GATE- ALL GRAVITY RELATED QUESTIONS
GATE 2019
Q.5 The acceleration due to gravity (g) begins to fall sharply towards the centre of the Earth from the ________ discontinuity.
(A) Conrad (B) Mohorovicic (C) Gutenberg (D) Lehmann
GATE 2019
Q.15 Which one of the following is only a correction and not a reduction in the computation of gravity anomalies with respect to a datum?
(A) Free air (B) Bouguer (C) Terrain (D) Isostatic
GATE 2019
Q.71 In gravity anomalies, the ‘Indirect effect’ mainly arises from ________.
(A) the sources outside the area of investigation
(B) improper instrument drift
C) effect of mass lying between the geoid and ellipsoid
(D) short-wavelength uncompensated masses in the subsurface
GATE 2019
Q.74 If ΔJ and Δσ are the uniform magnetization and density contrasts respectively, of a point source, the relation between the vertical components of the gravity (gz) and magnetic (Tz) anomalies can be expressed (neglecting long-wavelength component) as _________. (G is Gravitational constant)
GATE 2019
Q.75 Which one of the following statements about the gravity anomalies on land is CORRECT?
(A) Free-air and Bouguer anomalies are always positively correlated with elevation
(B) Isostatic anomalies are not useful to understand the crustal heterogeneities
(C) Vertical derivatives are used to enhance the gravity effects of deep-seated bodies
(D) X-horizontal gradient (Delta g/ Delta x)map enhances / sharpens anomalies of bodies trending N-S (X-East, Y-North, Z-downward).
GATE 2019
Q.77 In an abandoned mine-site, three hollow spherical cavities are located below the surface centered at depths of 50, 100 and 150 metres. Assuming that residual gravity is low due to each one of these cavities are small (~ 0.05 mGal), do not interfere and can be detected by the gravimeter, the most ideal (largest) grid spacing for carrying out the gravity surveys in order to correctly delineate these cavities is _________metres. (round off to the nearest integer).
GATE 2018
Q.6 Which one of the following geophysical methods uses the physical property ‘Dielectric Constant’?
(A) Gravity
(C) Seismic
(B) Ground Penetrating Radar
(D) Self-Potential
GATE 2018
Q.15 The geoid can be best defined as
(A) an oblate spheroid that best approximates the shape of the earth.
(B) a surface over which the value of gravity is constant.
(C) the physical surface of the earth.
(D) an equipotential surface of gravity of the earth.
GATE 2018
Q.21 Which one of the following corrections is always added during reduction of the observed gravity data?
(A) Latitude (B) Free-air (C) Bouguer (D) Terrain
GATE 2018
Q.50 The mass and volume of a natural soil sample are 2.1 kg and 1×10-3 m3, respectively. When fully dried, the mass of the soil sample becomes 2 kg without any change in volume. Assuming the specific gravity of soil particles to be 2.5, and water density of 1000 kg/m3, the degree of saturation of the natural soil sample is _______________%.
GATE 2018
Q.72 In the figure below, Z denotes the depth to the center of a buried sphere from the surface and X1/2 denotes the half-width of the profile at half the maximum value of gravity. Then, the ratio Z/X1/2 is ________.
GATE 2018
Q.73 Two survey vessels with shipborne gravimeters are cruising towards each other at a speed of 6 knots each along an east-west course. The difference in gravity readings of the two gravimeters is 63.5 mGal at the point at which the survey vessels cross each other. The latitude along which the survey vessels are cruising is ______N.
GATE 2018
Q.74 A gravity reading is taken in a stationary helicopter hovering 1 km above mean-sea level at a particular location. The difference in the value of g measured in the helicopter and at mean sea level vertically beneath the helicopter is ____________ mGals.
GATE 2016
Q.7
According to Airy’s model, gravity anomalies for fully isostatically compensated topography are characterized by
(A) negative Bouguer anomaly and positive free-air anomaly.
(B) positive Bouguer anomaly and negative free-air anomaly.
(C) zero Bouguer anomaly and negative free-air anomaly.
(D) positive Bouguer anomaly and zero free-air anomaly.
GATE 2016
Q.18 Which one of the following geophysical methods is most suitable for the exploration of a horizontally stratified graphite deposit at a depth of 50 m?
(A) Gravity (B) Magnetic (C) Radiometric (D) Electromagnetic
GATE 2016
Q.32 The value of free-air correction (assuming sea level as datum plane) at an elevation of 150 m is _________ mGal.
