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Geophysics (GOPH 355-UCAL) Midterm Exam I

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Question 1

An Earthquake generated a seismic wave. Initially the wave was propagating towards East. If the wave was to propagate in the opposite direction (towards West), which of the following statements would be true? (with respect to a particle)

A	The direction of the P-wave will changed 90-degrees to the original direction.
B	The direction of the S-wave will be changed 45-degrees to the original direction.
C	The direction of the P-wave will be changed to 45-degrees to the original direction.
D	The direction of the P-wave will remains the same.

Question 2

What angle is used in Snell's law?

A	The angle between the incident and reflected rays.
B	The angle between the ray and the normal to the surface.
C	The angle between the horizontal surface to the ray.
D	Half of the angle between the incident and reflected rays.

Question 3

In a refractive analysis, how many delay times sections (parts of the wave which a delay occur) would you expected to observe?

A	Only one, on the geophone side.
B	Two, on both at the seismic and geophone side.
C	One one, on the seismic source side.
D	Only one, between the refactor medium.

Question 4

Which of the following method will produce the highest degree of accuracy?

A	crossline
B	inline
C	1D

Question 5

Generally, modules are another name given for constants.

A	False
B	True

Question 6

A geophone is also know as...(more than one answer is possible)

A	receivers.
B	shot point.
C	source.
D	sensors.

Question 7

Sudden changes (jolts) in displacement is known as...

A	peaks.
B	spikes.
C	traces.
D	arrivals.

Question 7 Explanation: 

...or events

Question 8

By convention, when representing data depth is always increase upwards.

A	False
B	True

Question 9

Increase in density of a material will increase the speed of which the wave will propagate.

A	Flase
B	True

Question 9 Explanation: 

Since there is no room for free vibration due to tight packing of molecules in high density materials, the seismic waves travels faster.

Question 10

In Refracted Method, what angle of incident should you use for your analysis?

A	Rays with the incident ray at on or above the the critical angle.
B	Rays with the incident ray at exactly at the critical angle.
C	Rays with the incident ray below the critical angle.
D	Rays with the incident ray below the critical angle or 90-degrees to the normal.

Question 11

Why stress in one direction on an object, causes the material to change in all directions?

A	Because the atoms attract to each other, hence contacting in all other directions as a response to the stress.
B	Because the atoms repel to each other, hence contacting in all other directions as a response to the stress.
C	Because there is an infinite amount of matter.
D	Because there is a finite amount of matter.

Question 11 Explanation: 

The displacement in the direction of the stress is equal to the total displacement change in all other directions.

Question 12

What is the purpose of variable area plotting?

A	Qualitative analysis of data from several traces.
B	Quantitative analysis of data from traces of a single traces.
C	Quantitative analysis of data from several traces.
D	Qualitative analysis of data from traces of a single traces.

Question 13

Which of the following image represent a data gathered from a 3D seismic experiment?

Image Credit: Lecture notes, Dr. Kristopher Innanen

A	C
B	None of them.
C	A
D	B

Question 14

Why would you expect the wave equation to hold, even when the waves have to first travel across a medium before the distortion due to a density is detected by a geophone?

A	Because energy of the distortion cannot be created nor destroyed.
B	Because the distortion is a fixed variable once it passes through a low density medium.
C	Because the angle of which the distortion is preserved as the wave propagates through the medium.
D	Because the distortion propagates forward with time and more of less keep it's shape.

Question 15

"Every point on a wave-front may be considered a source of secondary spherical wavelets which spread out in the forward direction at the speed of light. The new wave-front is the tangential surface to all of these secondary wavelets." is the...

A	Fermat's principle
B	Newton's first law of waves
C	Huygens' principle
D	Snell's law

Question 16

Which can be used to interpret the Elastic behavior of rocks and sediments? (choose all that apply)

A	Poisson's ratio
B	Gravitational Law
C	Conservation of Energy Principle
D	Hooke's Law

Question 17

What law/principle have the following tenets:

The wave that starts at s and ends at g goes everywhere first.
But most of what is observed at g follows the path for which the travel time is a minimum.

A	Hook's law
B	Snell's law
C	Fermat's principle
D	Young's principle

Question 18

On the following figure, what colour of line represents the onset of refracted arrival?

Image Credit: Lecture notes, Dr. Kristopher Innanen

A	Yellow line
B	Blue line
C	Green line
D	Red line
E	Non-linear black line (bottom one)

Question 19

On which of the following situation(s) would you use the Refraction Method?

