Chapter 9: Earthquakes and Earth's Interior

Question 1

Earthquakes/Seismic Waves

Answer 1

released when rock breaks (focus); they travel through the earth

Question 2

Stress

Answer 2

Force applied (by mantle convection)

Question 3

Strain

Answer 3

Resulting deformation

Question 4

Elastic Strain

Answer 4

Deformation up to elastic limit, impermanent

Question 5

Rupture

Answer 5

Creating faults, release earthquakes

Question 6

P-waves

Answer 6

Primary waves/ Compressional waves

• Goes through solids and liquids
• Travel the fastest

Question 7

S-waves

Answer 7

Secondary Waves/Shear Waves

• Travel through solids only
• 2/3 the speed of a P-wave

Question 8

Surface Waves

Answer 8

Travel the Earth’s surface

• Cause damage
• Travel the slowest

Question 9

Measuring Earthquakes

Answer 9

Size depends on energy stored as elastic strain (elastic rebound theory)

Question 10

Magnitude

Answer 10

Measure of energy released

• Richter scale, ranges from 0-9+
• A point represents 30x increase in energy

Question 11

Modified Mercalli Intensity

Answer 11

Measure of shaking (damage)

-Not always correlated w/ Richter scale

Question 12

Effects

Answer 12

Primary effect
-ground shaking by surface waves
Secondary effects
-fires
-floods: tsunami, dam rupture
-liquefaction (quick conditions)
-landslides

Question 13

Seismic Gaps

Answer 13

Segments of active faults where no earthquake has occured lately; therefore, elastic strain must be accumulating

Question 14

Precursors

Answer 14

• ground tilting
• swarms of small earthquakes (fore shocks)
• radon gas release
• groundwater level drops

Question 15

Mitigation of damage

Answer 15

Internal structure

• Focus are in upper 100km
• Outer layer is rigid, it’s the lithosphere

Question 16

Low Velocity Zone

Answer 16

S and P waves slow below 100km

-Non-rigid(plastic) asthenosphere

Question 17

S-wave Shadow Zone

Answer 17

S-waves don’t arrive here, can’t go around liquid outer core

-Proved the core of the earth is liquid