Seismic Evidence Explorer

Unit 3 Investigation 1: How can waves reveal what is inside Earth?

Choose a simulation view

Select one of the three tabs above to begin. The simulation opens with no wave paths showing until you choose a tab.

Compare P-wave and S-wave motion

P-WAVEParticle motion is parallel to wave travel.

Observation prompt

What difference do you notice between particle motion in the P-wave and S-wave models?

Test the material

Choose a wave and material, then run a trial.
SOLID MATERIALSourceDetector

Record the pattern

P-wave through solid: ______
P-wave through liquid: ______
S-wave through solid: ______
S-wave through liquid: ______
What pattern do you notice?

Waves & Shadow Zones

P-waveS-waveP- and S-wave paths are intentionally shown with different patterns.
Crust Mantle Outer Coreliquid Inner Coresolid Epicenter P-wave shadow zone P-wave shadow zone S-wave shadow zone — no direct S-wave arrivals Both P & SBoth P & SNo direct P or SNo direct P or SP waves only — no direct S waves

Simplified instructional model. S-waves travel only through solid crust and mantle; the deepest S-wave paths turn outward as soon as they reach the liquid outer-core boundary. P-waves continue through the liquid outer core, refract, and reappear on the far side. The gaps between direct ray families are seismic shadow zones.

What to notice

1. Compare the P-wave and S-wave patterns. How are their paths different?
2. What happens to the deepest S-wave paths when they reach the mantle–outer-core boundary?
3. Why are there no S-wave paths inside the liquid outer core?
4. Follow the P-wave paths. How do they change direction as they enter and leave the core?
5. Locate the empty regions between direct ray paths. Why are these called shadow zones?
Evidence question: How can the different P-wave and S-wave patterns provide indirect evidence about the physical properties of Earth's interior?