Shear Wave (S-Wave) Velocity
Shear waves are transverse waves that travel through solids (but not fluids, which have no shear stiffness) by shearing deformation. Their speed is given by Vs = √(G/ρ), where G is the material’s shear modulus and ρ is its density.
This formula is widely used in seismology to characterize soil and rock (S-waves are the slower, more destructive “secondary” waves in earthquakes) and in nondestructive testing of engineering materials. Because it scales with the shear modulus rather than Young’s modulus, S-wave speed is always slower than the corresponding longitudinal (P-wave) speed in the same material.
Last reviewed August 2026