gravity is an electrical related phenomenon

the gravity of the Earth changes with charge. The problem is, charge distribution will never be uniform, and it will effect the crust unevenly.

- Gravity is not constant through the shell/crust of the planet.

- That creates profound stress on the crust creating earthquakes.

Each part of the crust will be lifted at different rates, and have different gravities. As the charge builds up in a region, then releases like a lightning discharge, you have the earthquake.

This gravity anomaly map is pretty interesting. The areas of highest gravity coincide with active earthquake and volcanic regions.
[link to discovermagazine.com]

and you can take this further

The different geological layers and thermoclines (minus the inner and outer core cos they don't exist) are simply extensions of the Earths magnetosphere. As the magnetosphere is deformed under pressure from the heliosphere/as the Earth is a resistor, embedded in the radial electric field that is the heliosphere, the Earth's magnetic field changes as the strength of the current flowing through the Earth fluctuates due to fluctuations in the sun. Just as the deformation of the thermoclines causes wind, similar deformations in the magnetic field below the surface cause earthquakes
[link to en.wikipedia.org]

and you get some pretty good visuals