Looking that this map with some detail, you can come to this estimate. The Azle sequence was caused by something like the same amount. We don't know the percentage of fracking waste, but since OK is now the only place to inject this stuff, it is somewhere around there.
Now, consider New Madrid thousands of years ago. How much can a natural seep inject into the rock? I think something like 100 barrels a day. So, the beauty of OK is that we are accelerating Nature by 1000 times. It probably took New Madrid thousands of years to proceed to maximum. Now we can do it in just a few years. I am happy to be living this moment. :)