NOUN TMA Solutions: phy361 - Geophysics II

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NOUN TMA Solutions: phy361 - Geophysics II

Postby Jed » Mon Jul 16, 2018 9:55 am

NOUN TMA Solutions: phy361 - Geophysics II


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Q21 A line of geophones laid out for a refraction survey is known as

spread

Q22 the distance from the shoirt point at which energy arrives after refkection at the critical angle is caled

critical distance

Q23 the critical time is obtained by

dividing the critical distance by the wave velocity

Q24 the critical distance for which the travke times of the direct and refracted waves are proportional to

interface dep th

Q25 when thr refracted ray travel paralled to the interface at the velocity of the second layer

critical refraction occurs

Q26 in a deep reflection survey how do you increase the signak-to-noise ratio

by stacking

Q27 the range of frequencies over which attenciation of the direct wave occurs is proportional to

array length

Q28 which of the following arrays produce the most complex curves

non-linear arr ays

Q29 the efficiency with which a wave is atteniable by an array is defined by its

relative effect

Q30 the distance from the short point to the furthest geophone is called

spread lengt h

Q31 which of the following is not a type of multiple reflection

inter-formational multiple
Q32 which of the following is the most reliable way of dstinguishing shallow reflection from refractions

curvature

Q33 the normal incidence time is given by

2d/v

Q34 As the angle of incidence increase in reflection survey the amount of energy reflected first

decreases and then increases

Q35 the equation RC (I1-I2)/(I2+I1) is called

reflection coefficiant

Q36 Acoustic impedance of a rock is equal to the product of its density and the

velocity of P-wave

Q37 which of the following describes a raleigh wave

it travel only along the free surface of a solid mater ial

Q38 when shear deformation propagates in an elastic solid, the motion of individual particules is always

perpendicular to the direction of wave

Q39 Body waves consist of the

P and S wave Only

Q40 If a P-wave were to go from a solid to a liquid, what woud happen to its velocity?

increase



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Jed
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Re: NOUN TMA Solutions: phy361 - Geophysics II

Postby Jed » Mon Jul 16, 2018 9:56 am

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Q1 if velocity decreases at an interface ________ cannot occur

critical refracti on

Q2 A refractor that dos not give rise to any first arrival is said to be ________

hiddeen

Q3 the ________ consists of P- and body waves, love and rayleigh surface waves

ground roll

Q4 the sciences of seisomology dates from the invention of the seisomograph by ________ in 1892

John milne

Q5 in reflection survey if there is only one single interface, the depth of the refractor beneath the geophone is equal to the ______ of the upper layer

thicknes s

Q6 reciprocal time is the time taken for seismic energy to travel between the ________ position

two long – shot

Q7 where a refractor ha a ______ the slop of the difference line will be equal to the dip velocity equation

constant dip

Q8 most refractors except the _____ are irregular

water table

Q9 if shots are fired from both ends of the spread different apparent velocities will be measured because the sign of the ______ angle will differ

dip

Q10 ___________is defied as the time at which the back-extrapolated refracted arrival line cuts the time axies

intercept time

Q11 seismic velocities _________ are often greater than in surrounding formations

salt and evaporates

Q12 refraction method is particularly suitable where the structure of a __________ surface is the target of geological interest

high speed

Q13 the refraction method provides data on the __________ of the refracting beds

velocity

Q14 in reflection surveying, the seismic waves must travel large ___________ distances through the earth

horizontal

Q15 in reflection surveying, the detection instruments detect seismic signals at a distance from the ____________ that is large compared with the depth of the horizon to be mpped

shot point

Q16 _______ corresponds to slow velocities

sleep slopes

Q17 on a time distance plot, the gradient of any line is equal to the _________

reciprocal of the velocity

Q18 Picking _______ on refraction record relies on subjective estimates of first break positions.

first waves

Q19 centre shots are very useful if there are considerable difference in interpretation at _________

opposite ends of the spread

Q20 in most refraction surveys_______ are fired very close to the ends of the spread

shorts shots





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Jed
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Re: NOUN TMA Solutions: phy361 - Geophysics II

Postby Jed » Mon Jul 16, 2018 9:58 am

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Q41 If a P-wave were to go from a solid to a liquid, what woud happen to its velocity?

increase

Q42 If only density increase with increasing depth within the earth the velocity of a P-wave should

decrease

Q43 which of the following sequences correctly list the different arrivals from first to last?

P-waves, swaves and surface waves

Q44 the velocity of seismic waves varies through the earth because

density of rocks varies within the e arth

Q45 what is a dynamic range?

the range over which data can be recorded with roughly u niform percentage accuracies.

