Fig. 6 SWD in the three seismically active areas shown in Fig. 3. SWD in the three seismically active areas shown in Fig. 3. Volumes injected into EOR wells and SWD wells in the Cherokee, Perry, and Jones study areas are shown between 2009 and 2013. Also shown is an upper bound estimate of the volume of hydraulic fracturing flow-back water that was disposed of in each area in any given year. It is clear that most of the saltwater disposed of in SWD is produced water and not flow-back water from hydraulic fracturing. F. Rall Walsh III, and Mark D. Zoback Sci Adv 2015;1:e1500195 Copyright © 2015, The Authors