U3L4

Question 1

why do earthquakes occur?

Answer 1

tectonic plate movement and the release of energy accompanying movement of rock along a fault cause earthquakes

Question 2

where do earthquakes occur?

Answer 2

at or near tectonic plate boundaries where stress has build up from rock grinding, colliding, and separating, which causes earthquakes when released.

Question 3

explain the difference between elastic rebound and elastic deformation

Answer 3

elastic rebound: rock returns to the exact original shape
elastic deformation: rock returns to almost its original shape.

Question 4

define the focus of an earthquake.

Answer 4

the place within earth along a fault where the first motion of an earthquake occurs. it’s the source of seismic waves.

Question 5

define the epicenter of an earthquake.

Answer 5

the place on earth’s surface right above the focus

Question 6

list 4 effects of earthquakes

Answer 6

• s waves/surface waves are released causing ground shaking
• offshore earthquakes may cause tsunamis
• shaking can collapse buildings, causing most of the injury and death
• can also cause fires, gas leaks, floods, polluted water, and dangerous debris

Question 7

how can soil type and rock structures affect how earthquakes affect an area?

Answer 7

geological variations or “site effects” can change the effects felt in different areas at the same distance from an epicenter. these variations include:
- softness of the soil or rock
- the total thickness of the sediment above bedrock

Question 8

define magnitude

Answer 8

measures how much energy is released by the earthquake

Question 9

define intensity

Answer 9

measures effects of the earthquake at earth’s surface

Question 10

define the moment magnitude scale

Answer 10

measures earthquake strength based off:
- the area of the fault that moves
- the average distance that the fault moves
- the rigidity of the rocks in the fault