Question

Select the correct statement regarding surface waves and upper mantle structure.

• A. Surface waves cannot be used to infer the upper mantle structure as the amplitudes decay with increasing distance from the surface
• B. Surface waves can be used to infer the upper mantle structure as surface wave phase velocity varies with frequency
• C. Surface waves can be used to infer the upper mantle structure as the shear-wave velocity of the medium changes with frequency
• D. Surface waves cannot be used to infer the upper mantle structure as surface waves travel only along the surface and are not sensitive to the Earth’s internal structure

Hint:

Surface waves are valuable for investigating the Earth's upper mantle due to their sensitivity to the material properties of near-surface layers.

Answer 1

The Correct Option is B

Step 1: Understanding surface waves. 
Surface waves are seismic waves that travel along the Earth's surface. Their characteristics, such as velocity and amplitude, are influenced by the properties of the Earth's surface and near-surface layers. These waves typically have slower velocities compared to body waves (P-waves and S-waves). 
Step 2: Effect of surface wave phase velocity. 
Surface wave phase velocity is frequency-dependent and varies with the elastic properties of the Earth's layers, particularly in the upper mantle. By studying the dispersion (variation with frequency) of surface waves, we can infer information about the structure and properties of the upper mantle.
Step 3: Conclusion. 
Thus, surface waves can indeed be used to infer the upper mantle structure, as the phase velocity of surface waves varies with frequency.