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Geophysics (GOPH 355-UCAL) Midterm Exam I

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Question 1

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	Perpendicular to the propagation direction
C	Brown arrow; along the x-axis (left or/to right)
D	Red arrow; along the y-axis (up and down)

Question 2

In seismic analysis, why do we use folds?

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

Question 3

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

Question 4

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

Question 4 Explanation: 

Question 5

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

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

Question 6

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

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

Question 7

How do the geophones work?

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

Question 8

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	13.66
B	1.93
C	2.44
D	4.64

Question 9

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	Increase bending the ray away from the normal.
C	Deflect back up into the incident medium at about 180-degrees to the normal.
D	Decrease bending the ray towards the normal.

Question 9 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 10

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

Question 11

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

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

Question 12

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

Image Credit: Lecture notes, Dr. Kristopher Innanen

A	C
B	B
C	A
D	None of them.

Question 13

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 distortion propagates forward with time and more of less keep it's shape.
D	Because the angle of which the distortion is preserved as the wave propagates through the medium.

Question 14

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

A	True
B	Flase

Question 14 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 15

Traces are analyzed in sets known as groups.

A	True
B	False

Question 15 Explanation: 

Trace is analyzed in sets known as gathers.

Question 16

Where is the source position in the following shot record?

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

Question 17

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

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

Question 18

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

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

Question 19

What is the purpose of variable area plotting?

A	Qualitative analysis of data from traces of a single 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 several traces.

Question 20

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

Image Credit: Lecture notes, Dr. Kristopher Innanen

A	B
B	A
C	None of them.
D	C

Question 21

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

A	False
B	True

Question 22

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

Image Credit: Lecture notes, Dr. Kristopher Innanen

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

Question 23

What angle is used in Snell's law?

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

Question 24

Generally, modules are another name given for constants.

A	True
B	False

Question 25

What is indicated by letter D (green line)?

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

Question 26

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

Image Credit: Lecture notes, Dr. Kristopher Innanen

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

Question 27

What profile view is shown here?

Image Credit: Lecture notes, Dr. Kristopher Innanen

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

Question 28

What is indicated with W?

Image Credit: Lecture notes, Dr. Kristopher Innanen

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

Question 29

Typically what type of direction is well sampled?

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

Question 30

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

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

Question 31

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

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

Question 32

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

Question 33

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

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

Question 34

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

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

Question 35

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

Question 36

What is the SI symbol for Bulk modulus?

A	μ
B	k
C	U
D	E

Question 37

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 38

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

Question 39

On the following figure, what is the x_cross value?

Image Credit: Lecture notes, Dr. Kristopher Innanen

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

Question 40

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

Question 41

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

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

Question 42

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

A	True
B	False

Question 42 Explanation: 

d = c * t (directly proportional)

Question 43

What is NMO stand for and what does it provide?

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

Question 44

Direct arrival is indicated with what?

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

Question 45

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

Question 46

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

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

Question 46 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 47

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 48

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	Chain rule
C	Identity matrix
D	Pythagoras theorem

Question 49

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

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

Question 50

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

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

Question 50 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 51

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 51 Explanation: 

Also known as refracted wave.

Question 52

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

A	1D
B	crossline
C	inline

Question 53

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

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

Question 53 Explanation: 

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

Question 54

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	True
B	False

Question 55

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

A	fold
B	stack
C	spread
D	in-line

Question 56

What is a critical angle?

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

Question 57

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

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

Question 58

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

Question 59

Rays in a homogeneous medium are wavy lines.

A	False
B	True

Question 59 Explanation: 

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

Question 60

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

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

Question 61

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

Question 62

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

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

Question 63

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

A	geophone
B	receiver
C	shot point
D	sensor

Question 64

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

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

Question 65

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

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

Question 66

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

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

Question 67

Inline ONLY experiments are considered to be 2D experiments.

A	False
B	True

Question 68

What is the SI symbol for Young's modulus?

A	μ
B	Y
C	k
D	E

Question 69

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

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

Question 69 Explanation: 

...or events

Question 70

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

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

Question 71

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

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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

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

Question 1 Explanation: 

Question 2

Which of the following does not have any units?

A	amplitude
B	porosity
C	permeability
D	density

Question 3

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	25.0 m
B	240.0 m
C	10.0 m
D	175 m

Question 4

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	Not enough info provided
C	100
D	50

Question 4 Explanation: 

500 m - 350 m = 150 m

Question 5

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

Image Credit: Topic samples, Dr. Kristopher Innanen

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

Question 6

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	A running average of an output t o produce a weighted output.
D	Changing the data to fit per-conditioned ideal set.

Question 7

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

A	True
B	False

Question 8

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

Question 9

Broadcast Migration method is based on Huygens's Principle.

A	False
B	True

Question 10

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

a₁ = {2 , 3 , 2}
b₂ = {3 , 1}

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

Question 11

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

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

Question 12

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	75.9 degrees
B	39.5 degrees
C	50.1 degrees
D	11.3 degrees

Question 12 Explanation: 

Question 13

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

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

Question 13 Explanation: 

n = 2(pi)f

Question 14

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	0.256
B	0.0244
C	0.0951
D	0.16

Question 15

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 16

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

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

Question 17

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

Question 18

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

A	True
B	False

Question 18 Explanation: 

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

Question 19

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

Image Credit: Topic samples, Dr. Kristopher Innanen

A	4
B	5
C	1
D	3

Question 20

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

Question 20 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 21

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	300 m
B	500 m
C	1500 m
D	450 m

Question 21 Explanation: 

Z_p = (ct)/2

Question 22

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

Image Credit: Topic samples, Dr. Kristopher Innanen

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

Question 23

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 half the original depth.
D	The corrected depth will be 1/3 of the original depth.

Question 23 Explanation: 

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

Question 24

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

a₁ = {-1 , 4 , 2}
b₂ = {3 , 1}

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

Question 25

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

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

Question 26

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

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

Question 27

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

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

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

Question 27 Explanation: 

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

Question 28

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

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

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

Question 28 Explanation: 

Z = v * ρ

Question 29

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

Question 29 Explanation: 

T₁ = 2 (200 m/2000 m/s) = 0.2 s

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