Flashcards in Seismic Hazards Deck (7)
What is seismicity?
Seismicity is the earth shaking, can be human induced
How do seismic waves form?
- pressure builds where two plates meet
- sudden pressure release due to rock failure
- waves cause the ground to shake
- intensity of shaking affected by focus depth
How do tsunamis form?
- form at subduction zones, where oceanic plate is forced down due to plate tectonic forces
- plate lowers into mantle, causing overriding plate to be distorted
- there is a buildup of energy until it exceeds frictional forces between plates
- as a result, overriding plate snaps back into unrestrained position
- gives a push to overlying water, displacing it and it races away from epicentre
What is liquefaction?
This is the mixing of sand or soil and groundwater during the shaking of a earthquake. It causes the ground to become soft and unstable.
What are landslides?
Destabilising of cliffs or slopes as a result of ground shaking. Common in highland areas.
Where do seismic events occur?
They occur close to plate margins as this is where a lot of ground movement occurs.