Stress maps developed by Stanford University geophysicists provide insight into the nature of the faults associated with recent temblors in Texas and Oklahoma, many of which appear to have been triggered by the injection of wastewater deep underground.

“These maps help explain why injection-induced earthquakes have occurred in some areas, and provide a basis for making quantitative predictions about the potential for seismic activity resulting from fluid injection,” says study co-author Mark Zoback, the Benjamin M. Page Professor of Geophysics in Stanford’s School of Earth, Energy & Environmental Sciences.

Black lines indicate stress orientation in maps of Texas and Oklahoma.Black lines indicate stress orientation in maps of Texas and Oklahoma.The researchers interpreted data donated by oil and gas companies along with information about the faults present in a given area. The analysis reveals which faults are likely to be problematic and why: in areas where induced earthquakes have occurred in Texas and Oklahoma, the scientists show that a relatively small increase of pore pressure – the pressure of fluids within the fractures and cavities of rocks – would have been sufficient to trigger slip.

Many of the recent earthquakes in Texas that have been suspected as being triggered by wastewater injection occurred on faults that – according to the new map – have orientations that are nearly ideal for producing earthquakes. Hence, doing this kind of study in advance of planned injection activities could be helpful.

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