Seismicity - Causes of Earthquakes

Question 1

What builds up within rocks?

Answer 1

stress

Question 2

What happens when pressure is released suddenly?

Answer 2

intense shaking that lasts a few seconds

Question 3

What is the focus?

Answer 3

the point where the pressure is released within the crust

Question 4

What is the epicentre?

Answer 4

the point immediately above the focus on the earths surface

Question 5

What are other causes of earthquakes?

Answer 5

reactivation of old fault lines, subsidence, pressure on surface rocks

Question 6

What is the depth of a shallow-focus?

Answer 6

0-70km deep

Question 7

What is the depth of a intermediate focus?

Answer 7

70-300km deep

Question 8

What is the depth of a deep focus?

Answer 8

300-700km deep

Question 9

What focus causes the greatest damage and what % does it account for all earthquake energy released?

Answer 9

shallow-focus, 75%

Question 10

Whats another name for P waves?

Answer 10

primary waves

Question 11

Whats another name for S waves?

Answer 11

secondary waves

Question 12

Whats another name for L waves?

Answer 12

surface waves

Question 13

How fast do P waves travel?

Answer 13

5.5km/second

Question 14

Which direction do P waves vibrate?

Answer 14

in direction of travel

Question 15

What can P waves travel through?

Answer 15

solids and liquids

Question 16

Are P waves compressional?

Answer 16

yes

Question 17

What speed do S waves travel at?

Answer 17

3km/second

Question 18

Which direction do S waves vibrate?

Answer 18

at right angles to the direction of travel

Question 19

What can S waves travel through?

Answer 19

only solids

Question 20

Do L waves travel near the grounds surface?

Answer 20

yes

Question 21

In which direction do L waves vibrate?

Answer 21

at right angels to the direction of the wave

Question 22

What type of wave is the most damaging and why?

Answer 22

L waves, they travel up and down and side to side

Question 23

Do L waves travel quickly?

Answer 23

no they travel slowly near the grounds surface

Question 24

What are the slowest waves and in which direction do they move?

Answer 24

Rayleigh waves, move in a rollin motion

Question 25

Where do most earthquakes occur?

Answer 25

along plate boundaries

Question 26

Which plate boundary are the most powerful earthquakes associated with?

Answer 26

convergent plate margins

Question 27

What happens at conservative margins?

Answer 27

the boundary is marked by a fault a movement along it causes an earthquake e.g.. San Andreas fault