A	Figure I only
B	Figure J only
C	Figures I and J only
D	Figures I, J and K (all of them)
E	Figure K only

Question 19 Explanation: 

For Refraction Method(s), the incident ray enter the second medium at a critical angle and travels along the boundary. Then, it get refracted back on to the surface. All three diagrams above satisfy this principle.

Question 20

On the following figure, what is the x_cross value?

Image Credit: Lecture notes, Dr. Kristopher Innanen

A	0.7 seconds
B	1100 m
C	2900 m
D	3 seconds
E	2.3 seconds

Question 21

What profile view is shown here?

Image Credit: Lecture notes, Dr. Kristopher Innanen

A	Common Receiver Gather
B	Common Midpoint Gather
C	Common Offset Gather
D	Common Shot Gather

Question 22

In a typical experiment, which direction will have the most readings?

A	inline
B	into the plane
C	out of the plane
D	crossline

Question 23

If the velocity c is constant everywhere,then the relationship between distanced and time t is inversely proportional to each other.

A	False
B	True

Question 23 Explanation: 

d = c * t (directly proportional)

Question 24

What type of volume will highlight changes in geology only in x-direction and y-direction?

A	3D volumes
B	1D volumes
C	4D volumes
D	2D volumes

Question 25

What are the types of seismic sources? (choose ALL that apply)

A	Penetrated waves.
B	Refracted waves
C	Direct waves
D	Deflected waves.
E	Reflected waves

Question 26

What is the SI symbol for Young's modulus?

A	E
B	k
C	Y
D	μ

Question 27

If the following particle experiencing a seismic event, given the propagation direction (blue arrow), what arrow indicate the particle (green dot) motion of P wave?

A	All of the answers are wrong since P-wave only travels along the surface of the material (causing distortion)
B	Red arrow; along the y-axis (up and down)
C	Brown arrow; along the x-axis (left or/to right)
D	Perpendicular to the propagation direction

Question 28

Typically what type of direction is well sampled?

A	neither since they are interchangeable.
B	crossline geophones.
C	inline geophones.

Question 29

Every point on a wave-front may be considered a source of secondary spherical wavelets which spread out in the forward direction at the speed of light is known as...

A	Hook's law
B	Fermat's principle
C	Young's principle
D	Snell's law
E	Huygens' principle

Question 30

once a wave has entered a medium, it will propagate through the medium without deflection if and only if,

A	the medium changes it's volume over distance while maintaining a consent density.
B	the medium has an n value of exactly zero (0).
C	the medium is uniform all across.
D	the medium changes it's density over distance.

Question 31

How do the geophones work?

A	By measuring changes through voltage fluctuations.
B	By measuring changes through shock wave fluctuations.
C	By measuring changes through amp fluctuations.
D	By measuring changes through distance fluctuations.

Question 32

The degree of which an experiment can combat noise/interference is known as...

A	fold
B	in-line
C	stack
D	spread

Question 33

A source is also know as...(more than one answer is possible)

A	receiver
B	geophone
C	shot point
D	sensor

Question 34

Given the following information, what is the velocity of the third layer (L₃)?

Layer	CRMS (m/s)	2-way travel time (s)
1	2000	0.300
2	2115	0.380
3	2238	0.452

A	5607.42 m/s
B	74.89 m/s
C	2803.71 m/s
D	2799.01 m/s

Question 34 Explanation: 

Question 35

On the following diagram, the letter A (red letter) is highlighting what type of wave?

A	direct wave
B	transmitted wave
C	head wave
D	reflected wave

Question 36

Which side of the Displacement-Time graphs would you color?

A	Negative side
B	Negative and Positive side.
C	Positive side
D	Only when there is a major jolt

Question 37

The wave equation can be solved by a function of...

A	f(xt + c)
B	f(ct- x)
C	f(xt - c)
D	f(x - ct)
E	f(x - c/t)

Question 38

In the following equation, what is represented by x_g,y_g?

d = d(x_g,y_g,x_s,y_s|t)

A	The position of the geophone.
B	Depth which the ground reflection occurs.
C	The position of the ground refraction.
D	The position of the source.

Question 39

A ray travels through a medium of low density into a medium of high density. Assuming the ray passed into the high density layer, what would be the angle of refraction?

A	Would reach the critical number causing the ray to travel along the boundary between the two medium.
B	Decrease bending the ray towards the normal.
C	Deflect back up into the incident medium at about 180-degrees to the normal.
D	Increase bending the ray away from the normal.