GATE 2016
Q.33 A spherical cavity of radius 8 m has its centre 15 m below the surface. If the cavity is full of sediments of density 1.5?103 kg/m3 and is in a rock body of density 2.4?103 kg/m3, the maximum value of its gravity anomaly is __________ mGa
GATE 2016
Q.34 Match the items (listed in Group I) with the corresponding corrections applied for reduction of marine gravity data (listed in Group II).
Group I
P. Effect of rotating homogeneous ellipsoidal Earth
Q. Effect of deficit mass from mean sea level to average depth
R. Effect of relative motion of ship with respect to revolving Earth
S. Effect of elastic creep of gravimeter spring system and Earth tides
Group II
1.Drift correction
2. Latitude correction to ocean floor
3. Bouguer correction
4. Eotvos correction
(A) P-4; Q-3; R-1; S-2
(B) P-2; Q-3; R-4; S-1
(C) P-4; Q-1; R-2; S-3
(D) P-3; Q-1; R-4; S-2
GATE 2015
Q.45 The Bouguer anomaly obtained after applying all necessary corrections is due to
(A) topographic undulations above the datum
(B) increase in densities of crustal rocks with depth
(C) lateral density variations
(D) vertical density contrast across Moho
GATE 2015
Q.47 A spherical body with its centre located at a depth of 1040 m gives a symmetric residual gravity anomaly high with Δgmax = 5.2 mGal. If the same anomaly were to be obtained over a 2-D horizontal cylinder, the depth to the centre of the horizontal cylinder (in m) is_______.
GATE 2014
Q.10 The International Gravity Formula predicts the theoretical gravity value at a given point assuming a
(A) non-rotating homogeneous spherical earth model
(B) rotating inhomogeneous spherical earth model
(C) rotating homogeneous oblate spheroidal earth model
(D) rotating inhomogeneous oblate spheroidal earth model
GATE 2014
Q.37 The Poisson’s relation linking the gravity and magnetic potentials assumes the same anomaly source with
(A) inhomogeneous density and intensity of magnetization
(B) uniform density contrast and inhomogeneous intensity of magnetization
(C) uniform density contrast and homogeneous intensity of magnetization
(D) inhomogeneous density and homogeneous intensity of magnetization
GATE 2014
Q.52 Compute the maximum value of gravity anomaly in µGal over a buried sphere from the following data:
Radius of a sphere = 5 m
Density contrast = 0.1 gm/cc
Depth to centre of sphere =11 m
G = 6.673x10-8 dyne-cm2/gm2
(A) 2887.58
(B) 288.76
(C) 28.88
(D) 2.89
GATE 2013
Q.37 If L, B, F and T respectively stand for Latitude correction, Bouguer correction, Free-air correction and Terrain correction, then the order in which they will have to be applied for gravity data analysis is
(A) LFBT (B) LBTF (C) FLBT (D) TBLF
GATE 2013
Q.40 Which of the following is useful to estimate the depth to the centre of a spherical body from a gravity anomaly curve?
(A) Surface integration
(B) Volume integration
(C) Twice the absolute maximum
(D) Half-width of the anomaly
GATE 2012
Q.9 Bouguer correction is applied to correct for the gravity anomaly due to mass between station location and
(A) mean sea level (C) base of upper crust (B) local datum plane (D) Mohorovicic discontinuity
GATE 2012
Q.36 The change in gravity caused by Earth’s tides on the land surface in a complete tidal cycle is in the range of (in milligal)
(A) 0.1 to 0.2
(C) 0.3 to 0.4
(B) 0.2 to 0.3
(D) 0.4 to 0.5
GATE 2011
Q.21
The acceleration due to gravity (g) and universal gravitational constant (G) are related by the expression (Me and Re are the mass and radius of the earth, respectively)
GATE 2011
Q.34
Gravity measurement is made on a ship sailing at the speed of 6 knots in the direction N65?E at 20?N latitude. The Eotvos correction (in mGal) is
(A) +38.5 (B) +24.5 (C) -35.5(D) -39.5.
GATE 2011
Q.35 Isostatic residual anomaly over a mountainous terrain is due to (D) ?39.5
(A) gravitational effect of compensating mass
(B) long wavelength variations of topography
(C) short wavelength variations of topography
(D) density inhomogeneities in the upper and middle crust
GATE 2011
Statement for Linked Answer Questions 52 and 53:
A gravity survey is conducted over a highly compact ore deposit (spherical shape). Bouguer anomaly values reduced along a profile are given below.
Q.52 What is the depth to the center of the ore deposit?
(A) 3100 m
(B) 1820 m
(C) 1560 m
(D) 1450 m
Q.53 What is the excess mass (in metric tons) by the deposit?
