Source characteristics of seismicity associated with underground wastewater disposal; a case study from the 2008 Dallas-Fort Worth earthquake sequence

Oil and natural gas production from shale formations using hydraulic fracturing or "hydrofracking" techniques has grown rapidly since 2008 and represents a vital and growing domestic energy resource. The waste fluids from increased production (called "brine") are typically injected into deep underground disposal wells to avoid discharge into streams and other sensitive drinking water supplies. The Environmental Protection Agency estimates that approximately 400 million gallons of brine are currently disposed of on a daily basis in more than 28,000 wells in the United States, and the volume of injection continues to grow dramatically. This process has recently been implicated as the source of some potentially induced seismicity in gas-producing states such as Oklahoma, Texas, Arkansas, and Ohio.