Question 39 Explanation: 

Rays are faster in high density materials. Using Snell's law, you can prove that shorter the travel time (faster), higher the angle of of refraction.

Question 40

Inline ONLY experiments are considered to be 2D experiments.

A	False
B	True

Question 41

What is indicated by letter D (green line)?

A	Air blast
B	Direct arrival
C	Reflected arrival
D	Ground roll

Question 42

The wave propagated through air known as air blast. Where is the air blast in the following shot record?

A	at Y
B	at A
C	along D
D	along B
E	along C

Question 43

On the following diagram, the red letter B (red letter) is representing what type of wave?

A	reflected wave
B	direct wave
C	transmitted wave
D	head wave

Question 43 Explanation: 

Also known as refracted wave.

Question 44

What is indicated with W?

Image Credit: Lecture notes, Dr. Kristopher Innanen

A	The xonset
B	Plus-minus window
C	Beginning of the Direct arrival
D	Ground roll

Question 45

When dealing with variable area plotting, the data are recorded as displacement vs time. What is the correct formula for seismic displacement?

A	d = d(xm,ym,xs,ys|t)
B	d = d(xg,yg,xh,yh|t)
C	d = d(xs,ys,xg,yg|t)
D	d = d(xs,ys,xs,ys|t)
E	d = d(xg,yg,xs,ys|t)
F	d = d(xg,yg,xm,ym|t)

Question 46

Theoretically (practically also true), which type of wave is faster in a seismic event?

A	K-Waves
B	Sonic Waves
C	P-Waves
D	S-Waves

Question 47

On which of the following situation(s) would you use the plus-minus method?

A	I and J
B	None of them
C	J only
D	K only
E	I only

Question 48

On the following diagram, the letter D (red letter) is highlighting what type of wave?

A	reflected wave
B	transmitted wave
C	direct wave
D	head wave

Question 49

If the following particle experiencing a seismic event, given the propagation direction (blue arrow), what arrow indicate the particle (green dot) motion of S wave?

A	Red arrow; along the y-axis (up and down)
B	Brown arrow; along the x-axis (left or/to right)
C	All of the answers are wrong since S-wave only travels along the surface of the material (causing distortion)
D	Perpendicular to the propagation direction

Question 50

In seismic analysis, why do we use folds?

A	To reduce noise by increasing the CMP gather stacking.
B	To create events.
C	Folds are important geological events.
D	To increase the covered area.

Question 51

What will happen to a ray, when the incident angle of a ray is at the critical angle?

A	It will pass through the incident medium into the next medium along the normal.
B	It will bend towards the normal within the incident medium.
C	It will completely bend towards the incident medium. Hint: Not quite, but close.
D	It will move along the boundary between the two mediums while traveling in the incident medium.

Question 51 Explanation: 

Unless the incident angle is greater than that of critical angle, the ray will move along the boundary at exactly at critical angle.

Question 52

Pauli exclusion principle state that the atoms cannot occupy the same state.

A	False, because it is only applied to radioactive atoms.
B	True
C	False, because it is only applies to particles, not atoms.

Question 53

Given the n₁ = 2.4 (for layer 1), calculate the n₂, if a ray enters from L₁ into the L₂ at an angle of incidence 30-degrees and angle of refraction is 15-degrees.

A	4.64
B	13.66
C	1.93
D	2.44

Question 54

What part of the Distance Between Particles verses Potential Energy graph, the geophysicists are interested in?

A	The positive value of potential energy.
B	The non-elastic region.
C	The highest point of potential energy.
D	The lowest point of potential energy.

Question 55

Rays in a homogeneous medium are wavy lines.

A	True
B	False

Question 55 Explanation: 

They are straight lines. This is why we can use the Snell's law

Question 56

Which of the following image represent a data gathered from a 2D seismic experiment?

Image Credit: Lecture notes, Dr. Kristopher Innanen

A	B
B	A
C	C
D	None of them.

Question 57

Which of the following statements are attributed to Huygens–Fresnel principle?

A	The most of the waves observed at a point are the waves which travels the least amount of time.
B	The wave that starts at s and ends at g goes everywhere first.
C	The incident angle of a ray and the difference between the refractive indexes of each medium will govern the behavior of rays.
D	The wave front is created as a result of superposition of much smaller 2D or 3D wave fronts.

Question 58

To prove that wave equation is valid for all general problems, what key (while there may be more than one) mathematical principle should you use?

