P-waves, S-waves, Love & Rayleigh surface waves — propagation through Earth's layers
Compressional waves; material compresses and expands in direction of propagation. Travel through solids AND liquids/gases. Fastest: 5–8 km/s in crust, 13.7 km/s near core. First to arrive at seismograph.
Shear waves; material moves perpendicular to propagation. Travel ONLY through solids — cannot pass through liquid outer core, creating the S-wave shadow zone (>105°). 3–5 km/s in crust.
Horizontal shear surface waves. Faster than Rayleigh (~4.4 km/s). Horizontal polarization only — no vertical component. Most destructive for tall buildings. Named for A.E.H. Love (1911).
Retrograde elliptical motion at surface — like rolling ocean waves. Both vertical + horizontal motion. Slower (~3.5 km/s). Often felt as rolling/heaving motion during earthquakes. Cause most ground damage.