A byproduct of oil and gas production is a large quantity of toxic wastewater called brine. Well-drillers dispose of brine by injecting it into deep rock formations, where its injection can cause earthquakes. Most quakes are relatively small, but some of them have been large and damaging.

Yet predicting the amount of seismic activity from wastewater injection is difficult because it involves numerous variables. These include the quantity of brine injected, how easily brine can move through the rock, the presence of existing geological faults, and the regional stresses on those faults.

Now a team of Arizona State University-led geoscientists, working under a Department of Energy grant, has developed a method to predict seismic activity from wastewater disposal. The team's study area is in Oklahoma, a state where much frackingactivity has been carried out with a lot of wastewater injection, and where there have been several induced earthquakes producing damage.

The team's paper reporting their findings appeared in the Proceedings of the National Academy of Sciences on July 29, 2019.

"Overall, earthquake hazards increase with background seismic activity, and that results from changes in the crustal stress," says Guang Zhai, a postdoctoral research scientist in ASU's School of Earth and Space Exploration and a visiting assistant researcher at the University of California, Berkeley. "Our focus has been to model the physics of such changes that result from wastewater injection."

Zhai is lead author for the paper, and the other scientists are Manoochehr Shirzaei, associate professor in the School, plus Michael Manga, of UC Berkeley, and Xiaowei Chen, of the University