GATE - ALL WAVE VELOCITY RELATED QUESTIONS
GATE 2019
Q.17 A high frequency acoustic wave propagating in a gas saturated sandstone formation exhibits an increase in ________.
(A) frequency
(B) velocity
(C) wavelength
(D) wave number
GATE 2019
Q.25 The shear wave velocity in an igneous rock with a density of 2.7 gm/cc and rigidity modulus of 24.3 GPa is ______ km/s. (round off to 1 decimal place).
GATE 2019
Q.62 A 3-D seismic tomography experiment was carried out with an inter-station spacing of ‘X’ km. The subsurface velocity perturbations in three dimensional blocks were estimated with block size of ‘2X’km and ‘0.5X’km in case 1 and case 2, respectively. Which one of the following statements is CORRECT?
(A) The spatial resolution is poor and variance is small for case 1.
(B) The spatial resolution is good and variance is small for case 2.
(C) The spatial resolution is good and variance is large for case 1.
(D) The spatial resolution is poor and variance is large for case 2.
GATE 2019
Q.78 A split-spread reflection survey is carried out along a profile in the direction of the dipping interface. The difference in arrival times of the reflected waves from the interface at two geophones with an offset distance of 1000 m from the shot-point on both sides is 20 msec. If the velocity of the layer above the dipping interface is 3000 m/s, then the dip of the bed is ________degrees. (round off to 1 decimal place). (Assumption 2d >> X, where ‘d’ is depth below the shot-point normal to the interface and X is the source-geophone spacing)
GATE 2019
Q.80 In a seismogram of a shallow focus (h = 5 km) earthquake, the difference between the arrival times of the S and P phases is 1.34 s. Assuming the average P wave velocity of the crust to be 6.0 km/s and the Poisson’s ratio to be 0.27, the epicentral distance is _______kilometres. (round off to 1 decimal place)
GATE 2018
Q.24 Given that the velocity of P-waves in a sandstone matrix is 5600 m/s and that in oil is 1200 m/s, the velocity of P-wave propagation in oil saturated sandstone with 30% porosity is ___________ m/s. (Use Wyllie time average equation.)
GATE 2018
Q.69 Which one of the following well log responses characterizes an overpressured zone in the subsurface?
(A) High velocity and high resistivity.
(B) Low velocity and low density.
(C) High velocity and low resistivity.
(D) Low velocity and high density.
GATE 2018
Q.75 The P-wave velocity and the Poisson’s ratio for a homogeneous and isotropic sedimentary rock are 2500 m/s and 0.3, respectively. The S-wave velocity for the rock is ________m/s.
GATE 2018
Q.81 Consider a laterally homogeneous and isotropic earth model with a flat horizontal surface and three horizontal layers underlain by a half-space. A seismic reflection survey was simulated on this model with the sources and receivers placed on the surface. The table below lists the root mean square (rms) velocities, Vrms, and zero-offset two-way traveltimes t0 for the three reflection events from the bottom of each of the three layers observed in a pre-stack CDP (CMP) gather. The interval velocity of the second layer is _______ m/s.
GATE 2016
Q.27 A monochromatic elastic wave of frequency 20 Hz propagates in a medium with average velocity 3 km/s. For zero offset reflection from horizontal reflectors, the thickness of the vertical first Fresnel zone is ________ m.
GATE 2016
Q.28 The following figure shows a seismic reflection experiment above a reflector that dips 45°. The P-wave velocity in the medium is constant and equal to 2 km/s. The source is kept at location ‘S’ and the receiver is kept at location ‘G’. The midpoint between S and G is denoted by ‘M’ and the depth to the reflector from ‘M’ is 1 km. The traveltime of the primary reflected arrival recorded at the receiver is equal to____ seconds.
GATE 2015
Q.13 Gardner’s formula relates the seismic P-wave velocity (VP) to
(A) density
(C) permeability
(B) porosity
(D) lithology
GATE 2015
Q.46 In a 3-D seismic survey, the bin size for the maximum frequency (fmax) of 80 Hz at the target having a reflector dip of 150 and interval velocity of 3600 ms-1 is_______.
