It turns out the jolt that shook my house last night was a magnitude 4 earthquake centered about 6 miles deep not too far from where I live.
It was a very strange earthquake. There was no rattling, just a strong jolt that felt as if someone had rammed something hard into the front of our house.
No explanation for the quake provided in the local media coverage:
US Geological Survey http://earthquake.usgs.gov/earthquakes/eventpage/us2000419p#general_summary
AZ Republic http://www.azcentral.com/story/news/local/arizona/breaking/2015/11/02/small-earthquake-shakes-black-canyon-city/75026000/
I don't see any fracking activity in the vicinity of the earthquake http://www.drillingmaps.com/fracking.html#.Vje7Qyvw-G0
Just random earth movement I guess...
We live on an active planet.