Louis De Barros , Philippe Danré , Dmitry Garagash , Frédéric Cappa , Olivier Lengliné
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引用次数: 0
Abstract
Seismic swarms represent clusters of seismicity without large mainshocks. While they occur naturally, they can also be induced by human activities, particularly during reservoir hydraulic stimulations. A striking feature of seismic swarms is the migration of their hypocenters. The seismic front, initially attributed to fluid diffusion, has more recently been understood as the result of the propagation of a fluid-induced aseismic slip. Close to the center of the swarm, a seismic back-front is commonly admitted after the injection end, but a low density of events is also observed during the injection period. In our investigation, based on a compilation of 22 swarms of both natural or anthropogenic origin, we aim to explore the existence and origin of a seismic back-front. Interestingly, we observe a post-injection back-front only in rare cases, where a rapid fluid pressure decrease is imposed at the injection point. Conversely, a back-front during the injection period is always observed in both types of swarms. Consequently, the back-front cannot be reliably used to infer the end of injection, as commonly done for natural swarms. Moreover, the occurrence of this back-front during injection is linked to an increase in the minimum magnitude of seismic events. We interpret the vanishing of the seismicity close to the injection point as a consequence of the increase in earthquake nucleation length with increasing fluid pressure. With a substantially enhanced capability for detecting small events, it may become feasible to use this back-front as a means of monitoring injection pressure, even in the context of natural swarms.
期刊介绍:
Earth and Planetary Science Letters (EPSL) is a leading journal for researchers across the entire Earth and planetary sciences community. It publishes concise, exciting, high-impact articles ("Letters") of broad interest. Its focus is on physical and chemical processes, the evolution and general properties of the Earth and planets - from their deep interiors to their atmospheres. EPSL also includes a Frontiers section, featuring invited high-profile synthesis articles by leading experts on timely topics to bring cutting-edge research to the wider community.