Systematic observation of a seismic back-front during fluid injection in both natural and anthropogenic earthquake swarms - Ecole Nationale du Génie de l'Eau et de l'Environnement de Strasbourg Accéder directement au contenu
Article Dans Une Revue Earth and Planetary Science Letters Année : 2024

Systematic observation of a seismic back-front during fluid injection in both natural and anthropogenic earthquake swarms

Louis de Barros
Philippe Danré
Frédéric Cappa

Résumé

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.
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Dates et versions

hal-04621492 , version 1 (24-06-2024)

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Louis de Barros, Philippe Danré, Dmitry Garagash, Frédéric Cappa, Olivier Lengliné. Systematic observation of a seismic back-front during fluid injection in both natural and anthropogenic earthquake swarms. Earth and Planetary Science Letters, 2024, 641, pp.118849. ⟨10.1016/j.epsl.2024.118849⟩. ⟨hal-04621492⟩
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