A	Trigonometry
B	Pythagoras theorem
C	Chain rule
D	Identity matrix

Question 59

On the following figure, what colour of line is used for representing refracted arrival?

Image Credit: Lecture notes, Dr. Kristopher Innanen

A	Non-linear black line (bottom one)
B	Yellow line
C	Red line
D	Blue line
E	Green line

Question 60

What profile view is shown here?

Image Credit: Lecture notes, Dr. Kristopher Innanen

A	Common Midpoint Gather
B	Common Offset Gather
C	Common Receiver Gather
D	Common Shot Gather

Question 61

Direct arrival is indicated with what?

A	along B
B	along C
C	along D
D	at A

Question 62

On the following diagram, the letter C (red letter) is highlighting what type of wave?

A	transmitted wave
B	reflected wave
C	direct wave
D	head wave

Question 63

What is a critical angle?

A	Angle of incident above which total reflection occurs.
B	Angle of incident below which total deflection occurs.
C	Angle difference between the incident ray and the reflected ray.
D	Angle of reflection below which total reflection occurs.
E	Angle of incident below which total reflection occurs.

Question 64

A ray travels through a medium of c₀ and enters into a medium of c₁. If the value of c₁ < c₀, the ray will bend ____.

A	downwards towards the normal decreasing in θ1
B	upwards towards the normal decreasing in θ1
C	downwards away from the normal increasing in θ1
D	downwards towards the normal increasing in θ1
E	upwards away from the normal increasing in θ1

Question 65

What is on the x-axis (red X)?

A	Depth in meters
B	Time in seconds
C	Distance in meters
D	Time in milliseconds

Question 66

What is the SI symbol for Bulk modulus?

A	k
B	E
C	U
D	μ

Question 67

What is NMO stand for and what does it provide?

A	Normal Mean Output, and it is the distance between the geophones in CMP gather.
B	Normal Move-out, and it is the distance between the source and the first geophone.
C	Normal Mean Output, and it is the difference between actual arrival time and the zero offset arrival time.
D	Normal Move-out, and it is the difference between actual arrival time and the zero offset arrival time.

Question 68

Delay time is the extra time needed for the wave to travel at at angle through a medium as opposed to traveling straight downwards.

A	False
B	True

Question 69

Given the following information, what is the velocity of the third layer (L₃)?

Layer	CRMS (m/s)	1-way travel time (s)
1	2050	0.192
2	2253	0.226
3	2590	0.312

A	2799.01 m/s
B	5604.95 m/s
C	3316.19 m/s
D	1099.71 m/s

Question 70

Where is the source position in the following shot record?

A	along C
B	along B
C	at A
D	along D
E	at Y
F	at X

Question 71

Traces are analyzed in sets known as groups.

A	False
B	True

Question 71 Explanation: 

Trace is analyzed in sets known as gathers.

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• What are the two tenets of them?
• How does it related to wave propagation?

– Different types of modules

• E, k, λ, etc
• What each of them represent?

– Snell’s Law

• What is a critical angle?
• What happen to a ray that enters into a medium at exactly at it’s critical angle?
• What is the behavior of a ray that would enter a medium that allow it to travel faster than the incident medium?
• What is the relation between the law and the seismic waves?

– What are the two types of seismic waves and how do their behaviors differ from each other?
– Can you do the proofs of all the formula used in class?
– Understanding shot records

• Be able to recognize a shot record
• Where is the ground roll, air blast, the source, direct arrival, reflected arrival?
• What is noise and most of which concentrated where on the shot record?
• What is recorded on x and y axises of a shot record?

– Several types of waves generated by a seismic source

• Head wave, direct wave, reflected wave, transmitted wave, etc
• How do they differ from each other?
• Which is relatively faster and what are the implications of it?
• Why do we care about different types of waves?

– What are the four types of gather?
– What is RMS, NMO and zero-offset?

Geophysics (GOPH 355-UCAL) Midterm Exam II

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Congratulations - you have completed Geophysics (GOPH 355-UCAL) Midterm Exam II.

