Geophysical Methods in Engineering MCQs Questions & Answers

1

Which geophysical method uses electrical resistivity to study subsurface layers?

A) Seismic reflection B) Electrical resistivity method C) Gravity method D) Magnetic method

Discuss

Answer & Solution

Answer: Option B

Solution:

Electrical resistivity method involves passing current into the ground and measuring voltage difference.This helps identify variations in subsurface resistivity, useful in detecting water tables, clay layers, and voids.

2

What is the primary physical property measured in the seismic refraction method?

A) Electrical resistivity B) Density C) Seismic wave velocity D) Magnetic susceptibility

Discuss

Answer & Solution

Answer: Option C

Solution:

Seismic refraction measures the velocity of seismic waves through subsurface materials.This helps determine layer depths and types of rocks or soils based on their stiffness.

3

The magnetic method in geophysics is used to detect:

A) Density contrasts B) Magnetic anomalies C) Water table depth D) Pore pressure

Discuss

Answer & Solution

Answer: Option B

Solution:

The magnetic method measures variations in the Earth�s magnetic field.It is effective in identifying buried ferrous objects, faults, and igneous bodies.

4

Ground Penetrating Radar (GPR) is most effective in detecting:

A) Subsurface water B) Magnetic minerals C) Airborne pollutants D) Earthquakes

Discuss

Answer & Solution

Answer: Option A

Solution:

GPR uses high-frequency electromagnetic waves to detect changes in material properties like water content, voids, and buried objects.

5

Which of the following is a passive geophysical method?

A) Electrical resistivity survey B) Magnetic survey C) Induced polarization D) Seismic refraction

Discuss

Answer & Solution

Answer: Option B

Solution:

Magnetic surveys are passive as they record natural magnetic field variations without injecting any energy into the ground.

6

Which geophysical method is best for determining the depth to bedrock?

A) Gravity method B) Seismic refraction C) Magnetic method D) Electrical self-potential

Discuss

Answer & Solution

Answer: Option B

Solution:

Seismic refraction helps locate depth to hard layers like bedrock by analyzing refracted wave paths at layer boundaries.

7

The gravity method is based on the measurement of:

A) Wave amplitude B) Electrical potential C) Gravitational acceleration variations D) Magnetic field strength

Discuss

Answer & Solution

Answer: Option C

Solution:

Gravity surveys measure small variations in Earth�s gravity field caused by density differences in subsurface materials.

8

Which geophysical technique is commonly used in groundwater exploration?

A) Magnetic method B) Self-potential method C) Gravity survey D) Resistivity method

Discuss

Answer & Solution

Answer: Option D

Solution:

The resistivity method is ideal for groundwater surveys as water-bearing formations usually show lower resistivity compared to dry rocks.

9

Which of the following is a limitation of GPR?

A) Cannot detect metals B) Ineffective in clay-rich soils C) Requires explosives D) Can only be used offshore

Discuss

Answer & Solution

Answer: Option B

Solution:

GPR is less effective in clayey soils because clay absorbs and scatters radar signals due to its high conductivity.

10

What does a low resistivity reading usually indicate in a resistivity survey?

A) Dense rock B) Dry sand C) Moist clay or water-saturated soil D) Air-filled cavity

Discuss

Answer & Solution

Answer: Option C

Solution:

Low resistivity typically indicates moist or conductive materials like clay or saturated soils.

Geophysical Methods in Engineering MCQs Questions & Answers | Geological Engineering