“Shake, Shake, Shake, Shake,” Taylor Swift sings from the stage at Seattle’s Lumen Field at 10:35 pm on July 22. “Shake It Off” is a strong up-tempo song played at 160 beats per minute. For the Pacific Northwest Seismic Network, which is designed to monitor earthquakes, this is a 2.6 Hz signal in which the amplitude of the acceleration was as large as one centimeter per second.
The well-located seismometer first came to public attention in January 2011, when it recorded the reaction of fans of the American football team Seattle Seahawks to running back Marshon Lynch’s spectacular touchdown in what is known as “Beast Mode”. The “Beast Quake” went down in local sports history. When Ms. Swift came to town for two nights of her Eras tour, Jacqueline Caplan-Auerbach, a geology professor at Western Washington University, used the opportunity to explore how events at the stadium affect its surroundings. Are. On December 11, he presented some of his findings at the autumn meeting of the American Geophysical Union in San Francisco.
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In 1985 Bruce Springsteen and the E Street Band shook the Nya Ullevi Stadium in Gothenburg with such force that some spectators became concerned, and caused so much damage to the structure that further concerts there were banned. Later analysis revealed that this was no less than the intensity with which the Mighty Max Weinberg was pounding his drums, although it is an intensity that must be counted. The spectators on the pitch were moving at a frequency that resonated with the soil beneath the stadium and parts of the building.
Dr. Kaplan-Auerbach wanted to see whether this kind of resonant amplification could work elsewhere, and wanted to differentiate between the musical effect and the audience response. Their concert-night data showed two distinct sets of signals, one in high frequencies (30–80 Hz), one in low frequencies (1–8 Hz). High-frequency signals were present during sound check, when the band was on stage but the stadium was empty, and were absent during the concert’s “surprise song”, which was played by Ms Swift alone without the band. The lower frequencies were absent when the audience had yet to arrive. Obviously those high frequencies were from music.
The lower frequency signals varied from song to song to match the tempo of the music; They were apparently inspired by audience reaction rather than general resonance with the building. The harmonics above the main signal are known as the Dirac comb effect in signal analysis, in which a signal repeating at a frequency creates harmonics at multiples of that frequency. Jordi Diaz and colleagues suggested as much in their seismic analysis of another Springsteen concert at Barcelona’s Camp Nou in 2016. But Dr. Kaplan-Auerbach also suggests that they may in some cases reflect differences in fans’ interpretations of them. rhythm.
The impact of the song and Ms. Swift’s performance, as captured on time-stamped photographs of the event taken by fans such as Dr. Caplan-Auerbach’s teenage neighbor (cited in her presentation as a co-author), proved highly replicable, Although the first-night crowd was a bit more energetic (perhaps they were a more committed group of fans). On both occasions when the final refrain of “Love Story” reached its peak with the line, “Take out a ring and say ‘Marry me, Juliet'” the oscillations reached a climax as the singer’s left hand rose triumphantly. .
Overall, the signal was significantly stronger than the original Beast Quake, perhaps because Swifties are coordinated by the beat in a way that football fans are not. But differences in audience demographics and interests may provide greater insight. Veteran heavy-metal band Metallica will play Lumen Field in August 2024. The seismometer will be waiting to see what a little head banging adds to the mix.
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