EARTHQUAKES AS A COUPLED SHEAR-STRESS HIGH PORE PRESSURE DYNAMICAL SYSTEM

The migration, coalescence and localization of slip, seismicity, and z ones of high pore pressure are modeled using a porosity reduction mech anism to drive pore pressure within a fault zone in excess of hydrosta tic. Increased pore pressure in discrete cells creates zones of low ef fective stress, which induces slip that may propagate to surrounding c ells depending on the local state of stress. At slip, stress is transf erred using the solution for a rectangular dislocation in an elastic h alf-space, and pore pressures are redistributed by conserving fluid ma ss. Using simple assumptions about fault rheology and permeability, it is shown that the interaction between shear stress and effective stre ss evolves to a state of earthquake clustering with repeated events, l ocked zones, and large variations in fault strength. The model evolves from a uniform shear stress state on a strong fault, to a heterogeneo us shear stress state on a weak fault.