Attenuation is the weakening of seismic waves as they move away from the source. This happens because the energy spreads over a larger area (geometric spreading) and is absorbed by the rocks (frictional heating). High-frequency waves attenuate faster than low-frequency waves. ANSWER: (B) The gradual loss of energy and amplitude as seismic waves travel through the Earth.
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Think of attenuation as the “muffling” of sound as you move away from a speaker. In the Earth, waves lose energy every time they move a particle of rock. Soft, hot or fractured rocks (like those near volcanic arcs) attenuate waves very quickly. Conversely, old, cold and solid “cratons” have low attenuation, allowing seismic energy to travel great distances. This is why a magnitude 6.0 earthquake in the Eastern US (low attenuation) is felt over a much larger area than a 6.0 in California (high attenuation/fractured crust).