Seismic observations in the geodynamic proving at the Sayano-Shushenskaya HPP

Abstract

Results of seismic observations of the dam indicated that its resonance vibrations do not correspond to the basic operating frequency of the generating sets.According to a seismic-zoning map [21], the area surrounding the Sayano-Shushenskaya hydroproject falls within zones of 7 -10-point tremors. Considering seismological research [15,22], the location of the dam is classed as an 8-point intensity zone.The reservoir behind the Sayano-Shushenskaya Hydroelectric plant (SSHPP) is situated in a region where two large-scale structures of the folded Altay-Sayan region merge: the deeply folded West-Sayan uplift and the Tuva inter-mountain depression. The geology of the region where the SSHPP resides is characterized by the existence of a very broad range of structures: from regional structures with an expanse in the hundreds of kilometers to higher-order structures measured in several kilometers. The dam behind the SSHPP is located at the center of the long, narrow (30 -40 km) anticlinorium Dzhbashskii block of recent proterozoids, which is framed by early paleozoids. The complexes of these deposits are broken-through by middle Paleozoic granitoids and gabbroids. The northern boundary of the block passes along the North-Sayan regional fold, and the southern boundary along the Borusskaya fault. The boundary of the mountainous structure of the Western Sayan and the Minusinsk trench passes along the deep Minusinsk fault 35 -40 km north of the dam. The Kantegirka regional fault passes 30 km to the south of the dam. Of the enumerated faults, only the Borusskaya lies within 15 km to the south of the dam, and part of ist subparallel northern branch shows a clearly expressed face of the latest activation. A decipherable virgin seam of the fault can be distinctly traced over a distance of 40 km [22]. According to results of geologic-geophysical investigations, a complex system of faults that are branching outward from the regional faults are also observed below the body of the Sayano-Shushenskaya Dam.Seismological observations of the area are divided into two periods: pre-instrument, and instrument. The first includes archival information [8,17]. The second can be subdivided into the following three stages:-first, predesign -determination of the "stated" intensity of tremors in the area of the hydroproject, which has been made by field detachments of the Institute of Physics of the Earth;-second -continuous regime seismological observations in the Altay-Sayan region, which were begun in 1962 by the Siberian Division of the Russian Academy of Sciences, and the surrounding area of the modern proving ground at the SSHPP; and, -third -local observations in the region of the Sayano-Shushenskaya hydroproject, which were begun in 1990 in conformity with design documentation for construction of the SSHPP on the initiative and support of V. I. Bryzgalov the General Director of the SSHPP at that time.The decision to create a proving ground for geodynamic observations in the area of the Sayano-Shushenskaya hydroproject was made by the RAO ...