Consider the following statements with reference to Secondary waves (S-Waves) generated during an earthquake : 1. They create troughs and crests in the material through which they pass. 2. The direction of vibrations of S-waves is perpendicular to the wave direction in the vertical plane. Which of the statements given above is/are correct ?

Secondary waves (S-waves) are transverse or shear waves that arrive after P-waves during an earthquake [1]. Statement 1 is correct because S-waves, being transverse, cause the medium to vibrate perpendicular to the direction of wave propagation, thereby creating troughs and crests in the material [1]. Statement 2 is also correct; S-waves are characterized by particle motion that is perpendicular to the direction of travel [2]. Specifically, they can be polarized into two components: SV-waves, where the vibration occurs in the vertical plane, and SH-waves, where it occurs in the horizontal plane [1]. In the case of SV-waves, the direction of vibration is indeed perpendicular to the wave direction within the vertical plane [2]. Consequently, both statements accurately describe the physical properties and motion characteristics of seismic S-waves.

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 4: Earths Interior > Secondary Waves (S-Waves) > p. 62
2. [2] https://en.wikipedia.org/wiki/S_wave