Seismic and aseismic slip in EGS reservoir: an experimental approach

Abstract

Observations in EGS reservoirs of induced seismicity and slow propagating ruptures on related faults suggest a close link between the two phenomena. Here we present laboratory experiments that explore, in great detail, the deformation processes of heterogeneous interfaces in the brittle-creep regime. We track the evolution of an interfacial crack over 7 orders of magnitude in time and 5 orders of magnitude in space using optical and acoustic sensors. We show that seismic event occurrences in time and space are in strong relation with the development of the aseismic motion recorded during the experiments. We also infer the statistical properties of the organization of the seismicity that show strong space-time clustering. We finally link our results to the seismicity recorded during hydraulic stimulation in the Soultz-sous-Forêts deep geothermal reservoir in order to show how aseismic processes drive this seismicity with little effects of the fluid pressure.