Which seismic wave compresses rock and can travel through solids and liquids?

• A. P-waves
• B. S-waves
• C. Surface Waves
• D. Rayleigh Waves

Answer: (A)

P-waves are compressional waves that move by pushing and pulling in the direction of travel. This motion changes the material’s volume, so they can propagate through both solids and liquids, which is why they travel through the Earth’s interior including the liquid outer core. They’re the fastest seismic waves and arrive first on seismographs. In contrast, S-waves shake the ground perpendicular to the travel direction and can only move through solids, not liquids, while surface waves travel along the surface with a rolling motion and don’t pass through fluids in the same way. So the wave that compresses rock and can travel through solids and liquids is the P-wave.