Q46 which of the following is not a seismic equipment

land

Q47 what do you do to reduce both high frequency random noise and long period noise

apply filters

Q48 in single chammer seismograph, noise level can be monitored by

observing the trace in the absence of a source puls e

Q49 Seismographs are instrument that

record seismic signal

Q50 noise which is not generated by the shot is called

random noise

Q51 which of the following is referred to as seismometers

geophones

Q52 which of the following waves are usually regarded as noise

S-wave

Q53 Both geophones and hydrophones convert

mechanical energy to electrical signals

Q54 land seismic detectors are called

geophones

Q55 the time at which the seismic wave is initated in a seismic survey which appears on the record as a break is known as

Time break

Q56 which of the following is not a safety precaution when using explosives as seismic sources?

the shot-firer should not be far away from the shot-p oint

Q57 which of the following is not a common seismic source?

heavy stone

Q58 Porosity in rocks is normally increase by

size

Q59 snell's law is mathematically express by which of th wollowing equation?

$$ sin i/sin r =V _{1}/V_{2}$$

Q60 which of the following is a limitation of seismic refraction survey

it cannot detected a lower velocity layer beneath a higher velocity layer




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Jed
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Re: NOUN TMA Solutions: phy361 - Geophysics II

Postby Jed » Mon Jul 16, 2018 10:02 am

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Q81 the depth of penetration in seismic refraction survey is approximately

1/5th of the length of the geophone spread

Q82 which of the following is not a common application of seismic refraction method?

measuring electrical conductivitiy of earth materials with depth.

Q83 hydrophones are insturment used for detecting seismic wave in

in water

Q84 A Seismic wave can be said to be

an acoustic energy

Q85 during seismic refraction survey, the geophone detects seismicsignals at what distance?

distance from the shot point

Q86 modern electromagnetic instruments are constructed so as to record simultaneously ______ components of motion.

three orthogonal

Q87 which of the following rock has high velocity but low density?

salt

Q88 Rock Velocity is reduced by which of the following

Porosity

Q89 which of the following is a characteristics of dry rocks

very low p-wave ve locities

Q90 Which of the following law governms refraction?

Snell's Law

Q91 during refraction which of the following is not refracted

normal induc e ray

Q92 Which of the following is true about the law of reflection?

incident angle and reflect5ion angle are equal

Q93 In the law of universal gravitation, which of the following is true?

the product of the masses is inversely propotional to the sqwuare of their distance apa rt

Q94 With reflection methods, one can locate and map which of the following features?

anticlines and salt domes

Q95 Which of the following is used for recording wave signals?

seismograph

Q96 Which of the following is used for wave detection?

geophone

Q97 In seismic reflection method, the reflection are recorded by detecting instruments responsive to

groun d motion

Q98 Which of the following methiods is the most prefered methodfor oil exploration?

seismic reflection

Q99 Ther main insterument used in seismic survey is

seismograo h

Q100 In seismic prospecting the structure of subsurface formation is mapped by measuring what?

the arrival times andf velo 0city of the ptrimary wave




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Jed
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Re: NOUN TMA Solutions: phy361 - Geophysics II

Postby Jed » Mon Jul 16, 2018 10:03 am

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Q61 the depth of penetration in seismic refraction survey is approximately

1/5th of the length of the geophone spread

Q62 which of the following is not a common application of seismic refraction method?

measuring electrical conductivitiy of earth materials with depth.

Q63 hydrophones are insturment used for detecting seismic wave in

in water


Q64 A Seismic wave can be said to be

an acoustic energy

Q65 during seismic refraction survey, the geophone detects seismicsignals at what distance?

distance from the shot point

Q66 modern electromagnetic instruments are constructed so as to record simultaneously
components of motion.

three orthogonal

Q67 which of the following rock has high velocity but low density?

salt

Q68 Rock Velocity is reduced by which of the following

Porosity

Q69 which of the following is a characteristics of dry rocks

very low p-wave ve locities

Q70 Which of the following law governms refraction?

Snell's Law

Q71 during refraction which of the following is not refracted

normal induc e ray

Q72 Which of the following is true about the law of reflection?

incident angle and reflect5ion angle are equal

Q73 In the law of universal gravitation, which of the following is true?

the product of the masses is inversely propotional to the sqwuare of their distance apa rt

Q74 With reflection methods, one can locate and map which of the following features?

anticlines and salt domes

Q75 Which of the following is used for recording wave signals?

seismograph

Q76 Which of the following is used for wave detection?

geophone

Q77 In seismic reflection method, the reflection are recorded by detecting instruments responsive to

groun d motion

Q78 Which of the following methiods is the most prefered methodfor oil exploration?

seismic reflection

Q79 Ther main insterument used in seismic survey is

seismograo h

Q80 In seismic prospecting the structure of subsurface formation is mapped by measuring what?

the arrival times andf velo 0city of the ptrimary wave






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