Examkin

Question

Difficulty: MediumPhysical Geography of the World

Consider the following statements regarding the propagation of seismic waves through the Earth's interior:

1. Primary waves (PP-waves) are longitudinal in nature and can pass through solid, liquid, and gaseous media.
2. Secondary waves (SS-waves) are transverse waves and can travel only through solid materials.
3. The shadow zone for SS-waves is smaller in spatial extent than the shadow zone for PP-waves.

Which of the statements given above is/are correct?

  1. 1 and 2 onlyAnswer
  2. B
    2 and 3 only
  3. C
    1 and 3 only
  4. D
    1, 2 and 3

Answer

1 and 2 only
The correct response identifies statements 1 and 2 as accurate. PP-waves are compressional (longitudinal) waves capable of propagating through solids, liquids, and gases. SS-waves are shear (transverse) waves that propagate exclusively through solids. The SS-wave shadow zone is significantly larger than the PP-wave shadow zone because SS-waves cannot pass through the liquid outer core, receiving no direct SS-waves beyond 103∘103^\circ from the epicenter worldwide.

Step-by-Step Solution

1
Evaluate Statement 1 regarding P-waves
Statement 1 is correct. Primary waves are longitudinal waves where particles vibrate parallel to wave direction; they travel through solids, liquids, and gases.
Compressional mechanics allow longitudinal motion across all material states.
2
Evaluate Statement 2 regarding S-waves
Statement 2 is correct. Secondary waves are transverse shear waves; liquid media lack shear strength, so S-waves pass only through solids.
Fluid bodies cannot sustain shear stress.
3
Evaluate Statement 3 comparing shadow zone extents
Statement 3 is incorrect. Because S-waves cannot travel through the liquid outer core, their shadow zone forms an extensive zone beyond 103∘103^\circ from the epicenter. In contrast, the P-wave shadow zone exists only as a band between 103∘103^\circ and 142∘142^\circ. Thus, the S-wave shadow zone is significantly larger.
Complete blockage of S-waves by the liquid outer core creates a larger global shadow area than the refractive bending of P-waves.

Key Concept

Seismic wave properties and Earth's interior shadow zones
Rate this question

Topics

Physical Geography of the World

More questions from this topic