Seismicity Induced by Waste Water Injection in Complex Fault Systems

Date: 4/26/2019

Time: 08:30 AM

Room: Cascade I

In recent years there was an increase in the seismicity level in several areas across the United States. It is believed that this increase is caused by the human activities, mainly injection of the waste water coming from the unconventional hydrocarbons production. Some of these induced earthquakes exceeded magnitude 5.0 which in combination with the shallow depths of their hypocenters makes them potentially dangerous to the surface structures. These earthquakes can be triggered not only solely due to the fluid flow but also because of the stress perturbations caused by the rupture propagation on nearby faults (or other segments of the same fault). These interactions can lead to either increased size of the single earthquakes or the sequence of several significant seismic events. Moreover, seismic hazard estimation with classical methods is difficult to be assessed. For example, the earthquake sequence near Cushing (OK) from 2015 to 2016 occurred on a previously unmapped fault. Moreover, there are multiple strike-slip faults in the region that are close to one another and can be potentially activated in the future. Therefore, in this study we use physics-based, integrated modeling of fluid flow in deformable media with dynamic rupture propagation to investigate this kind of interactions and their impact on seismic hazard assessment. We performed a series of simulations on step-over strike-slip faults. We found that depending on the geometry (including relative position) of faults and injection wells the main causative factor could be the perturbation of pore pressure and/or stress caused by fluid flow, or the transfer of stress from one fault to another due to dynamic rupturing process. They also produce different patterns of ground motion, potentially allowing to distinguish them on seismograms. These results can be useful for regulatory agencies and oil and gas companies.

Presenting Author: Dawid Szafranski

Authors