Reconstruction of the Parameters of Shear Stresses during the Formation of Multirank Faults in the Western Baikal Region Based on Tectonophysical Interpretation of Lineaments

Abstract—The authors’ software made it possible to perform a detailed identification of lineaments at various scale levels for the region of the Obruchev fault system of the western Baikal region. The identified lineaments significantly complement the mapped framework of faults and are consistent with the strike of fault structures of the corresponding rank. Based on the analysis of the relative specific density of lineaments of the local scale level, reflecting en echelon megafractures of large faults, heterogeneous damage zones of regional structures were established, which were divided into relatively homogeneous segments. For each identified segment and each structure as a whole, using the developed software Lineament Stress Calculator, a reconstruction of shear stress parameters was carried out on the basis of P.L. Hancock’s model. It has been proved earlier that the main features of the Early Paleozoic stage of the region development during accretion of the Olkhon terrane to the southern margin of the Siberian Craton were accompanied by activation of right-lateral strike-slip displacements along the SW–NE accretionary sutures and active metamorphism processes. The results confirm that the main faults of the SW–NE strike, subparallel to the marginal suture of the Siberian Platform, formed at the early stage of their development as right-lateral strike-slips with orientation of the compression axis of ≈90°. Second-order faults of the NW–SE orientation are defined as left-lateral strike-slips and were probably formed at that time as antithetical shears in relation to the main structures, having received their development during further structural rearrangements of the region.