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Geo of Hazards > Lecture #7 - Earthquakes > Flashcards

Lecture #7 - Earthquakes Flashcards

1
Q

What are quakes the result of?

A

Rupture of rocks along a fault line

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2
Q

How is the energy of a quake released as?

A

Seismic waves

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3
Q

What is the difference between the Epicentre and the Focus?

A

Epicentre is where the earthquake actually happens below ground
Focus is the place on the surface directly above the epicentre

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4
Q

How do we measure earthquakes?

A

Moment Magnitude Scale

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5
Q

What is the Moment magnitude scale determined by?

A
  • area ruptured
  • amount of movement along a fault
  • The elasticity of the crust
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6
Q

What is the Modified Mercalli Intensity Scale?

A
  • Qualitative scale based on the damage to structures and the affect on people.
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7
Q

What causes the sudden movement along the fault ?

A
  • Stress builds up, causing inconsistent movement in the fault.
  • When stress is greater, it causes the fault to jump forward, causing and earthquake
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8
Q

Where to seismic wave originate?

A

At the focus

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9
Q

What are Blind faults?

A

Faults located below the surface

-aka can’t see em

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10
Q

What are the 2 types of faults based on the directions of the displacement of rock or sediment?

A
  1. Strike -Slip fault

2. Dip Slip Fault

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11
Q

What are the 3 types of dip slip faults?

A
  1. Reverse
  2. Thrust
  3. Normal
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12
Q

What are the 3 categories that faults can fall into?

A
  1. active
  2. Potentially active
  3. Inactive
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13
Q

What is a Tectonic Creep?

A

The slow movement of rock or sediment along fracture caused by stress

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14
Q

In what places to seismic waves travel?

A

Through the body of the earth and along the surface

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15
Q

What are body waves?

A

Include P and S waves

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16
Q

What are P waves?

A

Primary waves

  • move fast
  • push pull motion
  • Can travel through solid and liquids
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17
Q

What are S waves?

A

Secondary waves

  • move slowly
  • Up and down motion
  • Can only travel through solids
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18
Q

What are surface waves?

A

Seismic waves that form when P and S waves reach earths surface and then move along it
-move slower than body waves

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19
Q

What are some factors that determine what shaking people feel from ta quake?

A
  • Magnitude
  • Distance to epicentre
  • Focal depth
  • Direction of the rupture
  • Soil and rock type
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20
Q

What happens to shaking as you increase distance form the epicentre?

A

-Shaking decreases

21
Q

How do you calculate where the epicentre is?

A

Triangulation

  • measured n 3 different seismographs
  • where they all intercept is where it is
22
Q

What happens to the waves as they spread outwards?

A

They become less intense

23
Q

What is the relationship between focal depth and shaking?

A

As focal depth increases, the shaking decreases

24
Q

what is directivity?

A

Quake energy is focused in the direction f the rupture

25
Q

relationship between ground motion and hetero/homogeneous soils?

A

Homogenouse can transmit energy more quickly
Heterogenous slows down the energy
-mountians can also slow down the structure

26
Q

What is Amplification?

A

An increase in ground motion during an earthquake

27
Q

Can 2 quakes at the same magnitude have the same impact?

A

Depending on where they are they can have very different impacts

28
Q

What is the Earthquake cycle?

A

Hypothesis that explains successive earthquakes on a fault

-Strain drops abruptly after an earthquake and then slowly builds back up

29
Q

What are the 3 stages in a typical cycle?

A
  • inactive period
  • Strain produces minor
  • foreshock prior to the big shock
30
Q

What is a fore shock?

A

a small to moderate quake that occurs before and in the same general area as the main shock

31
Q

What are plate boundary earthquakes?

A

Quakes that occur o faults separating lithospheric plates

- can have strike slip, thrust and normal

32
Q

What is a strike slip quakes?

A

occur along transform faults where plates slide horizontally past each other

33
Q

What is a thrust quake?

A

Occur on faults that separate converging plates

34
Q

What is normal fault quake?

A

occur on faults associated with divergent plate boundaries

35
Q

What are interpolate quakes?

A

A quake on a fault in the interior of a continent.

-far from a plate boundary

36
Q

What are the 2 active interpolate zones?

A

Mississippi River valley

St Lawrence River valley

37
Q

What are the 2 regions in the US that could have a high M value?

A
  • St. Louis

- Memphis

38
Q

What are some Primary effects of quakes?

A
  • Ground shaking

- Surface Rupture

39
Q

What are some Secondary effects?

A
  • Liquefaction
  • Land level change
  • Landslides
  • Fires
  • Tsunamis
40
Q

What is a ground rupture

A

displacement along faults causes cracks in the surface

41
Q

What is a Fault Scarp?

A

A linear escarpment at earth surface formed by movement along a fault during a quake

42
Q

What is Liquefaction?

A

The transformation of water saturated sediment from solid to liquid

43
Q

What are landslides?

A

Ground motion produced by a quake can cause rock and sediment to move downslope

44
Q

How can quakes cause fires?

A

the sock can sever power lines and gas lines which can catch on fire

45
Q

What are the natural service functions of quakes?

A
  • Provide pathways for the downward flow of surface water
  • Can channel water to surface discharge points
  • new material resources can be exposed
46
Q

How can humans produce quakes?

A
  • Weight of damns can create new faults
  • Injecting liquid waste into the earth
  • Testing nuclear weapons
47
Q

How do we estimate seismic risk?

A

By using hazard maps

48
Q

What are the 4 precursors to quakes?

A
  1. The pattern and frequency of earthquakes (based on foreshocks and micro earthquake)
  2. Land level changes
  3. Seismic Gaps
  4. Physical and chemical changes
49
Q

How much times does the current earthquake warning systems give us?

A

15-30 seconds

- all forecasts have to be scientifically received before they are forecasted

Geo of Hazards (12 decks)

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