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Question 1

Write the d(t) equation for the following wave. (ID-EXP2-20)

Image Credit: Topic samples, Dr. Kristopher Innanen

A	d(t) = cos (5t)
B	d(t) = sin (t)
C	d(t) = sin (5t)
D	d(t) = cos (t)

Question 2

According to the diagram, the T₂ (second layer) is __I__ and the T₃ is __II__. (ID-EXP2-12)

Image Credit: Topic samples, Dr. Kristopher Innanen

Layer / Z(m)	Cx (m/s)	Density Ρx (kg/m3)
L0 / Z1=200	2000	2200
L1 / Z2=350	2200	2100
L2 / Z3=500	2100	2200

A	I. 0.336 s II. 0.408 s
B	I. 0.479 s II. 0.408 s
C	I. 0.2 s II. 0.336 s
D	I. 0.336 s II. 0.479 s

Question 2 Explanation: 

Question 3

Broadcast Migration method is based on Huygens's Principle.

A	True
B	False

Question 4

When a current I passes through a rock, we would expect the resistivity r to be much higher than that of resistance R.

A	True
B	False

Question 5

What is the pseudo-depth given the velocity of 2000 m/s and the zero offset time of 0.5 seconds? (ID-EXP2-17)

A	1500 m
B	500 m
C	450 m
D	300 m

Question 5 Explanation: 

Z_p = (ct)/2

Question 6

Which of the following does not have any units?

A	permeability
B	amplitude
C	porosity
D	density

Question 7

If the impedance of the lower layer is __I__ than the impedance of the upper layer, the reflection coefficient will be __II__.

A	I. greater II. positive
B	I. smaller II. positive
C	I. smaller II. zero
D	I. greater II. negative

Question 8

What is the convolution of matrix of the following? (ID-EXP2-03)

a₁ = {2 , 3 , 2}
b₂ = {3 , 1}

A	{2, 9, 11, 6}
B	{2, 9, 6, 11}
C	{6, 11, 9, 2}
D	{11 ,6 9, 2}

Question 9

Which of the following matrix can satisfy the following? (ID-EXP2-06)

a₁ = {-1 , 4 , 2}
b₂ = {3 , 1}

A	-1 , 0 , 0 , 0 4 , -1 , 0 , 0 2 , 4 , -1 , 0 0 , 2 , 4 , 0 0 , 0 , 2 , 4 0 , 0 , 0 , 2
B	3 , 0 , 0 1 , 3 , 0 0 , 1 , 3 0 , 0 , 1
C	1 , 0 , 0 3 , 1 , 0 0 , 3 , 1 0 , 0 , 3
D	-1 , 0 , 0 , 0 4 , -1 , 0 , 0 2 , 4 , -1 , 0 0 , 0 , 4 , -1 0 , 0 , 2 , 4 0 , 0 , 0 , 2

Question 10

__I__ is used for nearby interfaces with same polarity and __I__ is used for nearby interfaces with opposite polarity.

A	I. Ricker II. Widess
B	I. Single wave II. opposing wave
C	I. Opposing wave II. single wave
D	I. Widess II. Ricker

Question 11

Frequency is given in Hz, which has units of seconds. (ID-EXP2-15)

A	True
B	False

Question 11 Explanation: 

The units are in inverse seconds. This is because f=1/T

Question 12

If the current amplitude values for the following defaults to 1, what is the corrected R value for the top (1st) spike? (ID-EXP2-14)

Image Credit: Topic samples, Dr. Kristopher Innanen

Layer / Z(m)	Cx (m/s)	Density Ρx (kg/m3)
L0 / Z1=200	2000	2200
L1 / Z2=350	2200	2100
L2 / Z3=500	2100	2200

A	0.0244
B	0.256
C	0.0951
D	0.16

Question 13

What is the acoustic impedance of the following layer? (ID-EXP2-10)

velocity = 2500 m/s
density = 2000 kg/m³

A	5,000,000
B	1.25
C	2,500,000
D	0.80

Question 13 Explanation: 

Z = v * ρ

Question 14

What is T₁ (first layer) on the following model? (ID-EXP2-11)

Image Credit: Topic samples, Dr. Kristopher Innanen

Layer / Z(m)	Cx (m/s)	Density Ρx (kg/m3)
L0 / Z1=200	2000	2200
L1 / Z2=350	2200	2100
L2 / Z3=500	2100	2200

A	0.2 s
B	0.1 s
C	440,000 ms
D	400,000 ms

Question 14 Explanation: 

T₁ = 2 (200 m/2000 m/s) = 0.2 s

Question 15

What is the size of the largest matrix multiplier for the following? (ID-EXP2-05)

a₁ = {1 , 5 , 2 , 4}
b₂ = {5 , 1 , 2}

A	3 x 3
B	6 x 6
C	6 x 5
D	4 x 4
E	4 x 6

Question 15 Explanation: 

