Ge277-Experimental Rock Frictionimplication for seismic faulting

Some other references:

Byerlee, 1978; Dieterich, 1979; Ruina, 1983; Tse and Rice, 1986; Blanpied et al, 1991; Chester, 1995; Lockner et Beeler, 1999; Cocco and Bizarri, 2002

Review articles by - Scholz (1998): ‘Earthquakes and Friction Laws’- Chris Marone (1998): ‘ Laboratory derived friction laws and their application to seismic faulting

• Earthquakes result from frictional instabilities (Brace and Byerlee, 1966)

• Whether friction is stable or unstable determines the mode of slip (seismic vs aseismic)

• The stability of frictional sliding is not a rheological property. It depends of key parameters including– Temperature– Amplitude of stress change– ‘Stiffness’ of the fault (length of the slipping patch)– Effective normal stress

Friction Experiments

(Scholz, 1990)

(Scholz, 1990)

Slip hardening Slip weakening

Friction coefficient is generally of the order of 0.6 for most rock types(Byerlee, 1978)

The shear stress at Frictional yield depends linearly on normal stress

Friction behavior for a wide range of materials is shown for step changes in load point velocity (Dieterich & Kilgore 1994).

Experimental data show that, whatever the material considered, friction depends on sliding rate and that changes in slip rates are followed by a transient adjustment .

(Marone, 1998)

Dc

Static friction depends on hold time and dynamic friction decreases with slip rate. These phenomena contribute to an (apparent) slip-weakening friction law.

Premonitory slip before unstable sliding

(Lockner and Beeler, 1999)

(Lockner and Beeler, 1999)

(Lockner and Beeler, 1999)

Premonitory slip before unstable sliding

Constant stress experiment (creep experiment).

In creep experiments three stages are generally observed, primary, secondary and tertiary creep leading to failure.The sample ultimately fails by Static Fatigue following sub-critical crack growth. Rock strength is time dependent.

(Lockner, 1998)