The system of neotectonic faults in southeastern Altai: orientations and geometry of motion

Abstract

The implications of recent seismological and resistivity data for the geometry and orientations of neotectonic faults are generally consistent with the morphotectonic model of Gorny Altai as an area of crustal failure at the junction of two relatively stable blocks. The model predicts motions under general NW compression mainly on right-lateral strike-slip faults accompanied by systems of pinnate reverse and extensional faults. The locations and mechanisms of aftershocks that followed the 2003 Chuya earthquake (Gorny Altai) indicate long seismic activity generated by a neotectonic NW right-lateral strike-slip fault which separates the North Chuya and South Chuya ranges from the Kurai-Chuya system of intermontane basins. The plane of the northwestern termination of the active fault zone dips in the SE direction, beneath the ranges, at about 70°. MT data show two types of conductors that reach the surface, namely, nearly vertical zones along neotectonic faults between the blocks not involved into vertical motion, according to morphotectonic evidence, and inclined zones between the uplifted (subsided) blocks. We interpret the former as strike-slip faults and the latter as reverse or reverse oblique faults, which always dip beneath the uplifted blocks and record the general compressional setting.