Anisotropic poroelasticity and the response of faulted rock to changes in pore-fluid pressure
David Healy, 2012. "Anisotropic poroelasticity and the response of faulted rock to changes in pore-fluid pressure", Faulting, Fracturing and Igneous Intrusion in the Earth’s Crust, D. Healy, R. W. H. Butler, Z. K. Shipton, R. H. Sibson
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The Law of Effective Stress has found wide application in structural geology, rock mechanics and petroleum geology. The commonly used form of this law relies on an assumption of isotropic porosity. The porosity in and around fluid-saturated fault zones is likely to be dominated by tectonically induced cracks of various shapes and sizes. Previously published field and laboratory data show that these cracks occur in distinct patterns of preferred orientation, and that these patterns vary around the fault zone. This paper uses the more general form of the Law of Effective Stress which incorporates anisotropic poroelasticity to model the geomechanical response of fault zones surrounded by patterns of oriented cracks. Predictions of fault stability in response to fluid pressure changes are shown to depend on both the nature (or symmetry) of the crack pattern and the orientation of the crack patterns with respect to the in situ stress. More complete data on the porosity of natural fault zones will enable more accurate predictions of fault stability in the subsurface.
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Faulting, Fracturing and Igneous Intrusion in the Earth’s Crust
Geologists have long grappled with understanding the mechanical origins of rock deformation. Stress regimes control the nucleation, growth and reactivation of faults and fractures; induce seismic activity; affect the transport of magma; and modulate structural permeability, thereby influencing the redistribution of hydrothermal and hydrocarbon fluids. Experimentalists endeavour to recreate deformation structures observed in nature under controlled stress conditions. Earth scientists studying earthquakes will attempt to monitor or deduce stress changes in the Earth as it actively deforms. All are building upon the pioneering research and concepts of Ernest Masson Anderson, dating back to the start of the twentieth century. This volume celebrates Anderson’s legacy, with 14 original research papers that examine faulting and seismic hazard; structural inheritance; the role of local and regional stress fields; low angle faults and the role of pore fluids; supplemented by reviews of Andersonian approaches and a reprint of his classic paper of 1905.