Abstract
Complex rupture processes are occasionally resolved for weak earthquakes and can reveal a dominant direction of the rupture propagation and the presence and geometry of main slip patches. Finding and characterizing such properties could be important for understanding the nucleation and growth of induced earthquakes. One of the largest earthquakes linked to wastewater injection, the 2016 Mw 5.1 Fairview, Oklahoma earthquake, is analyzed using empirical Green's function techniques to reveal its source complexity. Two subevents are clearly identified and located using a new approach based on relative hypocenter‐centroid location. The first subevent has a magnitude of Mw 5.0 and shows the main rupture propagated toward the NE, in the direction of higher pore pressure perturbations due to wastewater injection. The second subevent appears as an early aftershock with lower magnitude, Mw 4.7. It is located SW of the mainshock in a region of increased Coulomb stress, where most aftershocks relocated.
Plain Language Summary
Understanding the process of nucleation and rupture growth of natural and induced earthquakes is important for the assessment and mitigation of the corresponding time‐dependent hazard. Advanced earthquake source analysis reveals significant properties such as rupture geometry, preferred direction of rupture propagation, and the configuration of main slip patches in an earthquake rupture. This work use the seismic recording of foreshocks and aftershocks to invert the source complexity of one of the largest earthquakes linked to wastewater injection, the 2016 Mw 5.1 Fairview, Oklahoma earthquake. Two subevents are clearly identified and their centroids are located with respect to the hypocenter. The first subevent has a magnitude of Mw 5.0 showing the main rupture propagated toward the NE, in the direction where the most of the wastewater injection activity is concentrated. The second subevent appears as an early aftershock with lower magnitude, Mw 4.7, located SW where most aftershocks were relocated. These results have important implications to discuss the role of anthropogenic stress perturbation in controlling the direction and extent of the earthquake rupture growth.
Key Points
Modeling the Mw 5.1 Fairview induced earthquake complex source by apparent source time functions and relative hypocenter‐centroid location
Identification of two sources, a mainshock and an early aftershock, favored by Coulomb stress changes
Mainshock rupture directivity supports that the rupture growth is controlled by anthropogenic stress perturbation