A record number of 907 earthquakes of magnitude greater or equal to 3.0 was reported in Oklahoma during 2015. A new study investigated the relationship between seismic activity and wastewater injection in the hope of aiding the regulators in reducing a risk of affecting the seismicity in the region.
The rate of quakes in Oklahoma has increased by about 4 000% over the last eight years. The collected seismic data has provided the researchers with an opportunity to investigate the relationship between the increased seismic activity and fluid injection.
In the process of fluid injection, the wastewater and other fluids are pushed deep into underground wells or reservoirs. Such a procedure is also frequently used as a means of disposing of the water previously used in hydraulic fracturing and similar industrial processes which render the water unsafe for disposing into the environment.
According to Pengyun Wang, a Ph.D. student at Civil and Environmental Engineering (CEE), the diffusion of injected fluids can reach the nearby stressed fault lines, which may lead to fault slipping and cause earthquakes.
The researchers have investigated statistical methods for early detection of changes in seismic rates associated with wastewater injection and have worked to quantify the seismicity intensity over time.
The modeling results will hopefully be able to aid the regulators in supervising the wastewater injection and make better decisions when deciding on where and when to inject or store the wastewater. The regulators will also be able to utilize the model for evaluating their individual situations in order to reduce the risk of affecting the seismicity in the area.
The scientists hope to develop the model further in order to project the past seismic trends into the future by performing a comparison between seismic readings and injection data and see how and if they correlate.
"I hope this research will be useful in decision-making by revealing the past evolution of induced seismicity in the region. If local residents of the area are experiencing the negative effects of increased seismicity and want to do something about it, without scientific evidence like this, these people might be powerless to argue against the owners of the wells. But if you can somehow give them evidence, I think it can improve overall awareness of the issue," explained Wang.
- "Statistical Method for Early Detection of Changes in Seismic Rate Associated with Wastewater Injections" - Pengyun Wang, Matteo Pozzi, Mitchell J. Small, and William Harbert - Bulletin of the Seismological Society of America (2016) - doi: 10.1785/0120150038
"A Bayesian Approach for Assessing Seismic Transitions Associated with Wastewater Injections" - Pengyun Wang, Mitchell J. Small, William Harbert, Matteo Pozzi - Bulletin of the Seismological Society of America (2016) - DOI: 10.1785/0120150200
Featured image credit: USGS