Emergence of a Zone of Disturbed Rock in the Vicinity of Dynamic Slip Along a Tectonic Fault

The article presents results of 2D simulations of formation of a zone of disturbed rock during the development of a dynamic shear along a horizontal tectonic fault. Different sliding regimes are studied: the sub-Rayleigh one (the rupture propagation velocity Vr does not exceed the velocity of Rayleigh wave in the medium) and the supershear one (the Vr value is higher than the velocity of transverse waves). Contributions of tear and shear mechanisms to the process of emerging zone of disturbed rock in the vicinity of a fault at different depths is considered. The degree of alteration in physical and mechanical properties of rock at different distances from the fault is assessed. It is shown that at large depths lithostatic stresses completely suppress rupture, and rock destruction occurs solely due to shear deformation. At shallow depths, the tear mechanism becomes predominant. The stress release associated with emerging of tensile cracks leads to an abrupt decrease of the zone of shear fracture. This zone is localized only in the immediate vicinity of the rupture plane. An increase in the tearing strength leads to an increase in the size of the shear fracture zone. In supershear ruptures, the fracture zone can have a complex, non-simple character. A change in the propagation velocity of longitudinal waves Cp by more than 15-20% occurs only in the immediate vicinity of the slip plane at a distance of 10-20 m. At large distances, the degree of change in the value does not exceed 10%. At shallow depths, there may be tensile cracks that propagate over significant distances from the slip plane.

fault, earthquake, dynamic rupture, destruction of geomaterial, numerical simulations