According to information published by Physicsworld.com scientists from France, Belgium, and the U.S., say they’ve shown that the noise of a freight train — thrumming motors, squeaks, squeals, and other rolling noises — is sufficient to measure the condition of underlying rock. They apparently demonstrated this by studying the San Jacinto fault east of Los Angeles, and underneath major Union Pacific and BNSF Railway rights-of-way.
Vibrations from passing trains in Southern California are equivalent to minor earthquakes, researchers say, and enable them to observe changes in the Earth without the need for special purpose “high energy seismic sources” otherwise required for the research.
wow i never knew that