Impacts of earthquakes

Question 1

Primary

Answer 1

• Ground shaking
• Ground rupture or displacement
• Landslides/ avalanches
• Liquefaction
• Human impacts
• Tsunami

Question 2

Ground shaking

Answer 2

• Buildings - damaged

- May cause landslides, mudslides

Question 3

Landslides/ avalanches

Answer 3

• Slope failure - ground shaking

Question 4

Liquefaction

Answer 4

• Mixing of sand or soil and groundwater
• During shaking
• Buildings sink
• Water + soil = ground is soft and acts like quick sand
• Shaking increases pore pressure = reduces effective stress - reduces the shear strength of the soil.
• Ground firms up after earthquake and water settled back to usual.
• HAZARD - groundwater areas and sand soils

Question 5

Human impact

Answer 5

• Depends on population density and distance from epicentre

Question 6

Tsunami

Answer 6

• Enormous sea waves generated by disturbances on the sea floor

Question 7

How a tsunami forms

Answer 7

• Earthquakes and ocean floor volcanoes = lot of water to be displaced in a short space of time = massive amounts of energy
• Energy = oscillatory waves over ocean surface at speeds as fast as 500mph
• Wavelength of tsunami continues to grow = small height waves may travel quickly but may pass undetected.
• Waves approach coastline - slowed dramatically by friction due to the collision = velocity lesses, but wavelength shortens and amplitude increases.
• Giant waves collide with shore = damage
• Sea recedes from coast before advancing = DRAWDOWN which happens minutes before.

Question 8

Aftershocks

Answer 8

• Earthquakes following on from main event
• May last for months
• Generated by earth settling back after the disruption of the first displacement.