[souryzzi] More earthquakes

Consider a sci-fi disaster scenario: more earthquakes are happening on earth.

What are some vaguely scientifically realistic mechanisms that could be causing them?

A powerful antagonist is mining the earth, perhaps by surreptitiously teleporting material directly out of the earth's core.  The earth settles and shrinks, causing tectonic plates to subduct and rub against each other more.

There's an object in orbit around the earth causing strong tidal forces.  Maybe the moon has been moved.  What orbit would cause lots of earthquakes?  Maybe eccentric with close perigee.

In reality, we're stymied by lack of knowledge: Although the theory of plate tectonics is well accepted, we don't understand what's going on underneath them that causes the plates to move.  Not knowing that, we can't propose realistic scenarios of what might cause then to move more.