Influence of the state of faults in lithospheric plates on the starting earthquake

In earlier works the authors have constructed a model of the starting earthquake from the preliminary stage and up to the earthquake itself. The model is based on the boundary problem formulation accepted in a number of works and represents two semi-infinite lithospheric plates with straight boundaries modeled by Kirchhoff plates slowly moving towards each other. The plates are placed on a three-dimensional linearly deformable foundation. It is assumed that the foundation surface is a Conrad boundary separating the top granite and bottom basalt structures of the Earth's crust. For such a boundary problem, we have studied the change in the contact stresses concentration under the lithospheric plates for the cases with and without a distance between the plates and the change in the contact stresses concentration in the convergence zone of the lithospheric plates. When the plates are close to each other, the concentration of stresses in the convergence zone, which is a fault, is singular. According to the experience of solving boundary problems for linear elastic materials, this means the destruction of a zone with such stresses concentration, i.e. the occurrence of an earthquake. For this model, different effects from the impact on the lithospheric plates have been studied. As a result, it was found that the same effects were characteristic for faulting and breaking earthquakes which had actually occurred. The study was carried out for the static problem with vertical external effects on the lithospheric plates assuming no boundary stresses at the ends. The study based on the block element method executed in the present work is aimed at building a more complex model, assuming the presence of stresses, i.e. shearing forces and bending moments, at the ends of the plates, that is, the end fault boundaries. Ratios that take into account the presence of different variants of the mentioned boundary conditions on the banks of the faults were built, and their effect on an earthquake possibility was studied.