Deep faults are identified by us with lines or zones of disturbance of horizontal layering of rocks of the Earth's crust and upper mantle. Such disturbances in gravity survey are approximated by structures like vertical or steeply sloping ledge, and the location of the lateral edge of the ledge or fault zone is characterized by maximum horizontal gradients of gravity.

Seismic exploration by the method of reflected waves is successfully applied in the study of sedimentary rock structures. Here its results are characterized by high accuracy and it occupies a leading position among other geophysical methods. Similar studies by the method of reflected waves of the deep structure of crystalline rocks could give the same valuable results that have been obtained in the study of sedimentary formations. But so far, except for some experimental works, this method has not been practically applied to the study of crystalline rocks. Therefore, the results of experimental and then production works by the method of reflected waves, carried out by the Western Geophysical Trust in cooperation with the problem laboratory of geophysical methods of exploration at the Leningrad Mining Institute in the central regions of the Kola Peninsula in 1958-1960, are of great interest.

The Omsk syneclise is composed of Jurassic, Cretaceous and Tertiary sandy-clayey sediments. These are almost undislocated and non-metamorphosed sedimentary rocks with no effusive or intrusive formations. The thickness of sedimentary rocks lies on the eroded surface of the folded basement, which has a two-tiered structure in most of the territory of the syneclise. The upper tier is represented by effusive-sedimentary rocks, weakly dislocated and weakly metamorphosed, within which there are strata with different degrees of dislocation and separated by erosion surfaces. The rocks appear to be of Lower Jurassic to Devonian age. For example, in Barabinsk the structure of the upper tier of the basement is as follows. In the interval of 2215-2234 m lie tuffites, sandstones and mudstones of Lower Jurassic - Upper Triassic age with dip angles of 5-8°. Below, from the depth of 2234 m to the bottom of the well stopped at the depth of 2470 m, the rocks are argillites with thin interbeds of tuffogenic sandstones and tuffs. These layers are inclined at an angle of 45°. Initially, the age of the rocks, determined by spore analysis, was considered to be Upper Devonian, later it was considered to be simply Paleozoic.