If we are talking about man-made earthquakes, then we are getting into VLF, very low frequency, transmitters, maybe extremely low frequency area of discussion.
There are existing treaties which ban the creation of earthquakes, even fog and other weathers.
Thing about it I remember was the source generally needed to be at the antipode, or opposite side of the Globe, Earth.
Also, the waves keep bouncing around for a long time afterward, perhaps relying on the cumulative effect of sucessive waves.
It it HAARP related but the signals travel through the Earth's core as sonic waves.
If you are thinking they have to effect, then remember those sonic jewelry cleaners people have.