Induced & triggered seismicity
Since about 2009, the rate of earthquakes in the central and eastern U.S. has dramatically increased. Most of this increase has been in Oklahoma, where much of the increase is probably due to injection of water produced along with hydrocarbons. Next door in Texas, earthquakes are less common, but the same rate increase is evident there as well. Industrial activities have been suspected as the cause for some of the Texas events for several decades, but analysis of earthquake triggering mechanisms has usually been done without knowledge of the local stress field.
To address this shortcoming, Mark D. Zoback and I recently published the new Stress Map of Texas, in which we contribute about 200 new robust principal stress magnitudes and compile information about the faulting regime across the area. Principal stress orientations and magnitudes are essential for understanding what triggered past earthquakes and for predicting the pore pressure perturbation needed to trigger future earthquakes. In addition to presenting the new Stress Map, our article focuses in more detail on four places that have experienced recent earthquakes, where we calculate the pore pressure change that could have triggered fault slip.