Seismicity and fault aseismic deformation caused by fluid injection in decametric in-situ experiments

Journal Article · Sat Sep 01 00:00:00 EDT 2018 · Comptes Rendus Geoscience

DOI:https://doi.org/10.1016/j.crte.2018.08.002· OSTI ID:1567151

De Barros, Louis ^[1]; Guglielmi, Yves ^[2]; Rivet, Diane ^[1]; Cappa, Frédéric ^[3]; Duboeuf, Laure ^[1]

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1. Univ. Côte d’Azur, Valbonne (France)
2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Earth and Environmental Science Area
3. Univ. Côte d’Azur, Valbonne (France); Inst. Univ. de France, Paris (France)

Seismicity induced by fluid perturbations became an important societal concern since felt earthquakes (M_w up to 6) occurred after anthropogenic activities. In order to mitigate the risks associated with undesired seismicity, as well as to be able to use the micro-seismicity as a probe for in-depth investigation of fluid-driven processes, it is of crucial importance to understand the links between seismicity, fluid pressure and flow. We have developed a series of in-situ, decameter-scale experiments of fault zone reactivation by controlled fluid injection, in order to improve the near-source geophysical and hydromechanical observations. The deployed geophysical monitoring close to the injection allows one to cover the full frequency range of the fault responses from the static deformation to the very high-frequency seismic emissions (up to 4 kHz). Here, we focus on the microseismicity (M_w ~ –4 to –3) recorded during two fluid injection experiments in low-permeable shale and highly-fractured limestone formations. In both experiments, the spatio-temporal distribution of the seismic events, the energy balance, and the seismic velocity changes of the fractured medium show that most of the deformation does not actually emit seismic signals. The induced deformation is mainly aseismic. Based on these high-resolution multiparametric observations in the near-field, we therefore proposed a new model for injection-induced seismicity: the seismicity is not directly induced by the increasing fluid pressure, but it is rather triggered by the stress perturbations transferred from the aseismic motion caused by the injection.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1567151
• Journal Information: Comptes Rendus Geoscience, Journal Name: Comptes Rendus Geoscience Journal Issue: 8 Vol. 350; ISSN 1631-0713
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
aseismic deformation
fluid-induced seismicity
in-situ decametric experiments
stress transfer