From the song DEARIE.

"dearie do you remember when Gilda Grey did the shimmy shake ~ that's what started the Frisco quake."

Apparently whenever something is done with a natural rhythm ~ and if it is done in enough houses (or on stage for that matter) at one time ~ then :::: it will set up ((((natural vibrations)))) in the earth ~ and, if strong enough could trigger an earth quake. They don't call the Pacific Ocean the ring of fire for nothing.

Cap't Bob