Tectonophysics of the Angara fault zone (southern Siberian Platform)

The Angara fault zone that extends from the Baikal Rift into the Siberian P latform through the most densely populated regions of Siberian has been inv estigated using geological and structural data. A database including 243 si tes of mass measurements of faults and joints has been compiled for the reg ion of the Irkutsk reservoir and the city of Irkutsk. A tectonophysical ana lysis showed that the Angara fault is expressed on the surface as a broad z one in which the sedimentary cover is cut into triangular, quadrangular, an d 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. Dur ing the latest stage of activity, intense motions occurred on the Angara fa ult within the rift as well as along its subsidiary fractures on the craton (region of Irkutsk). Therefore, the existing construction engineering stan dards call for reassessment.