When dealing with massive forces working on rock miles deep, a couple feet of frost at the surface is nothing.

There is some evidence that tidal forces can affect the timing of quakes. Most people don't realize that "terra firma" flexes under tidal forces, similar to ocean tides but with a much smaller amplitude. This sound like something easy to test (plot quakes against phase) and the claim is made from time to time, but I don't think is widely accepted.

In any case, last night the Moon was between last-quarter and new, so even that cannot be implicated. This was just movement along an old fault, following years of building forces.