GATE 2015
Q.54 For the given near offset reflection geometry, the RMS velocity (in km/s) to the bottom of the second layer is ________.
GATE 2014
Q.3 From the surface to the Earth’s interior, the velocity of P-wave decreases and the material density increases at the boundary between
(A) Outer core and inner core
(B) Mantle and outer core
(C) Crust and mantle
(D) Upper crust and lower crust
GATE 2014
Q.24 The velocity discontinuity between the upper crust and the lower crust is known as ______________ discontinuity.
(A) Lehmann
(C) Mohorovičić
(B) Gütenberg
(D) Conrad
GATE 2014
Q.33 The S-wave velocity of a medium having a Poisson’s ratio and a P-wave velocity of 0.5 and 3 km/s respectively is _________km/s.
GATE 2013
Q.4 Amongst the following, which one will have the highest P-wave velocity?
(A) Granite
(B) Diamond
(C) Shale
(D) Talc
GATE 2013
Q.10 Acoustic impedance is the _____________ of density and velocity.
(A) sum
(B) difference
(C) product
(D) ratio
GATE 2013
Q.20 For seismic S-wave velocity, V, the rigidity modulus, µ, is proportional to
(A) SQ. ROOT OF V
(B) V
GATE 2013
Q.45 Wadati diagram is a plot of the difference in P- and S- wave arrival times against the arrival time of P-wave. It helps in estimating the
(A) velocity of P-wave.
(C) time of occurrence of earthquake.
(B) velocity of S-wave.
(D) hypocenter of earthquake.
GATE 2013
Q.55 The velocity of the EM wave (in km/s) is close to
(A) 20π
(B) 30 π
(C) 40 π
(D) 50 π
GATE 2012
Q.15 Which physical property of the medium governs the response of Ground Penetrating Radar (GPR)?
(A) Electrical conductivity
(C) Seismic wave velocity
(B) Electromagnetic conductivity
(D) Electrical permeability (dielectric permittivity)
GATE 2012
Q.27 A small scale seismic reflection survey was conducted with a shot point located at the middle of a 500 m long geophone spread. The NMO-corrected travel times at the end of the spread were found to be 1.227 s and 1.255 s. If the average seismic wave velocity above the reflector is 2500 m/s, what is the dip of the reflector? (Give the value in degrees in nearest integer)
(A) 4
(B) 6
(C) 8
(D) 10
GATE 2012
Q.28 The S-wave velocity in the lower continental crust is 6800 m/s and its density is 3380 kg/m3. Find its rigidity in GPa. (Give answer up to 2 decimal places)
(A) 156.29
(B) 160.21
(C) 162.34
(D) 164.11
GATE 2011
Q.3 The P-wave velocity of the earth’s mantle at the Mohoroviĉić discontinuity is
(A) 5.5 km/s
(B) 6.0 km/s
(C) 7.0 km/s
(D) 8.0 km/s
GATE 2011
Q.23 In a formation, if the density increases and elastic constants remain unchanged, then
(A) both P and S wave velocities increase
(B) P wave velocity increases and S wave velocity decreases
(C) both P and S wave velocities decrease
(D) P wave velocity decreases and S wave velocity increases
GATE 2011
Common Data for Questions 50 and 51
An asymmetric split spread extends from x1 = ?400 m to x2 = 800 m. A reflection observed on the spread yields t1 = 0.997 s at x1 = ?400 m, t2 = 1.025 s at x2 = 800 m, t0 = 1.0 s at x = 0.0 m and velocity of 2800 m/s.
Q.50 NMO correction estimated at x1 = ?400 m and x2 = 800 m are, respectively (A) 5 and 30 ms
(B) 8 and 35 ms (C) 10 and 41 ms (D) 15 and 45 ms
Q.51 The depth of the reflector at the shot point normal to the reflector is (A) 700 m
(B) 1400 m (C) 2100 m (D) 2800 m
Q.17 A high frequency acoustic wave propagating in a gas saturated sandstone formation exhibits an increase in ________.
