Structural and seismic evidence for intracontinental subduction in the Peter the First Range, central Asia

Examines the stratigraphy, structure, and seismicity of the Peter the First Range, Tadjikistan. The range represents a highly deformed segment of a large intracontinental basin, the Tadjik Depression, which is being shortened in response to the Cenozoic convergence between two orogenic massifs, the Pamir and the Tien Shan Ranges. The stratigraphy and structure of the region are best explained by a model of the Mesozoic Tadjik Depression as an intracontinental, foreland basin, developed in a back-arc position with respect to the active Andean or collisional orogens located in northern Afghanistan and the Pamir. Seismicity in the region is dominated by earthquakes extending from the surface to ~12-km depth, apparently occurring within the deformed sediments of the Peter the First Range. A subhorizontal zone of relatively low activity at this depth may mark the location of a basal detachment that underlies a structurally thickened sedimentary section. This aseismic zone is in turn underlain by a south-dipping belt of seismicity that extends from about 17- to 35-km depth, and which can be traced updip to the seismogenic crystalline basement of the Tien Shan range to the north. -from Authors