Lecture 6: Earthquakes

Question 1

What is an earthquake?

Answer 1

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

Question 2

What is Elastic Rebound?

Answer 2

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

Question 3

What is a Slip?

Answer 3

The distance of the displacement between two rocks after an earthquake

Question 4

What are the 3 types of Faults?

Answer 4

• Normal Fault
• Thrusts/Reverse Fault
• Shearing/Strike-slip Forces

Question 5

What occurs in a Normal Fault?

Answer 5

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

Question 6

What occurs Thrust Faults?

Answer 6

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

Question 7

What occurs is Strike-slip faults?

Answer 7

Two plates slide past each other

Question 8

What are strike slip faults due to?

Answer 8

Shearing stress

Question 9

What are Normal faults due to?

Answer 9

Tensile Stress

Question 10

What are thrust faults due to?

Answer 10

Compressive stress

Question 11

What is the Focus?

Answer 11

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

Question 12

What is the Epicenter?

Answer 12

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

Question 13

What are Seismic waves?

Answer 13

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

Question 14

What are the 3 types of Seismic waves?

Answer 14

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

Question 15

What are P waves?

Answer 15

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

Question 16

In which medium do P waves travel faster in?

Answer 16

Solids

Question 17

What are S waves?

Answer 17

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

Question 18

In what medium do S waves travel in?

Answer 18

Solids only

Question 19

What are Surface waves?

Answer 19

Waves that are confined to the surface of the earth

Question 20

What are the two types of surface waves?

Answer 20

• Elliptical motion waves

* Sideways waves

Question 21

What occurs in Elliptical motion waves?

Answer 21

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

Question 22

What occurs in sidewats waves?

Answer 22

The ground shakes sideways with no vertical motion

Question 23

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

Answer 23

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

Question 24

Why are multiple seismograms from different location needed?

Answer 24

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

Question 25

How many km is the mantle?

Answer 25

40 kms

Question 26

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

Answer 26

* Crust * Mantle * Liquid Outer core * Solid Inner core

Question 27

What is the Radius of the earth?

Answer 27

6370 km

Question 28

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

Answer 28

20 km

Question 29

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

Answer 29

As you get denser the faster the waves will travel

Question 30

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

Answer 30

Both of their speeds drop because the Asthenosphere is partially molten

Question 31

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

Answer 31

They stop because S waves cannot travel through liquid

Question 32

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

Answer 32

The slow down because it is a less dense liquid

Question 33

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

Answer 33

They speed up because the mantle is more dense

Question 34

What causes the large S wave shadow?

Answer 34

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

Question 35

What causes the P wave shadow?

Answer 35

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

Question 36

What rock is oceanic crust made of?

Answer 36

Basalt

Question 37

What rock is Continental crust made of?

Answer 37

Granite

Question 38

What rock is the Mantel made out of?

Answer 38

Peridotite

Question 39

How thick can the crust get?

Answer 39

Up to 70km

Question 40

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

Answer 40

Granite

Question 41

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

Answer 41

Gabbro

Question 42

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

Answer 42

* 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

Question 43

What are Shallow earthquakes associated with?

Answer 43

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

Question 44

What are Deep earthquakes associated with?

Answer 44

Subduction zones

Question 45

What are the 3 types of earhtquakes?

Answer 45

* Normal Faulting * Transform Faulting * Deep Ocean Trench

Question 46

What occurs in Normal Faulting?

Answer 46

Two plates are pulled apart and tension forces cause them

Question 47

What occurs in Transform fualting?

Answer 47

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

Question 48

What occurs in deep ocean trench earthquakes?

Answer 48

An oceanic plate slides under a continental plate

Question 49

What are the location of most earthquakes associated with?

Answer 49

Plate margins

Question 50

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

Answer 50

Old plate boundaries or Glaciation/Isostatic rebound

Question 51

What is Glaciation?

Answer 51

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

Question 52

What is Ground failure?

Answer 52

When the ground fails due to an earthquake

Question 53

What is Liquification?

Answer 53

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