seismic hazards

Question 1

what are seismic waves

Answer 1

vibrations in the earths crust

Question 2

what do seismic waves cause

Answer 2

-earthquakes
-sudden movements along fault lines

Question 3

what is the focus

Answer 3

the precise location of an earthquake within the crust

Question 4

what is the epicentre

Answer 4

the point on the surface immediately above the focus, this is where we see the most destruction

Question 5

what are primary waves

Answer 5

they are the fastest, they reach the surface first. high frequency, they travel through both the mantle and the core to the opposite side of the earth

Question 6

what are secondary waves

Answer 6

they are half as fast as primary waves, therefore reach the surface next, they are high frequency but shake like a skipping rope, they can travel through the mantle but not the core so they cannot be measured at a point opposite the focus or epicentre

Question 7

what is liquefaction

Answer 7

-secondary seismic hazard
-liquefaction occurs in land with loose sediment which is waterlogged
-during an earthquake and the movement it causes the loose sediment to compact together moving the water out
-this causes things to sink

Question 8

what is a tsunami

Answer 8

-secondary seismic hazard
-giant sea wave generated by shallow focus underwater earthquakes, volcanic eruptions and large landslides into the sea
-they have a long wavelength (often over 100m) and low wave height (under 1 m) in the open ocean
-they travel quickly but on reaching the shallow water bordering land they increase in height
-a wave trough forms in front of the tsunami where sea level is reduced