Seismotectonic Features of the Spatial Volumetric Structure of Faults Activated with Chuy Earthquake M s = 7·3 Occurred on September 27, 2003 in Mountain Altai (Russia): Results of the Study of the Upper-Crustal Focal Area
Data from a dense seismic network, long-term observations, and modern methods for locating the aftershock hypocenters of the Chuy earthquake in 2003 were used to compile a spatial volumetric seismic portrait of seismically activated faults. The results revealed a cup-shaped structure of the aftershock process with a maximum focal depth of ~20 km at the center of the aftershock region, the presence of uneven changes in density of the aftershock origins along the master strike-slip fault with weakening activity of the main shear zone at the sections of its intersection with faults. The width of the activated zone along the master fault varies from 12 km to 10 km, which can be explained by the variability of the zone of influence of the fault with distance. Variability of the slope of the activated master fault, related to the block structure of the epicentral region has been established. The feathering and branching plots on the master fault were identified and studied. Horizontal seismically activated layers extending laterally from the master fault were revealed. Two layers are located at depths of 1020 km. The first layer is under the ChaganUzun block; the second layer is under the northwestern edge of the Kurai depression. The third horizontal layer, at a depth of ~2 km, departs from the master fault to the North Chuy range.
