Which seismic wave is characterized by a purely horizontal, side-to-side motion perpendicular to the direction of travel?
Love waves (L-waves) are surface waves that move the ground in a horizontal, shearing motion. They do not have a vertical component. This side-to-side shaking is particularly destructive to buildings because most structures are designed to handle vertical gravity loads but are highly vulnerable to horizontal shear forces. ANSWER: (B) Love waves
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Named after Augustus Edward Hough Love, these waves are “trapped” at the Earth’s surface. While S-waves also move perpendicular to travel, Love waves are restricted to the surface and travel slightly faster than Rayleigh waves. Their motion is purely parallel to the surface, essentially “shaving” the ground back and forth. Because they have a high amplitude and occur at the surface where human infrastructure exists, they are the primary cause of the foundation failures and horizontal “whiplash” damage seen in high-magnitude earthquakes.