Earthquakes

Question 1

Name five components of the anatomy of an earthquake

Answer 1

Fault, Hypocentre/ Focus, Epicentre, Plates and Seismic waves

Question 2

Describe the fault

Answer 2

A fracture in rocks that make up the earth’s crust

Question 3

Describe the epicentre

Answer 3

The point at the surface of the earth directly above the focus

Question 4

Describe the hypocentre/ focus

Answer 4

The point within the earth where an earthquake rupture starts

Question 5

Describe the plates

Answer 5

Massive rocks that make up the outer layer of the earth’s surface and whose movement along faults triggers earthquakes

Question 6

Describe seismic waves

Answer 6

Waves that transmit the energy released by an earthquake

Question 7

What two scales measure the magnitude of a tectonic event?

Answer 7

Richter scale and Moment Magnitude Scale

Question 8

How does the richter scale measure magnitude?

Answer 8

Arrival times of P and S waves, amplitude of the S wave and distance from the epicentre

Question 9

How does the Moment Magnitude scale measure magnitude?

Answer 9

Energy released by all shock waves and area and rupture of movement (more accurate)

Question 10

What does logarithmic mean?

Answer 10

The scales go up with each level being ten times greater than the level below

Question 11

What scale measures the intensity of an earthquake?

Answer 11

The Mercalli scale

Question 12

What does the Mercalli scale use to measure intensity?

Answer 12

Amount of damage caused by seismic waves but local conditions can modify the correlation between intensity and damage

Question 13

Describe scale 1,3,5,7,10 and 12

Answer 13

1 - Felt by almost no one
3 - Tremours noticed by many but not realised as an earthquake
5 - People awakened and trees/poles swaying
7 - Poorly built structures severely damaged
10 - Ground is badly cracked
12 - Total destruction

Question 14

Describe scales 2.5, 4.5, 6 and 8+

Answer 14

2.5 - Generally not felt
4.5 - Some local damage
6 - Destructive
8+ Great

Question 15

Describe primary waves

Answer 15

Vibrations caused by compression, they spread quickly from the fault at a rate of 8km/ second

Question 16

Describe secondary waves

Answer 16

Move slowly at approx. 4km/ second and travel in right angles to the direction of travel but unlike P waves cannot move through liquids

Question 17

What are body waves?

Answer 17

P and S waves

Question 18

Describe love (Q) waves?

Answer 18

Waves that travel on the surface of the earth with vibrations in the horizontal plane with a high amplitude and moves from side to side

Question 19

Describe rayleigh waves?

Answer 19

Vibrations that travel through the earth’s surface in a rolling motion that moves the ground up, down and side-to-side.

Question 20

Name the primary hazards of an earthquake

Answer 20

Ground shaking and crust fractures

Question 21

Name the secondary hazards of an earthquake

Answer 21

Liquefaction and landslides

Question 22

Describe liquefaction

Answer 22

Shaking causes ground rocks to lose strength and become more liquid in composition so the subsoil loses the ability to support foundations of buildings and infrastructure which can disrupt gas pipes and cause fires

Question 23

Describe landslides

Answer 23

Shaking places stress on slopes usually a magnitude over 4.0 will cause landslides and this risk is increased by liquefaction

Question 24

Describe the 2003 Bam earthquake

Answer 24

• 7km hypocentre
• 5.26am local time
• Ancient buildings over 2000 years old
• 3 hospitals destroyed and 20% of professionals killed
• Winter so many trapped victims died of hypothermia

Question 25

Describe the 2015 Nepal earthquake

Answer 25

• 7.8 magnitude
• 9000 died
• 22,000 injured
• Half a million houses collapsed
• Multiple hazard zone

Question 26

Describe the 2010/11 New Zealand earthquakes

Answer 26

• Business activity rebounded rapidly after initial destruction
• Tourism decreased 40% in 2011/12
• Rebuild was largely insured
• Agriculture largely unaffected