Time since rupture00:00

Magnitude7.5

Focal depth33 km

P-wave S-wave Surface wave

Inspector Hover over the Earth Move the pointer across the layers to read their properties.

Click or drag in the outer 700 km to move the earthquake focus

Seismic Wave Lab

An earthquake shakes the Earth. Waves race through the crust, mantle and core, bending at every layer boundary. Seismographs around the globe record what comes back.

Playback speed 100× Magnitude 7.5 Focal depth 33 km

Seismographs click a trace to inspect a station

What you are seeing

P-waves are compressional and fast (≈6–14 km/s). They travel through solids and liquids, but bend sharply at the liquid outer core, leaving a shadow zone about 104°–140° from the epicentre.
S-waves are shear waves, roughly half as fast. Liquids cannot carry shear, so they stop at the core–mantle boundary — proof the outer core is molten. (They can re-emerge as P-waves inside the core and convert back: SKS.)
Surface waves are slow (~3.6 km/s) but carry most of the destructive energy, especially for shallow quakes.
Rays curve because wave speed changes with depth, and refract or reflect at each boundary (Snell’s law). Phase names: PcP reflects off the core, PKP passes through it, PKIKP goes through the inner core, PP bounces off the surface.

Simplified 1-D model after PREM (Dziewonski & Anderson, 1981), drawn on a 2-D slice. Shortcuts: no amplitude physics beyond geometric spreading, no mode conversions other than at the core–mantle boundary.