Foo Fighters New Zealand gig causes 'volcanic tremor'
Scientists in New Zealand have compared the vibrations recorded during a gig by Foo Fighters to that of a volcanic tremor.
Geologists monitored the earth's movements in the local area as Dave Grohl's band performed at Western Springs on Tuesday evening.
According to the Auckland GeoNet blog the vibrations from the gig emitted a "strong low signal".
"The ground was shaking three times per second in a nice rhythmic motion."
The recordings were taken at two monitoring stations located 1.5km (0.9m) and 2km (1.2m) from the concert.
"The signal is similar to volcanic tremor that is recorded at places like Mt Ruapehu and White Island," the blog stated.
"However the strong correlation in time with the Foo Fighters concert and the fact it was only recorded on the two stations close to Western Springs assured us it was of man-made origin."
The said the "biggest shakes" were registered as the group took to the stage at 8.20pm.
"There are lulls in the signal between the songs and peaks in signal intensity during the songs."
They described the movements as "a semi-continuous harmonic signal with a peak osculation of 3Hz (Hertz)".
It continued: "The cause of the shaking is most likely the weight of the 50,000 fans dancing, as 50,000 fans is equal to around 5,000 tonnes of mass moving (or moshing) on the ground.
"This set up a nice harmonic vibration in the ground which was recorded in our nearby borehole seismometers."