1.12 - Shaken and Stirred

Question 1

How many types of seismic wave are there?

Answer 1

4

• Primary waves
• Secondary waves
• Love waves
• Rayleigh waves

Question 2

What are the 4 types of seismic waves called?

Answer 2

Primary (P), Secondary (S), Love (L), and Rayleigh waves.

Question 3

What are the characteristics of P-waves?

Answer 3

• Have a short wavelength and travel fast through both liquid and solid rock.

Question 4

How do P-waves move?

Answer 4

Waves push and pull in the direction of travel to create compressional and extensional zones.

Question 5

What are the characteristics of S-waves?

Answer 5

• Slower than P-waves and only travel through solid rock (not liquid)

Question 6

How do S-waves move?

Answer 6

Longer wavelength and movement is at right angles to direction of travel (vertical).

Question 7

What are the characteristics of L-waves?

Answer 7

Slowest but most destructive waves. Only move at the surface.

Question 8

How do L-waves move?

Answer 8

They have the largest amplitude and shake the ground from side to side (horizontal) as the wave travels forward.

Question 9

What are primary effects of an earthquake?

Answer 9

Primary effects are things that happen as a direct result of an earthquake.

Question 10

Examples of primary effects of an earthquake?

Answer 10

• Ground shaking, which causes buildings, bridges, roads and other infrastructure to collapse.
• Crustal fracturing, the energy released causes crust to crack and land to be displaced vertically.

Question 11

What are secondary effects of an earthquake?

Answer 11

Those that are indirectly caused by earthquakes, often causing much more damage than the initial shaking.

Question 12

Examples of secondary effects of an earthquake?

Answer 12

• Landslides, shaking places rock slopes under increased stress which could lead to failure.
• Liquefaction, surface rocks lose strength in violent shaking and become more liquid than solid, thus losing its ability to support building foundations and cars (like quicksand).

Question 13

What are aftershocks and why are they significant to response and recovery?

Answer 13

Other smaller earthquakes can continue to occur whilst the fault ‘settles down’ or readjusts to the initial release of strain.
They can significantly hamper response and recovery, particularly if larger than expected (e.g. Christchurch 2011). Can cause more damage.

Question 14

What are ways scientists can predict earthquakes and are they accurate?

Answer 14

• Although very difficult to predict accurately, foreshocks (those that happen before the main one) are being looked at to provide warning signs (precursors) for a potential earthquake.
• Animal behaviour could be a sign
• P-waves can be useful to trigger early warning systems and aid immediate response (particularly if the epicentre is far away).

Question 15

What was the name of the ocean between the Indian and Asian land masses before they collided?

Answer 15

The Tethys Ocean

Question 16

How long ago did India and Asia collide?

Answer 16

50 million years ago.

Question 17

What was created due to the collision?

Answer 17

The Himalaya mountain range.

Question 18

What is this type of boundary called?

Answer 18

Collision boundary.

Question 19

Why do mountain ranges form at collision boundaries?

Answer 19

The tectonic plates are of the same density as each other (both continental plates), so are pushed, or folded, together rather than subduction.

Question 20

Define ‘Liquefaction’

Answer 20

It is the phenomenon where shaking from the earthquake destabilises the soil by increasing the space between grains; with its structure lost, the soil flows like a liquid.