from collapsing buildings in earthquakes?
¾ of all deaths
