Seismic Wave Lab

Trigger an earthquake and follow its waves through the Earth. Click near the rim to place seismometers.

Time 00:00

Focal depth 33 km Magnitude 7.0

Playback speed 150×

Seismometers

Each dot is a wave reaching the surface. Gaps are shadow zones: the liquid outer core blocks S-waves and bends P-waves away.

What am I seeing?

P-waves squeeze rock back and forth. They are the fastest and travel through solids and liquids.
S-waves shake rock sideways, about 60% the speed of P. Liquids can’t carry them, so the outer core casts an S shadow beyond ~100° from the epicentre.
P-waves slow down in the liquid core and refract, leaving a P shadow near 100°–140°.
Surface waves are the slowest and the most destructive, running along the crust.
Waves curve because rock gets stiffer with depth, and bend or reflect at layer boundaries (Snell’s law). The S–P delay on a seismogram tells you how far away the quake was.
A simplified 2D model based on average Earth structure. Magnitudes and energies are illustrative.