THE EFFECT OF FRACTURE FILLER COMPOSITION ON THE PARAMETERS OF SHEAR DEFORMATION REGIME

Abstract:

Geomechanical models of different slip mode nucleation and transformation can be developed basing on laboratory experiments, in which regularities of shear deformation of gouge-filled faults are studied. It’s known that the spectrum of possible slip modes is defined by both macroscopic deformation characteristics of the fault and mesoscale structure of fault filler. Small variations of structural parameters of the filler may lead to a radical change of slip mode [1, 2].

This study presents results of laboratory experiments investigating regularities of shear deformation of discontinuities filled with multicomponent granular material. Qualitative correspondence between experimental results and natural phenomena is detected.

The experiments were carried out in the classical “slider model” statement. A granite block slides under shear load on a granite substrate. The contact gap between rough surfaces was filled with a discrete material, which simulated the principal slip zone of a fault. The filler components were quartz sand, salt, glass beads, granite crumb, corundum, clay and pyrophyllite.

An entire spectrum of possible slip modes was obtained - from stable slip to slow-slip events and to regular stick-slip with various coseismic displacements realized per one act of instability. Mixing several components in different proportions, it became possible to trace the gradual transition from stable slip to regular stick-slip, from slow-slip events to fast-slip events. Depending on specific filler component content, increasing the portion of one of the components may lead to both a linear and a non-linear change of slip event moment (a laboratory equivalent of the seismic moment). For different filler compositions durations of equal-moment events may differ by more than two orders of magnitude.

The findings can be very useful for developing geomechnical models of nucleation and transformation of different slip modes observed at natural faults.

The work was supported by RFBR (grant no. 13-05-00780).

1. Mair, K., K. M. Frye, and C. Marone (2002), J.Geophys.Res., 107(B10), 2219.

2. G.G. Kocharyan, V.K. Markov, A.A. Ostapchuk, and D.V. Pavlov (2014), Phys.Mes, 17(2), 123-133.