I’d seen a similar study about natural arches a few years ago.
The striking red rock towers and arch formations peppered throughout Southern Utah and the Colorado Plateau are known to shake and sway in response to earthquakes, high winds, thermal stresses, and other sources of vibration, such as those from helicopters, trains, passing vehicles, and blasts. Being able to assess the stability of these structures, and detect any damage from vibrations, can be challenging. That’s why geologists have been measuring the natural frequencies of these towers for several years now.
I can only imagine what the cliffs at Red Rocks Ampitheater experience during a Grateful Dead concert.