Which type of wave, called S waves, move slower than P waves in the Earth's crust?

S waves, or shear waves, are a type of seismic wave that move through the Earth as transverse waves. This means they propagate by causing particles of the material to move perpendicular to the direction of wave travel. In contrast, P waves, or primary waves, are compressional waves that move particles in a longitudinal manner, causing them to move back and forth in the same direction as the wave.

S waves are indeed slower than P waves, which is a critical aspect in understanding the dynamics of seismic activity. This difference in speed is a key factor used in seismology to determine the location and depth of an earthquake's origin, as the arrival times of these waves at seismic monitoring stations are analyzed.

The distinction between S waves as transverse waves and the other types listed helps clarify the nature of seismic wave propagation in geological contexts. Body waves encompass both P waves and S waves, while surface waves travel along the Earth's surface and are typically slower than both body wave types. Longitudinal waves refer specifically to the movement pattern of P waves, highlighting the reason S waves, designated as transverse waves, take longer to arrive at monitoring stations.