9316940 Logan It has been known for sometime that pore fluids can dramatically affect the strength of fault zones, but a variety of possible explanations for the phenomena have not been fully resolved. This study will combine experimental deformation experiments on fault materials with detailed field studies and will focus on chemical weakening of clay-rich fault zones. Experimental results on changes in mechanical strength and sample chemistry with changing pore-fluid composition, temperature, pressure, and strain rate will be related to corresponding change in microstructures of the fault gouge. Experimentally-generated fault-zone fabrics will be compared with those in the field. Result will allow evaluation of the relative importance of fluid chemistry on rock behavior in the vicinity of fault zones.
