Internal stress in block media as a factor responsible for interface strain activity. Estimation of excess tectonic stress

The paper studies the mechanisms of strain localization at the interfaces of structural elements in quasi-2D block-structured (plate) systems. The model plate system is the ice cover of the Lake Baikal. The emphasis in the paper is on analyzing the relationship between intraplate strains and interplate displacements. It is shown that the activation of convergent interplate displacements and the development of subduction zones in the ice cover are due to an increase in tensile intraplate stress, and this is consistent with the main mechanisms of tectonic processes in the lithosphere. Analysis of the stress distribution allows the conclusion that the deformation mechanisms in the block-structured ice cover fit the concept of plate tectonics. The obtained results make it possible to estimate the characteristic tectonic stress (2–10% of the plate strength) at which convergent interplate displacements are activated. It is found that in individual regions of the plate system, anomalously high internal stress (up to 20–30% of the plate strength) can be reached resulting in fragmentation of structural blocks and involvement of the thus formed interfaces in deformation. It is demonstrated that with the so high internal stress, the deformation at the interplate boundaries is far from typical, and this can be considered as a precursor of coming dynamic seismogenic events.