{5 , 1 , 2} ==
5 , 0 , 0 , 0
1 , 5 , 0 , 0
2 , 1 , 5 , 0
0 , 2 , 1 , 5
0 , 0 , 2 , 1
0 , 0 , 0 , 2

Question 16

Given the frequency, 20 Hz, what is its basis vector? (ID-EXP2-16)

A	20 Hz
B	40 Hz
C	40pi rad/s
D	20pi rad/s

Question 16 Explanation: 

n = 2(pi)f

Question 17

Reflection experiments are better for targets at extreme depths. (ID-EXP2-01)

A	True
B	False

Question 18

The following image of a reflected event is most likely caused by a(an)... (ID-EXP2-26)

Image Credit: Topic samples, Dr. Kristopher Innanen

A	one steeply dipping interface.
B	anticline.
C	syncline.
D	two steeply dipping interfaces opposite to each other.

Question 19

The source wavelet can be best described with... (ID-EXP2-08)

A	b - second graph
B	highlighted regions on all three graphs
C	c - third graph
D	a - first graph

Question 20

Given; A dipping interface lies below a zero offset seismic survey. Below the midpoint location x_m = 50 m, the interface is at depth z₂=200m. Below the midpoint location x_m=300m, the interface is at depth z₃=250m. The seismic velocity above the interface is c₀. What is the dip angle?

A	39.5 degrees
B	50.1 degrees
C	75.9 degrees
D	11.3 degrees

Question 20 Explanation: 

Question 21

Given the following information, calculate the acoustic impedance. (ID-EXP2-09)

depth = 93600 m
time = 12 seconds
density = 2500 kg/m³

A	1.26 * 104
B	1.95 * 107
C	2.41 * 108
D	2.21 * 108

Question 21 Explanation: 

Z = v*p
Z = (93600/12 m/s)(2500 kg/m³)
Z = 19500000

Question 22

Given; A dipping interface lies below a zero offset seismic survey. Below the midpoint location x_m = 50 m, the interface is at depth z₂=200m. Below the midpoint location x_m=300m, the interface is at depth z₃=250m. The seismic velocity above the interface is c₀. What is the depth at z₁?

A	10.0 m
B	25.0 m
C	175 m
D	240.0 m

Question 23

What is convolution? (ID-EXP2-02)

A	Taking the logarithmic values of an experimental data to eliminate air blast.
B	A running average of an input t o produce a weighted output.
C	Changing the data to fit per-conditioned ideal set.
D	A running average of an output t o produce a weighted output.

Question 24

What is the frequency of this wave? (ID-EXP2-18)

Image Credit: Topic samples, Dr. Kristopher Innanen

A	0.2 Hz
B	1 Hz
C	0.5 Hz
D	5 Hz

Question 25

What is the convolution of matrix of the following? (ID-EXP2-04)

a₁ = {1 , 5 , 2 , 4}
b₂ = {5 , 1 , 2}

A	{17 , 32 , 26 , 5 , 8 , 8}
B	{17 , 5 , 26 , 32 , 8 , 8}
C	{5 , 17 , 32 , 26 , 8 , 8}
D	{5 , 26 , 17 , 32 , 8 , 8}

Question 26

What is the amplitude of this wave? (ID-EXP2-19)

Image Credit: Topic samples, Dr. Kristopher Innanen

A	4
B	3
C	5
D	1

Question 27

Which of the following is a representation of reflectivity series? (ID-EXP2-07)

A	c - third graph
B	highlighted regions on all three graphs
C	b - second graph
D	a - first graph

Question 28

What will be the pseudo-depth of a unit that was originally Z, but later the velocities was determined to be twice the original?

A	The depth will remain the same.
B	The corrected depth will be twice the original depth.
C	The corrected depth will be 1/3 of the original depth.
D	The corrected depth will be half the original depth.

Question 28 Explanation: 

Z = Ct / 2 ==> Z_new = 2Ct / 2

Question 29

According to the diagram, what is the thickness of layer 2? (ID-EXP2-13)

Image Credit: Topic samples, Dr. Kristopher Innanen

Layer / Z(m)	Cx (m/s)	Density Ρx (kg/m3)
L0 / Z1=200	2000	2200
L1 / Z2=350	2200	2100
L2 / Z3=500	2100	2200

A	150
B	50
C	Not enough info provided
D	100

Question 29 Explanation: 

500 m - 350 m = 150 m

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