Field measurements of fault slow slip and associated seismicity

Friday, 18 December 2015: 09:45
302 (Moscone South)
Yves Guglielmi, Aix Marseille University, Marseille Cedex 03, France; CEREGE, Sedimentary Systems and Reservoirs department, Aix-en-Provence Cedex, France, Frederic Cappa, Géoazur - Université Nice Sophia Antipolis, Valbonne, France, Jean-Philippe Avouac, California Institute of Technology, Geological and Planetary Sciences, Pasadena, CA, United States, Pierre Henry, CNRS, Paris Cedex 16, France and Derek Elsworth, Pennsylvania State University Main Campus, Energy and Mineral Engineering and Geosciences, EMS Energy Institute, G3, University Park, PA, United States
We show results of slow slip (1-to-10 micrometers/seconds) activations along faults in carbonates and in shales using a hydromechanical in situ testing method. A controlled step-rate injection of a given water volume is conducted between two inflatable packers in an uncased borehole, to produce elastic and inelastic deformations of the surrounding fractured rock mass, with synchronously monitoring of borehole fluid pressure and wall deformation with a specially designed probe. The transition between elastic/inelastic slip occurs at the fault extension pressure (FEP) at the onset of injection flowrate increase. In a typical test, the FEP transition associated with the characterization of the activated slip (strike and dip) on the faults may be used for calibration in a slip sensitivity study related to the ambient stress field. The potential use of the post FEP’s response to estimate the variation of the friction coefficient as a function of slip, slip rate and other static controls is discussed taking different in situ test examples. We show that permeability increase may be a predominant control on fault stability and induced seismicity.