It's still worthwhile to monitor smaller quakes because they come in clusters and might precede, else mitigate, larger earthquakes.
The whole process is laid out here:
www.everythingselectric.com/claude-blot/
Claude Blot in 1969 discerned that earthquakes originate in the Benioff zone in the lower reaches of the Earth's crust. These percolate upward with the timing dictated by electrical activity in the upper crust, which in turn is dictated by the immediate electric[o-magnetic]al environment of the Earth.