List of top Geology and Geophysics Questions on Geophysics asked in GATE GG

Consider a medium of uniform resistivity with a pair of source and sink electrodes separated by a distance \( L \), as shown in the figure. The fraction of the input current \( (I) \) that flows horizontally \( (I_x) \) across the median plane between depths \( z_1 = \frac{L}{2} \) and \( z_2 = \frac{L\sqrt{3}}{2} \), is given by \( \frac{I_x}{I} = \frac{L}{\pi} \int_{z_1}^{z_2} \frac{dz}{(L^2/4 + z^2)} \). The value of \( \frac{I_x}{I} \) is equal to 

 

Suppose a mountain at location A is in isostatic equilibrium with a column at location B, which is at sea-level, as shown in the figure. The height of the mountain is 4 km and the thickness of the crust at B is 1 km. Given that the densities of crust and mantle are 2700 kg/m\(^3\) and 3300 kg/m\(^3\), respectively, the thickness of the mountain root (r1) is km. (Answer in integer)

 

Half-life of \(^{14}C\) is 5730 years. Suppose we start with 1 billion \(^{14}C\) atoms, and after a certain interval of time only 125 million \(^{14}C\) atoms remain, the number of half-lives that has elapsed is ________ (Answer in integer).
If seismic signals of periods greater than 10 s are of interest, the minimum sampling frequency should be ________ Hz. (Round off to one decimal place).

Suppose a mountain at location A is in isostatic equilibrium with a column at location B, which is at sea-level, as shown in the figure. The height of the mountain is 4 km and the thickness of the crust at B is 1 km. Given that the densities of crust and mantle are 2700 kg/m\(^3\) and 3300 kg/m\(^3\), respectively, the thickness of the mountain root (r1) is km. (Answer in integer)


 

For a half space composed of 3 layers with resistivities \( \rho_1 \), \( \rho_2 \) and \( \rho_3 \), as shown in the figure, which of the following statements is/are correct about the variation of apparent resistivity with electrode spacing?


 

Which of the following statements is/are correct regarding the properties of the oceanic lithosphere?
Consider ray tracing in an isotropic elastic Earth, with travel time function \( T(x, y, z) \) in Cartesian coordinates. Select the correct option(s).

Consider a ray tomography experiment, where the goal is to estimate the wave velocity of 9 square cells plotted in each of the cases A and B. The ray paths for source-receiver pairs for both these cases are shown in the figure. Select the correct statement.


 

Select the correct statement regarding surface waves and upper mantle structure.
The components \(u\), \(v\), \(w\) of the displacement field along \(x\), \(y\), \(z\) directions, respectively, are given by: \[ u = - \sin(\omega t - kz) \] \[ v = \sin(\omega t - kz) \] \[ w = 0 \] where \(t\), \(k\), and \(\omega\) are time, wavenumber, and angular frequency, respectively. Assuming \(k\) is real, which one of the following describes the wave?
If seismic signals of periods greater than 10 s are of interest, the minimum sampling frequency should be ________ Hz. (Round off to one decimal place).

The following figure shows a region in which rocks in areas A, B and C follow Hooke's law and are subject to the same stress. B exhibits lower strain than both A and C. What can we infer about the nature of B?


 

The following figure shows the GPS data at two stations located near each other at the same latitude. Station A is moving towards the west while station B is moving towards the east. Which one of the following options is correct?


 

Which one of the options is correct about \( \beta^- \) decay?
Which one of the following factors leads to an abrupt increase in density at the mantle–outer core boundary?
In resistivity measurements for a double-dipole system, the apparent resistivity is NOT affected by:
Half-life of \(^{14}C\) is 5730 years. Suppose we start with 1 billion \(^{14}C\) atoms, and after a certain interval of time only 125 million \(^{14}C\) atoms remain, the number of half-lives that has elapsed is ________ (Answer in integer).
F denotes force, A denotes area, L denotes length, and \( \Delta L \) is the change in length due to the applied force. Assuming linear elasticity, select a relationship where the constant of proportionality is a material property independent of the dimensions of the body.