According to Stephen Holditch, from Texas A&M in an article from the August 2012 American Institute of Chemical Engineers Page45, shale gas fracture treatment "does cause small microseismic events. The amount of energy released is equivalent to that of a gallon of milk falling off a counter and hitting the floor. These micorseismci events cannot be felt at the surface. They can, however, be measured with extremely sensitive geophones....Some very minor earthquakes have been associated with long-term water injection, mainly for water disposal. These earthquakes do not happen often, but when one does, simply stopping the injection prevents further earthquakes. ... however, these rare and small earthquakes have not been associated with hydraulic fracturing operations." On page 44 he identifies the Hydraulic fracture fluids to be 90.6 % water, 8.96 % Proppant (most common is sand), other .44% (Acid, Breaker, Bactercide/Biocide, Clay Stabilizar/Controller, Corrosion Inhibitor, Crosslinker, Friction Reducer, Gelling Agent, Iron Control Agent, Scale Inhibitor, Surfactant, pH-Adjusting Agent.) Other than the Acid at .11% all others are less than .08%.