Aftershock Triggering and Spatial Aftershock Zones in Fluid-Driven Settings: Discriminating Induced Seismicity From Natural Swarms

Aftershock cascades play an important role in forecasting seismicity in natural and human-made situations. While their behavior including the spatial aftershock zone has been the focus of many studies in tectonic settings, this is not the case when fluid flows are involved. Using high-quality seismic catalogs, we probe aftershocks dynamics in five settings influenced by fluids: (a) induced seismicity in Oklahoma and Kansas, (b) natural swarms in California and Nevada, and (c) suspected swarms in the Yuha Desert (California). All settings exhibit significant aftershock behavior highlighting the importance of event-event triggering processes. The spatial aftershock zones scale with mainshock magnitude as expected based on the rupture length. While (a) and (b) show a rapid decay beyond their rupture length, (c) exhibits long-range behavior suggesting that fluid migration might not be the dominant mechanism. We also find that the scaling of aftershock productivity with mainshock magnitude together with the Gutenberg-Richter b-value might allow to distinguish between natural swarms and induced seismicity.

Automated summary

Through the study of seismic catalogs, it was found that the dynamics of aftershocks differ when fluids are involved. Different scenarios all show significant aftershock behavior, highlighting the importance of event-event triggering processes. The size of aftershock zones increases with main shock magnitude, and the decay rate of aftershocks varies in different scenarios.