(A) 1.615 X 10^8
(B) 2.165 X 10^8
(C) 1.312 X 10^9
(D) 1.825 X 10^9
Q.5 The acceleration due to gravity (g) begins to fall sharply towards the centre of the Earth from the ________ discontinuity.
(A) Conrad (B) Mohorovicic (C) Gutenberg (D) Lehmann
GATE 2019
Q.15 Which one of the following is only a correction and not a reduction in the computation of gravity anomalies with respect to a datum?
(A) Free air (B) Bouguer (C) Terrain (D) Isostatic
GATE 2019
Q.71 In gravity anomalies, the ‘Indirect effect’ mainly arises from ________.
(A) the sources outside the area of investigation
(B) improper instrument drift
C) effect of mass lying between the geoid and ellipsoid
(D) short-wavelength uncompensated masses in the subsurface
GATE 2019
Q.74 If ΔJ and Δσ are the uniform magnetization and density contrasts respectively, of a point source, the relation between the vertical components of the gravity (gz) and magnetic (Tz) anomalies can be expressed (neglecting long-wavelength component) as _________. (G is Gravitational constant)
GATE 2019
Q.75 Which one of the following statements about the gravity anomalies on land is CORRECT?
(A) Free-air and Bouguer anomalies are always positively correlated with elevation
(B) Isostatic anomalies are not useful to understand the crustal heterogeneities
(C) Vertical derivatives are used to enhance the gravity effects of deep-seated bodies
(D) X-horizontal gradient (Delta g/ Delta x)map enhances / sharpens anomalies of bodies trending N-S (X-East, Y-North, Z-downward).
GATE 2019
Q.77 In an abandoned mine-site, three hollow spherical cavities are located below the surface centered at depths of 50, 100 and 150 metres. Assuming that residual gravity is low due to each one of these cavities are small (~ 0.05 mGal), do not interfere and can be detected by the gravimeter, the most ideal (largest) grid spacing for carrying out the gravity surveys in order to correctly delineate these cavities is _________metres. (round off to the nearest integer).
GATE 2018
Q.6 Which one of the following geophysical methods uses the physical property ‘Dielectric Constant’?
(A) Gravity
(C) Seismic
(B) Ground Penetrating Radar
(D) Self-Potential
GATE 2018
Q.15 The geoid can be best defined as
(A) an oblate spheroid that best approximates the shape of the earth.
(B) a surface over which the value of gravity is constant.
(C) the physical surface of the earth.
(D) an equipotential surface of gravity of the earth.
GATE 2018
Q.21 Which one of the following corrections is always added during reduction of the observed gravity data?
(A) Latitude (B) Free-air (C) Bouguer (D) Terrain
GATE 2018
Q.50 The mass and volume of a natural soil sample are 2.1 kg and 1×10-3 m3, respectively. When fully dried, the mass of the soil sample becomes 2 kg without any change in volume. Assuming the specific gravity of soil particles to be 2.5, and water density of 1000 kg/m3, the degree of saturation of the natural soil sample is _______________%.
GATE 2018
Q.72 In the figure below, Z denotes the depth to the center of a buried sphere from the surface and X1/2 denotes the half-width of the profile at half the maximum value of gravity. Then, the ratio Z/X1/2 is ________.
GATE 2018
Q.73 Two survey vessels with shipborne gravimeters are cruising towards each other at a speed of 6 knots each along an east-west course. The difference in gravity readings of the two gravimeters is 63.5 mGal at the point at which the survey vessels cross each other. The latitude along which the survey vessels are cruising is ______N.
GATE 2018
Q.74 A gravity reading is taken in a stationary helicopter hovering 1 km above mean-sea level at a particular location. The difference in the value of g measured in the helicopter and at mean sea level vertically beneath the helicopter is ____________ mGals.
GATE 2016
Q.7
According to Airy’s model, gravity anomalies for fully isostatically compensated topography are characterized by
(A) negative Bouguer anomaly and positive free-air anomaly.
(B) positive Bouguer anomaly and negative free-air anomaly.
(C) zero Bouguer anomaly and negative free-air anomaly.
(D) positive Bouguer anomaly and zero free-air anomaly.
GATE 2016
Q.18 Which one of the following geophysical methods is most suitable for the exploration of a horizontally stratified graphite deposit at a depth of 50 m?
(A) Gravity (B) Magnetic (C) Radiometric (D) Electromagnetic
GATE 2016
Q.32 The value of free-air correction (assuming sea level as datum plane) at an elevation of 150 m is _________ mGal.
GATE 2016
Q.33 A spherical cavity of radius 8 m has its centre 15 m below the surface. If the cavity is full of sediments of density 1.5?103 kg/m3 and is in a rock body of density 2.4?103 kg/m3, the maximum value of its gravity anomaly is __________ mGa
GATE 2016
Q.34 Match the items (listed in Group I) with the corresponding corrections applied for reduction of marine gravity data (listed in Group II).
