You might not have felt the ground shake, but Canberrans likely heard scores of air force vessels in the sky last Wednesday, sending seismic waves across the capital.
Australian National University researchers recorded seismic activity from the mass flyover, which were part of the festivities for the centenary of the Royal Australian Air Force.
More than 60 aircraft, from the latest technology to World War II relics, soared over Canberra during the event.
Researchers took recordings of each plane from a seismometre in the basement of Parliament House and a portable seismometre placed at the ANU campus.
Professor Meghan Miller said there was a stark difference between readings of propeller and jet engine planes, which had a larger and sharper amplitude.
"What we found interesting was the difference between the jet planes and the propeller planes, specifically the ones in formation," Professor Miller said.
"Multiple jets flying together produce a lot of noise, and then we can we can measure that in terms of ground motion.
"You can't see [on the seismometre] normal planes taking off from Canberra Airport, that's too far away. But these fly-bys were going right over Lake Burley Griffin and Parliament House, so you can see them clearly."
Seismograms of the @AusAirForce#RAAF100 spectacular aircraft flypast in Canberra yesterday. One at Parliament House and one temporary seismic node @ourANU. Clearly different signals from jet engine aircraft versus the propellor aircraft! #RSESrockstars#seismology#AirForce100pic.twitter.com/vvzD7QYEuw— Prof. Meghan S. Miller (@MeghanSMiller) March 31, 2021
The Hercules, a transport plane powered by four turboprop engines, produced the biggest reading.
The F-35A Lightning, "the most advanced stealth fighter in the world" according to the RAAF, also produced a major spike, as did the F-18F Super Hornet.
A separate seismometre was placed on the university campus to read the activity produced by the Roulettes aerobatic display.
Professor Miller said the last-minute decision to take the readings was a fun exercise while watching the performance.
"Most of us were down by the lake and were watching; we were talking about it and [said] we should see if we can see it on the data from Parliament House," Professor Miller said.
If the activity was equated to an earthquake, it would be pretty insignificant, she said.
The team have recorded aircraft before, when jets have flown over Skyfire, as well as the "footquakes" at a Raiders game.
"It's not just earthquakes that we record, we can do all sorts of things. You can record parades ... anything that creates energy that can be transmitted into the ground, we can then record it," Professor Miller said.
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