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EAS > Lecture 6: Earthquakes > Flashcards

Lecture 6: Earthquakes Flashcards

1
Q

What is an earthquake?

A

Shaking or vibration of the ground that represent a release of built up stress which occurs when rocks being deformed suddenly break along a fault

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2
Q

What is Elastic Rebound?

A

When the rocks snap back elastically to their previous dimensions after an earthquake

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3
Q

What is a Slip?

A

The distance of the displacement between two rocks after an earthquake

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4
Q

What are the 3 types of Faults?

A
  • Normal Fault
  • Thrusts/Reverse Fault
  • Shearing/Strike-slip Forces
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5
Q

What occurs in a Normal Fault?

A

Tension forces pull the two plates away from each other and one slides up and one slides down

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6
Q

What occurs Thrust Faults?

A

Two plates are pushed towards each other and one slides on top of the other

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7
Q

What occurs is Strike-slip faults?

A

Two plates slide past each other

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8
Q

What are strike slip faults due to?

A

Shearing stress

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9
Q

What are Normal faults due to?

A

Tensile Stress

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10
Q

What are thrust faults due to?

A

Compressive stress

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11
Q

What is the Focus?

A

The point on a fault at which the first movement or break occurs during an earthquake

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12
Q

What is the Epicenter?

A

The point on the earth’s surface directly above the focus is called the epicenter

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13
Q

What are Seismic waves?

A

When rocks slip suddenly and causes intense vibrations that travel outwards from the surface

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14
Q

What are the 3 types of Seismic waves?

A
  • P waves (compressional/primary)
  • S waves (shear/secondary)
  • Surface waves
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15
Q

What are P waves?

A

Waves that move parallel to the direction of movement 6-8km/s

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16
Q

In which medium do P waves travel faster in?

A

Solids

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17
Q

What are S waves?

A

Waves that move move perpendicular to the direction of movement (4-5km/s)

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18
Q

In what medium do S waves travel in?

A

Solids only

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19
Q

What are Surface waves?

A

Waves that are confined to the surface of the earth

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20
Q

What are the two types of surface waves?

A
  • Elliptical motion waves

* Sideways waves

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21
Q

What occurs in Elliptical motion waves?

A

The ground surface moves in a rolling, elliptical motion that dies down with depth between the surfar

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22
Q

What occurs in sidewats waves?

A

The ground shakes sideways with no vertical motion

23
Q

How do scientists use P,S and surface waves to pinpoint the location of an earthquakes?

A

They look at the timing difference of the waves to reach the seismographs and the magnitude to pinpoint the distance from which the earthquake originated

24
Q

Why are multiple seismograms from different location needed?

A

Because the data only tells us how far the earthquake is from the seismograph

25
Q

How many km is the mantle?

A

40 kms

26
Q

What is the order of the layers of the earth’s interior?

A
  • Crust
  • Mantle
  • Liquid Outer core
  • Solid Inner core
27
Q

What is the Radius of the earth?

A

6370 km

28
Q

What is the distance between the highest peak and the lowest trench?

A

20 km

29
Q

How are the speed of P and S waves affected with density?

A

As you get denser the faster the waves will travel

30
Q

How is the speed of P and S waves affects as they go from the Lithosphere to the Athenosphere?

A

Both of their speeds drop because the Asthenosphere is partially molten

31
Q

What happens to S waves as it travels through the liquid outer core?

A

They stop because S waves cannot travel through liquid

32
Q

What happens to P waves as they travel the liquid outer core?

A

The slow down because it is a less dense liquid

33
Q

What happens to P and S waves as they travel from the Asthenosphere from the lower mantle?

A

They speed up because the mantle is more dense

34
Q

What causes the large S wave shadow?

A

The inability of the S wave to travel through the liquid outer core

35
Q

What causes the P wave shadow?

A

The refraction of the of the P waves as they travel through the liquid outer core

36
Q

What rock is oceanic crust made of?

A

Basalt

37
Q

What rock is Continental crust made of?

A

Granite

38
Q

What rock is the Mantel made out of?

A

Peridotite

39
Q

How thick can the crust get?

A

Up to 70km

40
Q

What is an example of a Felsic rock of the Crust?

A

Granite

41
Q

What is an example of a Mafic rock in the crust?

A

Gabbro

42
Q

What are the densities of Felsic and Mafic rocks and the rocks of the Moho?

A
  • Felsic rocks have a lower density around 2.8g/cm3
  • Mafic rocks have a higher density around 2.9g/cm3
  • Moho rocks have the highest density of 3.5g/cm3
43
Q

What are Shallow earthquakes associated with?

A

Divergent boundaries and transform faults, as well as continents due to crustal movements

44
Q

What are Deep earthquakes associated with?

A

Subduction zones

45
Q

What are the 3 types of earhtquakes?

A
  • Normal Faulting
  • Transform Faulting
  • Deep Ocean Trench
46
Q

What occurs in Normal Faulting?

A

Two plates are pulled apart and tension forces cause them

47
Q

What occurs in Transform fualting?

A

Two plates are pulled apart strike slip forces cause the rocks to slide against each other

48
Q

What occurs in deep ocean trench earthquakes?

A

An oceanic plate slides under a continental plate

49
Q

What are the location of most earthquakes associated with?

A

Plate margins

50
Q

What do earthquakes that are not associated with plate margins assoicated with?

A

Old plate boundaries or Glaciation/Isostatic rebound

51
Q

What is Glaciation?

A

Ice that once pushed down on the earth’s surface but is now melting causing isostatic rebound as it comes back up

52
Q

What is Ground failure?

A

When the ground fails due to an earthquake

53
Q

What is Liquification?

A

When saturated soil is shaken which reduces the friction between soil particles that give the soil strength causing it to become like quicksand

EAS (33 decks)

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