Sound unleashes strength beneath surface – SantaFeNewMexican.com
The ground doesn’t quickly forget the loud pumping guitar riffs of an outdoor AC/DC concert.
It remembers the sound for 24 hours or longer, well after the band has packed up and the throngs of screaming fans have left the area.
This memory isn’t something you can see, not with the naked eye. But if you pass the same sound through the ground again in that 24-hour phase, the sound wave will travel faster than it did the first time, and gradually slow down until the ground resets a day or two later, said Paul Johnson, a scientist at Los Alamos National Laboratory.
The phenomenon might seem novel on the surface, but inside the earth it could play a major role in how earthquakes propagate and spread.
The sound waves create unseen weaknesses that can make quakes trigger more easily, Johnson said.