Here is a theory. I am not suggesting at this time that this is what is actually happening. It is just a conversational type theory.

Forces related to the gravitational pulls of the sun and the moon on the Earth’s crust bend, stretch, and compress different fault zone in different directions depending on where the sun and the moon are in the sky at different times of the month, year, decade etc. And at any given time there will be groups of fault zones which are being subject to critical angle pressures like that.

When a powerful earthquake occurs some of its energy can focus on the different fault zones around the world which are under greater stress at that time. And their rock layers are weakened by it.

Earthquake do not occur immediately in them. Instead the fault zones continue to accumulate strain energy. But some of them now contain a fatal weakness. And when the sun and moon once again move into the right positions in the sky to bend them etc. in a critical direction they begin fracturing, one after another.