P-waves, S-waves, dispersion, and seismic refraction in layered media
P-waves (primary/pressure waves) compress and expand along the propagation direction — they travel through solids, liquids, and gases. S-waves (secondary/shear waves) displace particles perpendicular to propagation — they only travel through solids. In the Layered Earth model, waves refract at density boundaries following Snell's law. Dispersion occurs when wave speed depends on frequency — different frequencies travel at different speeds, spreading a pulse into a wave train. Click the canvas to add wave sources.