Which phenomenon explains why the Mineral, Virginia earthquake in 2011 was felt over long distances whereas comparably sized earthquakes in California are not?

• A. The crust is old and cold in the Eastern US and transmits the waves more effectively
• B. Seismic waves are more energetic in the East
• C. There are more faults closer to the surface in the East
• D. The West is more dense so waves attenuate more

Answer: (A)

Shaking travels farther when the crust transmits seismic waves with minimal damping. The Eastern U.S. sits on ancient, cold, relatively uniform crust that is rigid and less fractured, so seismic waves lose little energy as they propagate. That means energy from quakes can travel long distances with enough amplitude to be felt far away, which is why the Mineral, Virginia event was felt across a wide region even though it wasn’t enormous. In contrast, the Western U.S. has younger, warmer crust with more faults and heterogeneity, which scatters and absorbs energy more readily, causing shaking to die out more quickly with distance. So the idea that the crust is old and cold in the East and transmits waves more effectively best explains the long-range felt shaking. The other statements don’t match how seismic wave attenuation actually works.