Home – Home – Jornals – Russian Geology and Geophysics 2018 number Неопубликованное

The junction zones of mountain ranges with sedimentary basins are concentrators of seismogenic faults that develop in settings of regional compression and transpression. The development of two opposing systems of reverse faults and thrusts forms positive (forbergs, “pop-up” structures, fault and tectonic scarps, fault related fold) and negative morphostructures (“pop-down” structures) at the edges of sedimentary basins. As a result, the edges of the basins are involved in uplift. This leads to a gradual growth and expansion of the mountain ranges and a reduction in the areas of intramountain basins, i.e. the reduction mechanism of the upper part of the earth's crust is realized. However, the mechanisms of the emergence of conjugate fault systems are not fully understood. The mechanisms of such deformations in the upper part of the earth's crust were investigated under lateral compression of the rock mass using two-dimensional numerical modeling. The elastic-plastic approximation of the Drucker-Prager-Nikolaevsky model with a non-associated flow law was used. In all models, regardless of the number of layers, reverse faults and thrusts with direct and reverse dips relative to the direction of horizontal compression were formed. As a result, positive and negative structures were formed in the relief of the models, which are analogs of the corresponding natural morphostructures. The obtained results showed that the development and configuration of localized shear bands corresponding to reverse faults and thrusts are influenced by elastic-strength properties, basal friction, and boundary conditions at the lateral boundaries of the model. It has been established that in a multilayer medium a multilayer system of localized shear bands can form because of one stage of deformations that have different slopes and are limited only to a specific layer. Special attention should be paid to models in which interlayer slippage develops. It is caused by different rates of layer displacement relative to each other due to differences in the elastic-strength properties of rocks, which leads to the development of reverse thrusts in the upper part of the section that are not associated with the base of the model. Typically, such thrusts develop in the upper part of the section. Heterogeneities in the base of the models, regardless of strength properties, can affect the spatial localization of localized shear bands that arise at their boundaries. The results of numerical modeling allowed us to better understand the relationship between the mechanical properties of rocks and sediments with the features of the development of reverse-thrust structures.