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Title: Induced seismicity and style of deformation at Nurek reservoir, Tadjik SSR

Journal Article · · J. Geophys. Res.; (United States)

Induced seismicity is occurring at the 315-m high Nurek dam in Tadjikistan, USSR. An intense burst of seismicity accompanied the second burst of seismicity accompanied the second stage of filling of the reservoir from 120 to 200 m during August to December 1976. Hypo-central locations and fault plane solutions determined using data from a 10-station telemetered network surrounding the reservoir show the activity to be concentrated on a series of narrow, planar fault zones near the central basin and on more diffuse zones along the upstream edges of the reservoir. The activtiy extends to depths of 8 km and appears to be confined within the upper plate of the Ionakhsh thrust, a listric fault which outcrops 1 km north of the dam. The dominant mode of deformation in the post-Paleozoic sediments of the Tadjik Depression is thrusting. Fault plane solutions for the induced seismicity show short segments of strike slip and thrust faulting for the most intense activity near the central basin and normal and thrust faulting along the upstream edges of the reservoir. None of the fault zones delineated by the induced seimicity corresponds to faults mapped at the surface, while none of the surface faults mapped in the reservoir area has shown an increase in seismicity. The spatial distribution of seismicity within the active zones is in general agreement with that expected from models of the changes in strength associated with reservoir loading. The temporal distrubition of seismicity shows a migration outward from the center of the reservoir, probably associated with diffusion of pore pressure.

Research Organization:
Lamont-Dohery Geological Observatory of Columbia University, Palisades, New York 10964
Journal Information:
J. Geophys. Res.; (United States), Vol. 87:B6
Country of Publication:
United States