Earthquakes

Question 1

Focus

Answer 1

the point underground where the earthquake originates from

Question 2

Epicentre

Answer 2

the area above ground that is ​directly above​ the focus

Question 3

Primary seismic waves (P waves)

Answer 3

• Travels through solids
• Compressional
• Vibrates in the direction of travel
• Travels at 4-8 km/s

Question 4

Secondary seismic waves (S waves)

Answer 4

-Vibrate at right angles to direction of travel
-Travels only through solid rocks
-Travels at 2.5 - 4 km/hr

Question 5

Love waves (L waves)

Answer 5

-Near to ground surface
-Rolling motion producing vertical ground movement
-Travels at 2-6 km/hr

Question 6

R waves

Answer 6

-Vertical and horizontal displacement -Travels at 1-5 km/hr
-Compressional

Question 7

What affects a location’s vulnerability?

Answer 7

geology, geographical location (whether the earthquake occurs near the sea or intraplate), education of locals, durability of buildings, mitigation

Question 8

Soil liquefaction

Answer 8

Affects poorly compacted sand and silt.
● Water moisture within the soil separates from the soil particles and rises to the
surface
● This can cause the soil to behave like a liquid, which can cause building subsidence
or landslides

Question 9

Landslides

Answer 9

The shaking caused by the earthquake can weaken or damage cliff faces, hills and snow material
● Unconsolidated material or loose rocks can collapse
● Landslides can travel several miles and accumulate material on the way.
● Risk varies with topography rainfall, soil and land use

Question 10

Tsunamis

Answer 10

When an oceanic crust is jolted during an earthquake, all of the water above this plate is displaced​, normally upwards
● This water is then pulled back down due to gravity. The energy is transferred into the water and travels through it like a wave.
● The water travels fast but with a low ​amplitude​ (height).
● As it gets closer to the coast, the sea level decreases so there is friction between the sea bed and the waves.
● This causes the waves to slow down and gain height, creating a wall of water that is on average 10 feet high, but can reach 100 feet.

Japan tsunami 2011

Question 11

Impact of tsunamis depends on…

Answer 11

Population density​ of area hit, if the population is higher than more people are likely to be affected
● Coastal defences​ (e.g. Tsunami waves)
● Duration of the event
● Wave amplitude and distance travelled
● Gradient of the ​continental shelf
● The shape of the land - ​bays​ will funnel and concentrate tsunami waves.
● Warning & Evacuation​ Systems
● Level of economic and human development