P and S waves travel more slowly in the Moho than they do in the crust or below the asthenosphere because the composition changes from basalt to peridotite which is a more dense rock material which slows the speed of the body waves down.

Question

Quizplus · Accepted Answer

P and S waves actually travel faster in the Moho and below because peridotite, being denser than the rocks in the crust, allows these waves to propagate more quickly. The increase in density and rigidity of materials like peridotite in the mantle compared to the crustal materials facilitates the faster travel of seismic waves.

P and S Waves Travel More Slowly in the Moho