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