Earth and Space Science / Unit 4: Earthquakes and Volcanoes
4.3 Seismic Waves
Notes
Earthquakes produce seismic waves.
- P waves (primary): compressional, fastest, arrive first, travel through solids, liquids and gases.
- S waves (secondary): shear, slower, arrive second, travel only through solids.
- Surface waves: slowest, travel along the ground and cause most damage.
- S waves do not pass through the liquid outer core, creating an S-wave shadow zone. This is evidence for the liquid outer core.
- A seismograph records the waves as a seismogram.
Practice
Which wave arrives first at a seismograph?
P waves are the fastest.
S waves cannot travel through the outer core because it is:
Shear waves cannot move through liquids.
Which waves usually cause the most damage?
They have large amplitude and shake the ground at the surface.
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