Lecture #7 - Earthquakes Flashcards Preview

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Flashcards in Lecture #7 - Earthquakes Deck (49):
1

What are quakes the result of?

Rupture of rocks along a fault line

2

How is the energy of a quake released as?

Seismic waves

3

What is the difference between the Epicentre and the Focus?

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

4

How do we measure earthquakes?

Moment Magnitude Scale

5

What is the Moment magnitude scale determined by?

-area ruptured
-amount of movement along a fault
-The elasticity of the crust

6

What is the Modified Mercalli Intensity Scale?

- Qualitative scale based on the damage to structures and the affect on people.

7

What causes the sudden movement along the fault ?

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

8

Where to seismic wave originate?

At the focus

9

What are Blind faults?

Faults located below the surface
-aka can't see em

10

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

1. Strike -Slip fault
2. Dip Slip Fault

11

What are the 3 types of dip slip faults?

1. Reverse
2. Thrust
3. Normal

12

What are the 3 categories that faults can fall into?

1. active
2. Potentially active
3. Inactive

13

What is a Tectonic Creep?

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

14

In what places to seismic waves travel?

Through the body of the earth and along the surface

15

What are body waves?

Include P and S waves

16

What are P waves?

Primary waves
-move fast
-push pull motion
-Can travel through solid and liquids

17

What are S waves?

Secondary waves
-move slowly
-Up and down motion
-Can only travel through solids

18

What are surface waves?

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

19

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

-Magnitude
-Distance to epicentre
-Focal depth
-Direction of the rupture
-Soil and rock type

20

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

-Shaking decreases

21

How do you calculate where the epicentre is?

Triangulation
-measured n 3 different seismographs
-where they all intercept is where it is

22

What happens to the waves as they spread outwards?

They become less intense

23

What is the relationship between focal depth and shaking?

As focal depth increases, the shaking decreases

24

what is directivity?

Quake energy is focused in the direction f the rupture

25

relationship between ground motion and hetero/homogeneous soils?

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

26

What is Amplification?

An increase in ground motion during an earthquake

27

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

Depending on where they are they can have very different impacts

28

What is the Earthquake cycle?

Hypothesis that explains successive earthquakes on a fault
-Strain drops abruptly after an earthquake and then slowly builds back up

29

What are the 3 stages in a typical cycle?

- inactive period
-Strain produces minor
-foreshock prior to the big shock

30

What is a fore shock?

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

31

What are plate boundary earthquakes?

Quakes that occur o faults separating lithospheric plates
- can have strike slip, thrust and normal

32

What is a strike slip quakes?

occur along transform faults where plates slide horizontally past each other

33

What is a thrust quake?

Occur on faults that separate converging plates

34

What is normal fault quake?

occur on faults associated with divergent plate boundaries

35

What are interpolate quakes?

A quake on a fault in the interior of a continent.
-far from a plate boundary

36

What are the 2 active interpolate zones?

Mississippi River valley
St Lawrence River valley

37

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

-St. Louis
-Memphis

38

What are some Primary effects of quakes?

-Ground shaking
-Surface Rupture

39

What are some Secondary effects?

-Liquefaction
-Land level change
-Landslides
-Fires
-Tsunamis

40

What is a ground rupture

displacement along faults causes cracks in the surface

41

What is a Fault Scarp?

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

42

What is Liquefaction?

The transformation of water saturated sediment from solid to liquid

43

What are landslides?

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

44

How can quakes cause fires?

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

45

What are the natural service functions of quakes?

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

46

How can humans produce quakes?

-Weight of damns can create new faults
-Injecting liquid waste into the earth
-Testing nuclear weapons

47

How do we estimate seismic risk?

By using hazard maps

48

What are the 4 precursors to quakes?

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

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

15-30 seconds
- all forecasts have to be scientifically received before they are forecasted