Holy cow, just as I was relegating all this to the Scrap Heap of History, the biggest one yet crashes the party.
A perfect strike-slip on the upper shear fault.
This one would hurt. Remember that with the size of these faults, there's no physics that would stop an M 6 or 7 from suddenly popping up. It all depends on the fractal smoothness of the system.
I highly recommend doing what OK is doing, stopping the injection right at the epicentre 'without implying anything'. This calms the public and has all the effect of closing the barn door after the M4.8 horse has bolted. :)
Although this has happened over the border and thus is a Kansas earthquake, the underlying mechanism doesn't give a rat's ass about that. I consider it to be all Oklahoma.
This was strike-slip. I believe that a thrust at this level would pack twice the punch.
Update: Phew. From the news, I believe this earthquake can be relegated to "Completely Ignored and Laughed At."
Update2: Bluff City (pop. 3) has called in an Intensity 7. This is 'Bricks Down' people, or "I'm too drunk to stand." As usual, the TV stations will not get out there. Reconsidered in the light of day, down to 6.
Update3: Structural damage.
Update4: Yeah, totally forgotten - fish wrap, just like the first M5.6. This zone is following the pattern of that first quake, so you never know. And that 6 will be forgotten as well.