Chapter 7 - Earthquakes

Front 1

Fault scarp

Back 1

The exposed part of the fault plane during a fault rupture.

Front 2

Fault trace

Back 2

The point where the overhang makes contact with the fault scarp in a fault rupture.

Front 3

Shallow Earthquakes

Back 3

< 70 km (over 90% of quake energy is released in upper 100 km)

Front 4

Intermediate Earthquakes

Back 4

70-300 km

Front 5

Deep Earthquakes

Back 5

300-670 km

Front 6

P-waves (Primary Waves)

Back 6

- Body waves
- Push-pull
- Arrive first

Front 7

S-waves (Secondary Waves)

Back 7

- Body waves
- Side-to-side
- Arrive after P-waves

Front 8

Rayleigh Waves

Back 8

"Ground roll" surface waves that behave like rolling ocean waves, causing the ground to move in an elliptical path

Front 9

Love Waves

Back 9

Surface waves that move from cause the ground to move from side to side in the horizontal plane perpendicular to the direction of the wave

Front 10

Intensity

Back 10

A measure of an earthquake's effect on people and buildings

Front 11

Magnitude

Back 11

A measure of the energy released during an earthquake

Front 12

Four effects of earthquakes

Back 12

1) Ground motion
2) Fire
3) Landslides
4) Liquefaction

Front 13

Four Factors affecting intensity

Back 13

1) Geology
2) Construction of buildings
3) Distance
4) Magnitude

Front 14

Good Construction (in terms of quake resistance)

Back 14

Strong, flexible, tied together wood / steel frame

Front 15

Bad Construction (in terms of quake resistance)

Back 15

Unreinforced masonry, "soft" ground floors

Front 16

Richter Magnitude (6 characteristics)

Back 16

- Measures the maximum wave amplitude.
- Corrected for distance.
- No units.
- No upper and lower limit.
- Used to calculate the energy released.
- Good for events < 7.5 recorded close to epicenter (< 300 km)

Front 17

Problems with large, distant earthquakes

Back 17

- More energy is transferred in long wavelength, low amplitude waves.
- Richter measurement does not measure low amplitude waves (amplitude is saturated at about 7.5)

Front 18

Moment Magnitude

Back 18

- Determined from rock strength, surface area, and average fault offset
- Can be estimated with seismograms

Front 19

Exponential Magnitude Scales

Back 19

Below 7, one unit increase (i.e. from 6.0 to 7.0) = 10 times the shakeing

Front 20

Energy change for a one unit increase in magnitude

Back 20

- One unit increase (i.e. from 6.0 to 7.0) = 30 times the energy.
- Two unit increase = 900 times the energy

Front 21

Merecalli Intensity

Back 21

Measures earthquake effects on a scale of I to XII

Front 22

Earthquake Effects

Back 22

- Ground Motion (always)
- Fault Rupture (always)
- Subsidence and Uplift (sometimes)

Front 23

Liquefaction

Back 23

- Transformation of a saturated soil to a fluid.
- Caused by a rapid increase in pore-fluid pressure.

Front 24

Earthquake Effects - Ground Motion (always)

Back 24

- Fire (sometimes)
- Landslides (sometimes)
- Liquefaction (sometimes)

Front 25

Earthquake Effects - Fault Rupture (always)

Back 25

- Fault trace / scarp (sometimes)

Front 26

Earthquake Effects - Subsidence / Uplift (sometimes)

Back 26

- Tsunami (rarely)

Front 27

Tsunami vs. Wind Waves - Sources

Back 27

Tsunamis - Caused by large earthquakes that disturb the sea floor, submarine landslides, or volcanic explosions.

Wind Waves - wind

Front 28

Tsunami vs. Wind Waves - Wavelength

Back 28

Tsunami - up to 100 miles

Wind Waves - up to 400 m

Front 29

Tsunami vs. Wind Waves - Speed

Back 29

Tsunami - up to 450 mph in deep water

Wind Waves - up to 90 mph in deep water

Front 30

Tsunami vs. Wind Waves - Height (breaking)

Back 30

Tsunami - 15-30 meters (50-100 feet)

Wind Waves - 0.6 to 3.0 meters (up to 50 feet in hurricanes)

Front 31

Three possible results of unconsolidated / saturated sediment during quakes

Back 31

1) Increase in wave amplitude; greater resonance potential
2) Waves slow down (longer duration)
3) Potential liquefaction