Denton would know — he used “seismic noise” from a music festival to solve a mystery that plagued his colleagues for years. Seismologists have long associated large, loud events with peaks in seismic activity, but didn’t always agree on what caused the disturbances in the first place. Were seismic spikes caused by moving bodies or just loud music and cheering?
A few years ago, Denton and his colleagues were on hand to help the BBC answer another enduring question: What would happen if everyone in the world jumped up and down at once? The jump took place at the end of a Madness concert at a huge music festival, which they monitored throughout.
After the show, Denton, a Madness fan, began piecing together the seismic readings with live concert footage. At peak moments in songs like “Our House,” the video showed 40,000 attendees dancing wildly, then calming down to catch their breaths. This ebb and flow aligned with spikes in the show’s seismic output.
“The amount of energy generated by people dancing is orders of magnitude larger than the amount generated by the concert’s PA system,” said Denton. The seismic spikes weren't caused by booming music, but by rhythmic dancing.
As it turns out, Madness is a repeat offender in the seismic disturbance category. On at least two different occasions, shows by the band caused nearby buildings to sway, convincing confused neighbors that they were in the midst of an earthquake.
Given the right circumstances, Denton says that 70,000 rhythmically dancing Burners could generate the same result: a spike that could measure a 0.5 on the Richter scale. In fact, the vast expanse of desert “would help with the transmission of the vibrations” of a dancing crowd. The sunbaked lake bed might even have a resonance effect, enhancing the sound’s amplitude as it bounces around the surface. But though the vibrations would “travel quite easily through that kind of solid, dry material,” said Denton, they’d have to be picked up by at least four monitoring stations to be considered a bona fide seismic disturbance.
Though Denton said the shaking wouldn’t hold a candle to something like a quarry blast, which releases a huge amount of potential energy at once, he calculated that 70,000 dancing people would generate an energy input of about 30 kJ per minute…a slow burn, so to speak. In comparison, even the most outrageous sound system (on an art car or otherwise) could only generate an input of 50-100 kilowatts per hour.
There’s just one problem: To be felt by people far from the festivities, the intensity would need to reach a 2.5 or 3 on the Richter scale. (Since the scale is logarithmic, Burning Man would need to sell a vast, impossible number of tickets to reach that point.) Then there’s the fact that a seismic disturbance that isn’t caused by, well, the earth isn’t technically an earthquake. But on the off chance that every attendee taps into the same dancing vibe at the same time over the weekend, know that their celebrations will indeed cause measurable vibrations.