Earthquakes

Question 1

Stress?

Answer 1

Force per unit area that is placed on a rock.

Question 2

Shear stress?

Answer 2

Forces are parallel but moving in opposite directions.

Conservative

Question 3

Confining stress?

Answer 3

Deeply buried rock is pushed down by the weight of the material above it. Rock cannot move, cannot deform.

Question 4

Compression?

Answer 4

Squeezes rocks together, causing them to fold or fracture.

Destructive, collision

Question 5

Tension

Answer 5

Rocks are pulled apart, and lengthen or break.

Constructive

Question 6

Strain?

Answer 6

Any change in volume or shape

Question 7

Elastic strain?

Answer 7

Reversible. Rock goes back to original shape if stress released.

Question 8

Ductile strain?

Answer 8

Irreversible. Rocks remains deformed even if stress stops.

AKA plastic deformation

Question 9

Fracture?

Answer 9

Rock has abruptly broken into distinct pieces. If pieces are offset (shifted in opposite directions) the fracture is a fault.

AKA rupture

Question 10

Moment magnitude scale?

Answer 10

Mo= μ x D x A

μ= rock rigidity
D= distance of fault rupture
A= faulted area (l x w)

Question 11

Is rock rigidity higher in the crust or mantle?

Answer 11

Mantle

Question 12

Largest magnitude earthquake?

Answer 12

Convergent fault
Greater fault width (subduction)
Mantle rigidity higher in upper subduction zone.

Question 13

When was the Denali Fault Earthquake?

Answer 13

2002

Question 14

DFE 2002- magnitude?

Answer 14

7.9

Question 15

How wide were cracks in Earth’s surface?

Answer 15

Up to 6.7 metres wide

Question 16

Damages?

Answer 16

$25 million (roads and bridges)
Sparsely populated area (damage minimal)

Question 17

Trans-Alaskan Pipeline facts

Answer 17

Carries 17% of US oil (10bn barrels)
Built to withstand 8 metres of movement (sliders)

Question 18

Body waves?

Answer 18

P wave (longitudinal)
S wave (transverse)

Spread several kilometres down.
Quicker- loses energy