Chapter 6 - Slip and Fluid Flow Around an Extensional Fault

Abstract

This chapter models the movement of an extensional or normal fault that affects a fractured layer above a basement block. Displacement of the basement block induces deformation with resultant dilation and slip within the overlying fractured rock mass. The chapter discusses fluid pressure and fluid flow in the region quantitatively and examines the dynamic fluid–fault interactions. A modeling technique is described for an initial model involving a relatively simple planar fault zone at shallow depths (0 to 40 m) where the fluid pressure is assumed to be hydrostatic. The behavior at greater depths (2 km) with suprahydrostatic fluid pressures is discussed in the chapter. The geometry of the fault zone is modified to incorporate dilational and antidilational jogs. Numerical modeling has been used to model fluid flow and deformation in extensional fault regions. The results suggest that fault slip has a significant effect on the distribution of dilation, fluid pressure fluctuation, stress redistribution, and fluid flow.