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"In a new paper, the researchers report that it was the dancing and jumping movements of the 70,000-plus fans, not the music or sound system, at the August 4 concert that created the seismic waves that have come to be called 'Swift quakes.'" https://www.caltech.edu/about/news/swifities-shake-it-off-and-help-seismologists-solve-mystery-of-how-concertgoers-shake-things-up