I've always wondered if the melting of glaciers would move masses from one place to another and induce some tectonic moves. But the mass is most likely not significant enough; water/ice has a relatively low density after all.
Like in theory it doesn't make sense that el niño causes earthquakes, yet there seems to be more prominent ones during el niño however if both are related to sun cycle/activity it would make more sense (seeing how the moon affects earth as well)
The Stratigraphy department of the International Union of Geological Sciences would be the obvious first port of call.
Follow that up with an off book chat with digital archivists for commercial oil and gas exploration geologists.
Or maybe some once in a rare incident involving coronal mass ejections somehow affecting the core of the planet. Could even be a delayed effect.