I just saw this map and I am quite amazed. You can only get injection when you have fractured rock lying over the Precambrian, like the Bruce Black Hole. Here you have the main megathrust heading NE and a perfect right-angle transform fault to the NW. You can nominally inject into the fractured limestone but if the volumes are large enough, this frack waste is injected into the granite basement rock.
The fun thing is that you can inject all the deep saltwater you want and there are no earthquakes. Inject gas fracking waste and the earthquakes pop like party balloons. That's what is happening in the upper NE corner of Kansas. The earthquakes are going nuts there, but there's nobody to feel them. But yet, they still happen. Now they are getting m4's every day, soon they'll m5's, and so on.
The Kansas earthquakes are marching down the transform or adjustment fault as they get bigger. The strain field is activating earthquakes on the main zone, coming up to meet them.