  A mechanism that explains the increase of electromagnetic (EM) perturbations
during earthquakes is proposed. When earthquakes occur, surface waves propagate
along the globe surface inducing a globe surface rippling, which is reproduced
in an amplified manner at the atmosphere-ionosphere interface. A surface EM
wave that imparts a quiver velocity to electrons propagates along the rippled
interface encountering a periodic plasma density. A non-linear density current
is consequently generated that is a source of EM waves. The wave equation is
solved and the EM field is determined.
