Calculate the velocity of shear (S) waves in an elastic solid based on its shear modulus and density.
Last updated: March 2026 | By ForgeCalc Engineering
Shear wave velocity (V_s) is the speed at which transverse (shear) waves travel through a solid medium. Unlike longitudinal (P) waves, shear waves involve particle motion perpendicular to the direction of wave propagation.
In seismology and civil engineering, V_s is a critical parameter for site characterization, as it directly relates to the stiffness of the ground and its response to earthquake shaking. Because fluids cannot resist shear, shear waves cannot travel through liquids or gases (V_s = 0).
Where:
• V_s is the shear wave velocity (m/s)
• G is the shear modulus (Pa)
• ρ (rho) is the density of the material (kg/m³)
Shear waves require a medium with shear stiffness (rigidity). Fluids (liquids and gases) have zero shear modulus, meaning they don't resist sliding deformation, so S-waves cannot propagate.
For most rocks and engineering materials, V_s is approximately 50-60% of the P-wave velocity (V_p). The ratio V_p/V_s is a key indicator of material composition and saturation.
V_s30 is the average shear wave velocity in the top 30 meters of the ground. It is the standard parameter used in building codes to classify soil types for seismic design.
It is often measured using geophysical methods like Downhole testing, Crosshole testing, or surface wave analysis (MASW).
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