Seismic Waves (P & S Waves)
Elastic body waves that propagate through Earth's interior during an earthquake, classified as Primary (P) waves and Secondary (S) waves.
Governing formula
v_P = √((K + ⁴/₃ μ) / ρ), v_S = √(μ / ρ)
SI unit
km/s (Seismic Wave Velocities)
In depth
Primary (P) waves are compressional longitudinal waves that travel fastest (~5–8 km/s in crust) through solids, liquids, and gases. Secondary (S) waves are shear transverse waves (~3–4.5 km/s) that travel only through solids, failing to propagate through Earth's liquid outer core.
Examples in the real world
Calculating earthquake epicenter distance using the time lag between P-wave and S-wave arrival times on seismograms.