Week 5, When the Earth Shakes in Canada...

Question 1

Stick-slip friction occurs in the ______ period, stress exceeds this friction and we get another earthquake.

Answer 1

Stick-slip friction occurs in the inter-seismic period, stress exceed this friction and we get another earthquake.

Question 2

The _____ of seismic waves is related to the material they travel through.

Answer 2

The velocity of seismic waves is related to the material they travel through.

Question 3

What can affect the velocity of a seismic wave?

Answer 3

Material
Temperature
Pressure

Question 4

3 factors increase seismic hazard due to shaking

Answer 4

• Soil liquefaction
• Amplification
• Resonance

Question 5

Soil Liquefaction

Answer 5

Mixture when shaken starts acting like a fluid, buildings and people can sink into it.

Question 6

Amplification

Answer 6

Effect that includes the layering geometry of Earth.

When seismic waves travel very fast in hard rock they store a lot of energy, when the wave hits soft soil the amplitude increases. This is because the seismic wave must conserve energy, it can’t lose energy, so it must increase amplitude. It travels faster through hard rock and slower throw soft soils, waves passing from hard to soft material slow down, the amplitude increases for the wave to carry some energy.

Question 7

Resonance

Answer 7

Related to amplification

Soft soil sitting on hard bedrock, seismic waves lose a little of their energy as they are getting reflected and split off.

Question 8

Buildings are designed to withstand ___ shaking, but ____ shaking can do massive damage.

Answer 8

Buildings are designed to withstand vertical shaking. but horizontal shaking can do massive damage.

Question 9

Required safety level for buildings

Answer 9

No major damages in small earthquake

No structural damages in moderate earthquake

No collapse in largest expect earthquake

Question 10

Building Considerations for an Earthquake: Site Selection

Answer 10

Avoid slopes, or soft soil/fill

Don’t have different materials (different shaking characteristics) under one foundation.

Question 11

Building Considerations for an Earthquake: Foundation

Answer 11

Bolt structure to foundation to avoid slip in horizontal shaking.

Question 12

Building Considerations for an Earthquake: Building Materials

Answer 12

• Wood: Good, light, flexible
• Steel: Good, strong in tension, can fail in compression
• Masonry: Poor, heavy, weak in horizontal shaking
• Concrete: poor
• Adobe: Poor, heavy, weal
• Grass hut: Very good if the roof is attached

Question 13

Building Considerations for an Earthquake: Walls

Answer 13

Walls must be securely attached to floor/roof and strengthened.

Question 14

Building Considerations for an Earthquake: Base Isolation

Answer 14

Device on ground absorbs earthquake energy.