Earthquakes + Resultant Hazards

Question 1

Describe how earthquakes occur.

Answer 1

• when convection currents in asthenosphere continue to push plates that are stuck, so pressure builds up
• eventually, pressure is suddenly released, causing a jolting motion, which leads to shock waves spreading throughout ground

Question 2

What hazards result from Earthquakes?

Answer 2

• shaking
• landslides
• soil liquefaction
• tsunami

Question 3

Explain how shaking results from an earthquake.

Answer 3

• when built up pressure (stored as potential energy), from friction of 2 plates moving side by side, is suddenly released, generating shockwaves which vibrate throughout ground
• this causes shaking which can result in landslides + buildings + infrastructure collapsing

Question 4

Explain how landslides + avalanches result from an earthquake.

Answer 4

• when ground shakes, it disrupts stability of slopes
• eventually, large amounts of rock, soil + debris, or snow, lose their cohesion + move downhill
• this can damage infrastructure + buildings, damage envi. + threaten life

Question 5

Explain how soil liquefaction results from an earthquake.

Answer 5

• EQ causes shock waves to travel throughout ground, causing ground to shake
• this causes water pressure, in water-saturated soil, to inc between soil particles, dec friction
• meaning soil becomes weaker, + causes it to act like a liquid, so can’t support foundations of buildings, causing irreversible damage
• it can also cause underground pipes to fracture or vehicles to sink

Question 6

Explain how tsunamis result from an earthquake.

Answer 6

• when oceanic crust is jolted during an EQ, shockwaves cause a large volume of water above plate to be displaced
• this generates waves w a low amplitude, that travel at high speeds across deep ocean
• as wave travels towards coast, water becomes shallower + friction w bed causes wave to slow down, forcing wave to compress + inc in height, resulting in a several meter high wave

Question 7

Describe how the magnitude of earthquakes are measured.

Answer 7

• Richter scale is used to measure strength of shockwaves generated by an EQ
• also Mercalli scale is used to rate destruction caused
• magnitude depends on depth of focus