[mrb]

Tectonic plates are nearly permanently in a "sensitive arrangement", as you say. Compressive, shear, and tensional stress is the normal. Plates accumulate more and more stress over time, until a small trigger causes the plates to slip and release all that energy at once (earthquake).

In other words, tectonic plates are nearly permanently in a state similar to a boulder delicately balanced on top of a mountain.

[hughw]

Right, the potential energy due to stress in the crust could be released to kinetic energy by a falling feather or some cosmic rays, would be the idea. There doesn't need to be the same energy in cosmic rays as released by the earthquake.