BRAINCAKEEarthquakes
An earthquake releases energy that travels through the Earth as seismic waves. These are detected by seismometers at stations around the world.
P waves (primary waves) are longitudinal. They are the fastest seismic waves, so they arrive first, and they can travel through solids and liquids.
S waves (secondary waves) are transverse. They are slower than P waves and cannot travel through liquids, because a liquid cannot support the shearing motion a transverse wave needs. S waves are not detected on the far side of the Earth from an earthquake. This S-wave shadow zone is evidence that the Earth's outer core is liquid.
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Key terms in this lesson
- longitudinal wave
- A wave in which the oscillations of the medium are parallel to the direction the wave transfers energy.
- transverse wave
- A wave in which the oscillations of the medium are perpendicular to the direction the wave transfers energy.
More in Waves
- Wave Measurements
- Investigating the Speed of Sound
- Pulse Echo Measurements
- Transverse and Longitudinal Waves
- Phase and Phase Difference
- Superposition
- Interference
- Progressive Waves
All 22 lessons in Waves · All Edexcel AS-level Physics topics