THE EPICENTRAL AREA OF THE CHUYA EARTHQUAKE (GORNY ALTAI): THREE-DIMENSIONAL VELOCITY STRUCTURE

Abstract

The three-dimensional velocity structure of upper crust in the epicentral area of the Chuya earthquake was imaged using traveltimes of P and S waves from aftershocks. The northeastern part of the area including the territory of the Chagan-Uzun block and the Kurai and Chuya intermontane basins corresponds to a zone of high P velocities and Poisson's ratios. The southwestern part is a zone of relatively low P velocities and Poisson's ratios within the North Chuya ridge. S velocities are rather uniformly distributed over the area and show no significant anomalies. The main shock and the aftershocks, which are aligned in the northwestern direction, originated at the edge of the revealed anomalous P velocity zone.