Structural and seismic indications of the elements of recent and present-day stress fields in several epicentral regions of western Tien Shan
Abstract
This study presents the results of stress field reconstruction for the epicentral zones of large-magnitude earthquakes in some folded-mountain regions of western Tien Shan. Field studies, including geostructural and tectonophysical interpretations, performed for the Talas-Suusamyr, Chatkal-Kurama, Turkestan-Zarafshan, Gissar and Nurata-Kyzylkum regions allow the reconstruction of some regional components of the tectonic stress field. The nearly E-W orientations of the lower-order compressional axes are identified in the Chatkal-Kurama and Turkestan-Zarafshan mountain areas. Detailed structural-dynamical diagrams of several epicentral zones and reconstructions of focal mechanisms of some strong earthquakes are derived from the geostructural data. The coincidence of the present-day stress field manifested in the earthquake sources and the recent stress field derived from the geostructural determinations is revealed. The focal mechanisms of the strong earthquakes in the folded-mountain regions of western Tien Shan relate to the thrust/strike-slip faulting and breakup of large tectonic blocks.