From left to right and back again. The ground sometimes seems to shake during shows like Snollebollekes. Does the pounding of fans cause those vibrations or the music?
In July 2023, an enthusiastic “Swifties” song reportedly caused a veritable earthquake during a Taylor Swift concert. “Ages” Concert at Lumen Field. The seismic activity during the ceremony can be compared to an earthquake measuring 2.3 on the Richter scale. Also here in the Netherlands, the ground regularly shook after evenings of “Left Rechts” by Snollebollekes. To what extent do these tremors compare to earthquakes, and can we learn anything from them?
Scientists have left these questions behind University of Utah to Taylor Swift concerts and placed seismometers (measuring devices that are also typically used to monitor geological activity) in the ground around concert halls where Taylor Swift performed twice. There they collected data during these two shows. The researchers confirmed that the concerts did indeed cause measurable vibrations in the ground. In fact, the seismic signals in the spectrograms (see box) were directly related to the rhythm of the music.
Spectograms vs Earthquakes
Seismograms and spectrograms are two different ways of representing seismic waves. Seismologists use both types of displays to locate earthquakes and determine their magnitude, and to analyze seismic signals and determine the source of those signals. Seismograms are easier to interpret, while spectrograms can provide more information about the frequency content of seismic waves.
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Initially, researchers thought that music caused vibrations. And also because the vibrations were harmonic (a vibration in which deflection and thrust are directly proportional to each other), says research leader Gabrielle Tibb. “My gut feeling was that if you have such a beautiful harmonic signal, it has to come from the music or the instruments.” But it turned out not to be the case. The vibrations were strongest during Taylor Swift's most popular songs. l'get rid of” as the absolute winner, indicating that it was actually due to over 70,000 fans dancing and jumping, which only increased their enthusiasm for the music.
Music and dance
To confirm this theory, scientists conducted another experiment at home. The researchers first played the songs on instruments alongside a powerful measuring instrument and then danced to them as well. This also showed that it was movement and not music that caused the harmonic vibration. Tip thinks this has to do with the shape of the signal. Bass beats have a rounder, more prominent shape than the “peak” of the jump. “This could explain why some seismic signals appear as harmonic in spectrograms, while other similar signals do not.”
Volcanoes
According to Tip, the concert data represents a great opportunity to test methods for detecting seismic signals in spectrograms. “For earthquakes, the signals are usually very sharp and easy to recognize from the waveforms,” Tipp said. “But for volcanoes, for example, there is a wide range of signals whose spectrograms can be very useful in identifying different types of earthquakes,” she explains.
The results can also say something about human behavior. For example, seismic signals can be used to measure the movements of large groups of people. This can be useful in the field of event management, Crowd control And even the psychology of social interaction. Especially in areas with a high risk of earthquakes, it is useful to be able to distinguish signals of a seismic event from real seismic activity. So that everyone doesn't have to evacuate quickly when a very good song is played.
