SEISMIC HAZARD AND GROUND MOTION FOR LENINGRAD NPP SITE

摘要

The paper is part of the project Leningrad NPP In-depth Safety Analysis. The aim of the paper is to develop theseismic hazard curves and the spectral shape for the ground motion at LNPP site.The input data for the study consists of two earthquake catalogs and two sets of seismic ground motion recordings.The earthquake catalogs are FENCAT and FSU catalog. The first catalog is compiled and maintained by the Institute ofSeismology of Helsinki University for Fennoscandian region. The second catalog for the former Soviet - Union territory wascompiled by late professor Shebalin from Russian Academy of Sciences. The attenuation data used in the study was collectedfrom two intra-plate, moderate seismicity, pre-cambrian rock regions judged to be similar with target region. These regionswere Saguenay region from eastern Canada and Newcastle region from western Australia. The source effects characterizationwas done with the aid of Richter's a and b parameters calculated on the basis of epicenter locations and magnitudes given inthe FENCAT and FSU catalogs. The attenuation relationships presented in tabular form were developed on the basis of theequation form given by Dahle, Bungum and Kvamme. The coefficients in the attenuation relations for 10 different spectralfrequencies were calculated by non-linear regression.The hazard assessment methodology was standard approach utilizing Poisson process assumption of for earthquakeoccurrence. The investigated region was divided into separate source areas. The seismicity of sources was evaluated in termsof a and b parameters. Attenuation relatioships were determined and the seismic hazard in terms of spectral accelerationfrequencies for the site was determined.The last step of the analysis was the development of synthetic ground motion using the uniform hazard spectralshape developed in the first part of the study. The results of the hazard assessment were presented in the form of the hazardcurve in terms peak ground acceleration and in terms of uniform hazard spectral shape for the mean return period of onehundred thousand years. The synthetic ground motion was presented in the form two horizontal and one vertical accelerationtime histories fitted to match the uniform hazard response spectrum.