Earthquakes and the earth's interior

Question 1

Stress

Answer 1

is the force or load on an object

Question 2

Strain

Answer 2

is the response to that load

- deformation i.e elongation, compression or distortion

Question 3

Earthquake rupture 0 seconds

Answer 3

rupture expands circularly on fault plane, sending out seismic waves in all directions

Question 4

Earthquake rupture 5 seconds

Answer 4

rupture continues to expand as a crack along the fault place. when rupture front reaches the surface, displacements occur along the fault trace and rocks at the surface begin to rebound from their deformed state

Question 5

Earthquake rupture 10 seconds

Answer 5

rupture front progresses down the fault plane, reducing the stress and allowing rocks on either side to rebound. seismic waves continues to be emitted in all directions as the fault propagates

Question 6

Earthquake rupture 20 seconds

Answer 6

rupture has progressed along the entire length of the fault. the fault has reached its maximum displacement and the earthquake stops

Question 7

Normal faults (constructive)

Answer 7

tension forces as plates move apart, one side drops down relative to another, formation of waterfall, river catchment disruptions

Question 8

Thrust faults (destructive)

Answer 8

Compression fault (Reverse fault) shortening of the crust, sediments are piled up on each other, rocks rises up

Question 9

Strike-slip fault (conservative)

Answer 9

Shearing forces, loch ness lake along these faults, one plate sliding past the other

Question 10

Focus

Answer 10

where the earthquake begins (immediate stress)

Question 11

Epicentre

Answer 11

point on earths surface directly above focus

Question 12

P waves (primary)

Answer 12

• compressional waves, can move through solid and liquid, fastest waves
• wave energy moving thorough, squashing and stretching blocks
• push the earth

Question 13

S waves (secondary)

Answer 13

• shear waves, cannot move through liquid, slower waves
• wave shadow zone (105o), evidence for liquid outer core
• shake the ground

Question 14

Body waves

Answer 14

move through structure of the earth, greater than magnitude 5 then the waves travel through earth (big enough o travel trough globe)

Question 15

Rayleigh waves

Answer 15

up and down motion, cause buildings to break and collapse

Question 16

love waves

Answer 16

more of a lateral movement, side to side, cause water bridges to collapse (topple over)

Question 17

Seismographs

Answer 17

designed to detect horizontal movement

Question 18

Refraction

Answer 18

waves change their direction depending on relative velocity: the bend into the higher velocity material

Question 19

Mercalli scale

Answer 19

measures destruction of earthquake, no damage to total obliteration

Question 20

wave movement through/on earth

Answer 20

seismic wave bounce off (reflect) or bend (refract) at discontinuities reflecting major changes in rock properties such as rock density

Question 21

Summary

Answer 21

• waves can travel directly through the earth, or be refracted, reflected or attenuated
• changes in wave velocity through the mantle generally indicate increasing density with depth (other variations indicate convection in mantle)