3.1.3:Earthquakes: processes, hazards, impacts Flashcards
Elastic rebound
As the fault moves, shockwaves produced are felt as earthquakes
Focus
The point of break where an earthquake begins in the crust
Primary (p) waves
Vibrations caused by compression
They spread out from the earthquake fault
travel through solid rock (Earth’s core) and liquids (oceans)
Secondary (s) waves
travel at half the speed of p waves
can’t travel through liquids = lots of earthquake damage
vibrate at right angles to the direction of travel
Ground movement and shaking
surface seismic waves represent the most severe threat to humans
interlocking of s and p waves near the epicentre = where the most damage should occur depending on surface material
Liquefaction
secondary hazard
Unconsolidated ground is exposed to shaking and the water rises to the surface
Waves
4 types associated with earthquakes
Primary (p)
Secondary (s)
Rayleigh (r)
Love (l)
Rayleigh (r) waves
Surface waves and their materials follow an elliptical path in the direction of propagation and partly in a vertical wave
Love (l) waves
Similar to r waves but move faster and have vibrations solely in the horizontal plane
often generate the most damage
Epicentre
Point above the focus on the Earth’s surface
Depth
3 groups
deep focus
intermediate focus
shallow focus
Shallow focus
Most common and causes the most damage
0-70km
Intermediate focus
70-300km
Deep focus
300-700km
Causes of liquefaction
-poorly compacted sands and silts situated at depths less than 10m below surfaced are most affected when saturated
