Development of a Damage Zone in the Vicinity of a Dynamic Slip on a Tectonic Fault

Abstract—The results of 2D-calculations describing the formation of damage zone during the development of dynamic slip along a horizontal tectonic fault are presented. Different sliding behaviors are investigated, namely, the sub-Rayleigh sliding when rupture velocity V_r is no greater than the velocity of the Rayleigh wave in the medium and supershear when V_r is higher than the velocity of shear waves. The contribution of tensile and shear fracture mechanisms to the development of damage zone in the vicinity of a fault at different depths is considered. The degree of changes in the physical and mechanical properties of the rock massif at different distances from the fault is assessed. It is shown that at large depths, lithostatic stresses completely suppress tensile fracture, and rock fails exclusively due to shear deformation. At shallow depths, however, the tensile fracture mechanism becomes predominant. The stress release associated with the formation of tensile cracks sharply reduces the size of the shear fracture zone which is localized only in the immediate vicinity of the rupture plane. The increase in tensile strength leads to the enlargement of the shear fracture zone. The damage zone in supershear ruptures can have a complex, non-simply-connected structure. The change in the velocity of compression waves C_p by more than 15–20% is only observed in the immediate vicinity (within 10–20 m) of the sliding plane. At larger distances, a change in \(\frac{{dC}}{C}\) is at most 10%. At shallow depths, tensile cracks may occur and propagate quite far from the sliding plane.