List of top Geophysics Questions

If \(r_1\) and \(r_2\), respectively, denote the equatorial and polar radii of a reference ellipsoid, then the radius, \(R\), of its equivalent sphere is given by

The wavelength of a certain portion of the electromagnetic spectrum ranges from 2000 nm to 3000 nm. The highest frequency associated with the above portion of the spectrum is____________\(\times10^{8}\) MHz (rounded off to one decimal place).

If \(F\) represents the Earth's total magnetic field corresponding to its dipole source only, then the increase in \(F\) from 0\(^\circ\) to 60\(^\circ\) N magnetic latitude is __________ % (rounded off to one decimal place).

What is the value of magnetotelluric impedance phase over a homogeneous half-space?

Analytic signal, \(A(\theta)\), for \(f(\theta) = \cos\theta\) is equal to

If \(\tau\) and \(p\) denote intercept time and slowness, respectively, in the \(\tau-p\) diagram, then which one of the following is CORRECT for a P-wave propagating inside the Earth?

Given the Rayleigh wave velocity \(V_r\), shear wave velocity \(V_s\) and the P-wave velocity \(V_p\), which of the following relationships is/are CORRECT?

If the diameter of a scaled-down model of the Earth is 45 cm, then the equivalent length on the surface of the Earth for 1 cm on the model is _____________ km (rounded off to two decimal places).
[Use: Radius of the Earth = 6371 km]

The vector field \(\mathbf{F}\) for a region is described by \(\mathbf{F} = a r^n \hat{r}\) \((r\neq 0)\), where \(a\) is a non-zero constant and \(r\) is the radial distance from the source. For what value(s) of \(n\), \(\mathbf{F}\) becomes both solenoidal and irrotational?

The given figure shows the geometry of a seismic ray path inside the Earth, with the P-wave velocities of 10 km/s, 11 km/s and 12 km/s corresponding to the layers L1, L2 and L3, respectively. If the angle of incidence (\(\theta\)) at the L1-L2 boundary is \(40^\circ\), then what is the angle of refraction at the L2-L3 boundary? (answer in nearest integer)

(In the figure, \(r_1 = 3100\) km is the radius, measured from the Earth's centre O, of the L1-L2 boundary, and \(r_2 = 3000\) km is the radius of the L2-L3 boundary.)

Which of the following is/are the correct explanation(s) for an increase in the adiabatic temperature gradient from the lower mantle (LM) to the outer core (OC)?

In which one of the following layers inside the Earth, the velocity of the P-wave exceeds 13 km/s?

What happens to the magnetic susceptibility (\(k\)) and remanent magnetization (\(I_r\)), when the molten rock undergoes rapid cooling?

The maximum strain for the plane wave at \(t=0\), having a wavelength of 16 km and unit amplitude, travelling along the X-direction, as shown in the figure, is _______ (rounded off to three decimal places).

Gamma-ray (GR) log values for clean sandstone and shale are 15 API and 115 API, respectively. If GR records 35 API for shaly-sandstone, then the GR index is _____________ (rounded off to one decimal place).

A scintillometer records 300 counts per second (cps) in a radiometric survey. If the background radiation and dead-time of the instrument are 100 cps and 250 \(\mu s\), respectively, then the true net count rate is _______ cps (rounded off to two decimals).

The figure below shows Bouguer gravity anomaly values (in mGal) at a grid interval of 1 km, centred on point P (r1 and r2 are radial distances from P).

The second vertical derivative at P is _________ mGal/km\(^2\) (rounded off to two decimals).

Between \(L_1\) and \(L_2\) norms, which one of the following is CORRECT in the treatment of outliers in the data?

A causal recursive filter is given by \(y_n = x_n - 2x_{n-1} + 3y_{n-1}\). If the input values, \(x_0\), \(x_1\) and \(x_2\) are 1.2, -0.8 and 2.3, respectively, the output, \(y_2\), of the filter is __________ (rounded off to one decimal place).

Which of the following sources is/are used in land seismic surveys?

Which of the following statements about digital filters is/are CORRECT?

If a signal is sampled at a sampling rate of 0.2 ms, then its sampling frequency is ____________kHz.

Which of the following assumptions is/are valid for electromagnetic induction to happen in the Earth?