Failure of asperities by hydraulically induced fatigue: a model for the generation of intraplate seismicity

dc.contributor.authorNeedham, Daniel L.en
dc.contributor.committeechairCostain, John K.en
dc.contributor.committeememberBollinger, Gilbert A.en
dc.contributor.committeememberSnoke, J. Arthuren
dc.description.abstractA model is proposed in which intraplate earthquakes are triggered by the tensile failure of asperities by subcritical crack growth. The principle subcritical crack growth mechanism is fatigue driven by cyclic tensile stresses within an asperity. Cyclic stresses result from cyclic pore pressure variations which propagate from the Earth's surface because of annual variations in the height of the water table. Asperities are postulated to be porous and permeable masses of saturated host rock hydrologically connected to fluids within an open fracture. Porosity and permeability within asperities are assumed to be due to microcracks within the rock matrix. Tensile stresses within an asperity are due partly to mechanical loads, but pore pressure is the primary Inechanism by which tension is developed and fatigue operates primarily in tension. Fatigue crack growth is enhanced by chemical subcritical crack growth mechanisms such as stress corrosion and these mechatusms are proposed to act in unison. Faulting may be initiated when a population of asperities is either driven to failure by these mechanisms alone or when it is weakened to the point at which it is vulnerable to small applied stresses. Numerical modeling of the interaction of pore pressures and stresses within asperities indicates that a small transient increase of pore pressure on the order of a fraction of a megapascal will increase the tensile stresses within an asperity by a fraction of a megapascal. Consequently, it may be possible for a small increase in pore pressure, due to elevated water table levels, to trigger asperity failure and result in seismicity.en
dc.description.degreeMaster of Scienceen
dc.format.extentviii, 96 leaves, 1 unnumbered plateen
dc.publisherVirginia Techen
dc.relation.isformatofOCLC# 17604756en
dc.rightsIn Copyrighten
dc.subject.lccLD5655.V855 1987.N434en
dc.subject.lcshRocks -- Fatigueen
dc.subject.lcshSeismic wavesen
dc.titleFailure of asperities by hydraulically induced fatigue: a model for the generation of intraplate seismicityen
dc.type.dcmitypeTexten Polytechnic Institute and State Universityen of Scienceen


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