The effect of Poisson's ratio on the creation of tensile branches around dynamic faults

Abstract

It is common for the fractured zone around dynamic faults to contain tensile cracks. The effect of Poisson's ratio (ν) on the creation of these cracks was investigated in this study as a function of the dynamic minimum strain energy density criterion (MSED-Criterion). In addition, the effect of rupture speed (c), friction coefficient (f), fault inclination angle (β) and confining stress (Ko) were taken into account. The MSED-Criterion permits the study of the creation of tensile cracks in brittle and ductile shear zones. It was found that by increasing Poisson's ratio, the rock behavior transfers gradually from brittle to ductile and as a consequence, the branching angle and fracture toughness increase. Whenever the rock mass tends towards ductile behavior, the possibility of creating tensile branches decreases. Ductile shear zones can sustain stresses greater than brittle zones before tensile branches are formed around dynamic faults. The branching angle of tensile cracks is directly proportional to (ν, c, β, f and Ko) and it varies between approximately 77° and 115°. These cracks are formed in the extensional side of a dynamic fault and they tend to grow towards the maximum far-field stress. The results of this study can be used in the field of earth science and earthquakes to identify the formation of tensile branches around dynamic shear ruptures and they were explained depending on experimental results and field observations of other studies.