OK has just as high or higher earthquake risk as CA. I don't know if I believe the fracking/water injection theory or not. It sounds too much like global warming to me. OK is loaded with faults and they haven't done much in a very long time, maybe it is time. Down by Meers, OK was where I saw my first seismograph as a kid and since then I figured OK must be prone to earthquakes, it just took a few decades to realize that feeling. This was a fairly shallow one also, about 3 miles deep, so thankfully is was only a 5.0, much more could have cause much more damage. All in all, this one being limited to property damage was a good thing. It may also get people to earthquake proof their homes to limit damage, you know little things like strapping down your hot water heater.
bob