(A) frequency
(B) velocity
(C) wavelength
(D) wave number
GATE 2019
Q.25 The shear wave velocity in an igneous rock with a density of 2.7 gm/cc and rigidity modulus of 24.3 GPa is ______ km/s. (round off to 1 decimal place).
GATE 2019
Q.62 A 3-D seismic tomography experiment was carried out with an inter-station spacing of ‘X’ km. The subsurface velocity perturbations in three dimensional blocks were estimated with block size of ‘2X’km and ‘0.5X’km in case 1 and case 2, respectively. Which one of the following statements is CORRECT?
(A) The spatial resolution is poor and variance is small for case 1.
(B) The spatial resolution is good and variance is small for case 2.
(C) The spatial resolution is good and variance is large for case 1.
(D) The spatial resolution is poor and variance is large for case 2.
GATE 2019
Q.78 A split-spread reflection survey is carried out along a profile in the direction of the dipping interface. The difference in arrival times of the reflected waves from the interface at two geophones with an offset distance of 1000 m from the shot-point on both sides is 20 msec. If the velocity of the layer above the dipping interface is 3000 m/s, then the dip of the bed is ________degrees. (round off to 1 decimal place). (Assumption 2d >> X, where ‘d’ is depth below the shot-point normal to the interface and X is the source-geophone spacing)
GATE 2019
Q.80 In a seismogram of a shallow focus (h = 5 km) earthquake, the difference between the arrival times of the S and P phases is 1.34 s. Assuming the average P wave velocity of the crust to be 6.0 km/s and the Poisson’s ratio to be 0.27, the epicentral distance is _______kilometres. (round off to 1 decimal place)
GATE 2018
Q.24 Given that the velocity of P-waves in a sandstone matrix is 5600 m/s and that in oil is 1200 m/s, the velocity of P-wave propagation in oil saturated sandstone with 30% porosity is ___________ m/s. (Use Wyllie time average equation.)
GATE 2018
Q.69 Which one of the following well log responses characterizes an overpressured zone in the subsurface?
(A) High velocity and high resistivity.
(B) Low velocity and low density.
(C) High velocity and low resistivity.
(D) Low velocity and high density.
GATE 2018
Q.75 The P-wave velocity and the Poisson’s ratio for a homogeneous and isotropic sedimentary rock are 2500 m/s and 0.3, respectively. The S-wave velocity for the rock is ________m/s.
GATE 2018
Q.81 Consider a laterally homogeneous and isotropic earth model with a flat horizontal surface and three horizontal layers underlain by a half-space. A seismic reflection survey was simulated on this model with the sources and receivers placed on the surface. The table below lists the root mean square (rms) velocities, Vrms, and zero-offset two-way traveltimes t0 for the three reflection events from the bottom of each of the three layers observed in a pre-stack CDP (CMP) gather. The interval velocity of the second layer is _______ m/s.
GATE 2016
Q.27 A monochromatic elastic wave of frequency 20 Hz propagates in a medium with average velocity 3 km/s. For zero offset reflection from horizontal reflectors, the thickness of the vertical first Fresnel zone is ________ m.
GATE 2016
Q.28 The following figure shows a seismic reflection experiment above a reflector that dips 45°. The P-wave velocity in the medium is constant and equal to 2 km/s. The source is kept at location ‘S’ and the receiver is kept at location ‘G’. The midpoint between S and G is denoted by ‘M’ and the depth to the reflector from ‘M’ is 1 km. The traveltime of the primary reflected arrival recorded at the receiver is equal to____ seconds.
GATE 2015
Q.13 Gardner’s formula relates the seismic P-wave velocity (VP) to
(A) density
(C) permeability
(B) porosity
(D) lithology
GATE 2015
Q.46 In a 3-D seismic survey, the bin size for the maximum frequency (fmax) of 80 Hz at the target having a reflector dip of 150 and interval velocity of 3600 ms-1 is_______.