Group I
P. Effect of rotating homogeneous ellipsoidal Earth
Q. Effect of deficit mass from mean sea level to average depth
R. Effect of relative motion of ship with respect to revolving Earth
S. Effect of elastic creep of gravimeter spring system and Earth tides
Group II
1.Drift correction
2. Latitude correction to ocean floor
3. Bouguer correction
4. Eotvos correction
(A) P-4; Q-3; R-1; S-2
(B) P-2; Q-3; R-4; S-1
(C) P-4; Q-1; R-2; S-3
(D) P-3; Q-1; R-4; S-2
GATE 2015
Q.45 The Bouguer anomaly obtained after applying all necessary corrections is due to
(A) topographic undulations above the datum
(B) increase in densities of crustal rocks with depth
(C) lateral density variations
(D) vertical density contrast across Moho
GATE 2015
Q.47 A spherical body with its centre located at a depth of 1040 m gives a symmetric residual gravity anomaly high with Δgmax = 5.2 mGal. If the same anomaly were to be obtained over a 2-D horizontal cylinder, the depth to the centre of the horizontal cylinder (in m) is_______.
GATE 2014
Q.10 The International Gravity Formula predicts the theoretical gravity value at a given point assuming a
(A) non-rotating homogeneous spherical earth model
(B) rotating inhomogeneous spherical earth model
(C) rotating homogeneous oblate spheroidal earth model
(D) rotating inhomogeneous oblate spheroidal earth model
GATE 2014
Q.37 The Poisson’s relation linking the gravity and magnetic potentials assumes the same anomaly source with
(A) inhomogeneous density and intensity of magnetization
(B) uniform density contrast and inhomogeneous intensity of magnetization
(C) uniform density contrast and homogeneous intensity of magnetization
(D) inhomogeneous density and homogeneous intensity of magnetization
GATE 2014
Q.52 Compute the maximum value of gravity anomaly in µGal over a buried sphere from the following data:
Radius of a sphere = 5 m
Density contrast = 0.1 gm/cc
Depth to centre of sphere =11 m
G = 6.673x10-8 dyne-cm2/gm2
(A) 2887.58
(B) 288.76
(C) 28.88
(D) 2.89
GATE 2013
Q.37 If L, B, F and T respectively stand for Latitude correction, Bouguer correction, Free-air correction and Terrain correction, then the order in which they will have to be applied for gravity data analysis is
(A) LFBT (B) LBTF (C) FLBT (D) TBLF
GATE 2013
Q.40 Which of the following is useful to estimate the depth to the centre of a spherical body from a gravity anomaly curve?
(A) Surface integration
(B) Volume integration
(C) Twice the absolute maximum
(D) Half-width of the anomaly
GATE 2012
Q.9 Bouguer correction is applied to correct for the gravity anomaly due to mass between station location and
(A) mean sea level (C) base of upper crust (B) local datum plane (D) Mohorovicic discontinuity
GATE 2012
Q.36 The change in gravity caused by Earth’s tides on the land surface in a complete tidal cycle is in the range of (in milligal)
(A) 0.1 to 0.2
(C) 0.3 to 0.4
(B) 0.2 to 0.3
(D) 0.4 to 0.5
GATE 2011
Q.21
The acceleration due to gravity (g) and universal gravitational constant (G) are related by the expression (Me and Re are the mass and radius of the earth, respectively)
GATE 2011
Q.34
Gravity measurement is made on a ship sailing at the speed of 6 knots in the direction N65?E at 20?N latitude. The Eotvos correction (in mGal) is
(A) +38.5 (B) +24.5 (C) -35.5(D) -39.5.
GATE 2011
Q.35 Isostatic residual anomaly over a mountainous terrain is due to (D) ?39.5
(A) gravitational effect of compensating mass
(B) long wavelength variations of topography
(C) short wavelength variations of topography
(D) density inhomogeneities in the upper and middle crust
GATE 2011
Statement for Linked Answer Questions 52 and 53:
A gravity survey is conducted over a highly compact ore deposit (spherical shape). Bouguer anomaly values reduced along a profile are given below.
Q.52 What is the depth to the center of the ore deposit?
(A) 3100 m
(B) 1820 m
(C) 1560 m
(D) 1450 m
Q.53 What is the excess mass (in metric tons) by the deposit?
(A) 1.615 X 10^8
(B) 2.165 X 10^8
(C) 1.312 X 10^9
(D) 1.825 X 10^9
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