#### Vol. 5, No. 6, 2010

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Numerical simulation of failed zone propagation process and anomalies related to the released energy during a compressive jog intersection

### Xue-Bin Wang, Jin Ma and Li-Qiang Liu

Vol. 5 (2010), No. 6, 1007–1022
##### Abstract

A compressive echelon fault structure is modeled using an explicit finite difference code (FLAC). The Weibull distribution is used to reflect the heterogeneity of elemental parameters. The released elastic strain energies due to shear and tensile failures are calculated using FISH functions. We examine the failed zone propagation process and the temporal and spatial distribution of the released strain energy, emphasizing those during the jog intersection.

A specimen including two parallel faults with an overlap is divided into square elements. Rock and faults are considered as nonhomogeneous materials with uncorrelated mechanical parameters (elastic modulus, tensile strength and cohesion). A Mohr–Coulomb criterion with tension cut-off and a post-peak brittle law are used. During the jog intersection, high values of released tensile strain energy are found at wing failure zones and at fault tips, while high values of released shear strain energy are found at faults. Despite the jog intersection, the released strain energy in the jog is not high.

We also introduce a quantity ${b}_{0}$ describing the slope of the curve connecting the number of failed elements and the energy released. This is similar to the quantity $b$ found in the literature, but is expressed in units of J${}^{-1}$. Before the jog intersection, some anomalies associated with shear sliding of rock blocks along faults can be observed from the number of failed elements (in shear, in tension and in either), the accumulated released strain energy due to shear and tensile failures, the strain energy release rates in shear and in tension, and the value of ${b}_{0}$. As deformation proceeds, the evolution of ${b}_{0}$ is calculated according to two kinds of the released energy: total energy due to shear and tensile failures and shear strain energy. The two exhibit similar behavior, suggesting that the released strain energy in shear is much higher than in tension.

##### Keywords
compressive echelon fault structure, jog intersection, failed zone, released strain energy, heterogeneity, shear failure