GATE 2015
Q.54 For the given near offset reflection geometry, the RMS velocity (in km/s) to the bottom of the second layer is ________.
GATE 2014
Q.3 From the surface to the Earth’s interior, the velocity of P-wave decreases and the material density increases at the boundary between
(A) Outer core and inner core
(B) Mantle and outer core
(C) Crust and mantle
(D) Upper crust and lower crust
GATE 2014
Q.24 The velocity discontinuity between the upper crust and the lower crust is known as ______________ discontinuity.
(A) Lehmann
(C) Mohorovičić
(B) Gütenberg
(D) Conrad
GATE 2014
Q.33 The S-wave velocity of a medium having a Poisson’s ratio and a P-wave velocity of 0.5 and 3 km/s respectively is _________km/s.
GATE 2013
Q.4 Amongst the following, which one will have the highest P-wave velocity?
(A) Granite
(B) Diamond
(C) Shale
(D) Talc
GATE 2013
Q.10 Acoustic impedance is the _____________ of density and velocity.
(A) sum
(B) difference
(C) product
(D) ratio
GATE 2013
Q.20 For seismic S-wave velocity, V, the rigidity modulus, µ, is proportional to
(A) SQ. ROOT OF V
(B) V
(C) V^2
(D) V^3GATE 2013
Q.45 Wadati diagram is a plot of the difference in P- and S- wave arrival times against the arrival time of P-wave. It helps in estimating the
(A) velocity of P-wave.
(C) time of occurrence of earthquake.
(B) velocity of S-wave.
(D) hypocenter of earthquake.
GATE 2013
Q.55 The velocity of the EM wave (in km/s) is close to
(A) 20π
(B) 30 π
(C) 40 π
(D) 50 π
GATE 2012
Q.15 Which physical property of the medium governs the response of Ground Penetrating Radar (GPR)?
(A) Electrical conductivity
(C) Seismic wave velocity
(B) Electromagnetic conductivity
(D) Electrical permeability (dielectric permittivity)
GATE 2012
Q.27 A small scale seismic reflection survey was conducted with a shot point located at the middle of a 500 m long geophone spread. The NMO-corrected travel times at the end of the spread were found to be 1.227 s and 1.255 s. If the average seismic wave velocity above the reflector is 2500 m/s, what is the dip of the reflector? (Give the value in degrees in nearest integer)
(A) 4
(B) 6
(C) 8
(D) 10
GATE 2012
Q.28 The S-wave velocity in the lower continental crust is 6800 m/s and its density is 3380 kg/m3. Find its rigidity in GPa. (Give answer up to 2 decimal places)
(A) 156.29
(B) 160.21
(C) 162.34
(D) 164.11
GATE 2011
Q.3 The P-wave velocity of the earth’s mantle at the Mohoroviĉić discontinuity is
(A) 5.5 km/s
(B) 6.0 km/s
(C) 7.0 km/s
(D) 8.0 km/s
GATE 2011
Q.23 In a formation, if the density increases and elastic constants remain unchanged, then
(A) both P and S wave velocities increase
(B) P wave velocity increases and S wave velocity decreases
(C) both P and S wave velocities decrease
(D) P wave velocity decreases and S wave velocity increases
GATE 2011
Common Data for Questions 50 and 51
An asymmetric split spread extends from x1 = ?400 m to x2 = 800 m. A reflection observed on the spread yields t1 = 0.997 s at x1 = ?400 m, t2 = 1.025 s at x2 = 800 m, t0 = 1.0 s at x = 0.0 m and velocity of 2800 m/s.
Q.50 NMO correction estimated at x1 = ?400 m and x2 = 800 m are, respectively (A) 5 and 30 ms
(B) 8 and 35 ms (C) 10 and 41 ms (D) 15 and 45 ms
Q.51 The depth of the reflector at the shot point normal to the reflector is (A) 700 m
(B) 1400 m (C) 2100 m (D) 2800 m
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