What are the three main types of seismic waves, and how do they differ?

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Accepted Answer

Primary (P) waves are compressional waves that travel fastest, secondary (S) waves are shear waves that cannot travel through liquids, and surface waves travel along Earth's surface and cause the most destruction. The three main types of seismic waves are: Primary (P) waves, which are compressional (longitudinal) waves that travel fastest and can move through solids, liquids, and gases - they cause particles to move back and forth in the direction of wave travel. Secondary (S) waves are shear (transverse) waves that travel slower than P waves and can only move through solids - they cause particles to move perpendicular to the direction of wave travel. Surface waves (Love waves and Rayleigh waves) travel along Earth's surface, move the slowest, but typically cause the most damage because of their large amplitudes.

Sound, light, and heat waves are types of waves found in other areas of physics but are not the categories of seismic waves. Alpha, beta, and gamma refer to types of radioactive decay, not seismic activity. Tidal waves, shock waves, and radio waves are also unrelated to the classification of earthquake-generated seismic waves.

Seismic waves and their properties are essential topics on the DSST Introduction to Geology exam. Students should understand how each wave type travels, why S waves cannot travel through liquids (this is key evidence that Earth's outer core is liquid), how the difference in arrival times of P and S waves at seismograph stations is used to locate earthquake epicenters, and the two subtypes of surface waves (Love waves produce horizontal shearing, Rayleigh waves produce an elliptical rolling motion).

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