TECTONOPHYSICS OF THE ANGARA FAULT ZONE (SOUTHERN SIBERIAN PLATFORM)

Abstract

The Angara fault zone that extends from the Baikal Rift into the Siberian Platform through the most densely populated regions of Siberia has been investigated using geological and structural data. A database including 243 sites of mass measurements of faults and joints has been compiled for the region of the Irkutsk reservoir and the city of Irkutsk. A tectonophysical analysis showed that the Angara fault is expressed on the surface as a broad zone in which the sedimentary cover is cut into triangular, quadrangular, and pentagonal plate-shaped fault blocks. The shallow crust structure in the region formed in three major stages of tectonic activity of various styles in response to deformation in the neighboring Sayan-Baikal mobile belt. During the latest stage of activity, intense motions occurred on the Angara fault within the rift as well as along its subsidiary fractures on the craton (region of Irkutsk). Therefore, the existing construction engineering standards call for reassessment.