The Foo Fighters rock. Literally / File photo: Anna Warr)

It's a known fact that Dave Grohl and the Foo Fighters rock.

But did you know that they rock so hard that they shook the earth?

GeoNet detected seismic tremors 1.5-2kms from the Fooies gig at Auckland's Western Springs Speedway the other week.

According to the boffins, "concert vibrations were recorded as a semi continuous harmonic signal with a peak osculation of 3Hz, i.e. the ground was shaking 3 times per second in a nice rhythmic motion...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 for the duration of the concert."