ESTIMATION OF SEISMIC HAZARD ON A PROSPECTIVE NPP SITE IN SOUTHERN FINLAND

Transcription

1 ESTIMATION OF SEISMIC HAZARD ON A PROSPECTIVE NPP SITE IN SOUTHERN FINLAND Presentation in CSNI workshop SEISMIC INPUT MOTIONS, INCORPORATING RECENT GEOLOGICAL STUDIES TSUKUBA, November 2004 by Pentti Varpasuo* Fortum Nuclear Services Ltd Rajatorpantie 8, Vantaa, Fortum pentti.varpasuo@fortum.com Fortum CSNI Workshop, Tsukuba, Japan

2 1 Introduction The purpose of the present work is the estimation of seismic hazard in the territory of the prospective nuclear power plant site in Southern Finland. Because there are no registered strong motion acceleration recordings of earthquakes in Finland, the earthquake recordings from Saguenay and Newcastle regions from Canada and Australia were taken as sources of initial data because of their geological and tectonical similarity to Fennoscandia. The probabilistic seismic hazard assessment consists of three parts: 1) source effects, 2) path effects, 3) site effects. Fortum CSNI Workshop, Tsukuba, Japan

3 2 Regional seismicity in Fennoscandia Figure 1 shows that southern Finland, which is the target area of this study, is characterised by relatively low seismicity. The most active belts of seismicity close to it are the Swedish coast from the Bothnian Sea to the Bothnian Bay, western Lapland and the northern Bothnian Bay- Kuusamo region. Southern Finland and areas south and east of it are characterised generally by a lower seismic activity. However, two NW- SE oriented belts of relatively high seismic activity run through the region. The northern zone of higher activity runs from the southern Bothnian Bay towards Ladoga (B-L). The other active belt (Å-P-P) runs from the Åland archipelago to southeastern Estonia, where it extends to from Paldis to Pskov. Fortum CSNI Workshop, Tsukuba, Japan

4 E en tat ion :0 Bo rde ro f th ep res 70 N Lapland Kuusamo SWEDEN 65 N BB Oulujärvi FINLAND RUSSIA Bothnian Sea 60 N 200 km M = 4.5- ESTONIA M = - M = - 25 E 20 E 30 E M = - 55 N Figure 1: Distribution of the earthquake epicenters in northern Europe since 1375 according to FENCAT. Fortum CSNI Workshop, Tsukuba, Japan

5 3 Division of the source area to source zones The annual event rates are used directly for seismic hazard analysis, as well the greatest magnitudes registered in the used catalogue for each source zone. Each zone was divided into sub-zones, each of which in its turn represents the quadrilateral area (e.g.... in Figure 2). The vertices of these quadrilateral areas are given with global longitudinal and latitudinal coordinates. These coordinates formed the geometrical initial data for the analysis done by the program SEISRISK III. Fortum CSNI Workshop, Tsukuba, Japan

6 Fortum CSNI Workshop, Tsukuba, Japan km Hästholmen Hästholmen Hästholmen Hästholmen Hästholmen Hästholmen Hästholmen Hästholmen Hästholmen M=- 500 km M=- M=- M=- M=- M=- M=- M=- M=- M=- M=- M= Earthquakes: ( ) Figure 2. The source zone division for the Loviisa site embedded on the Fennoscandian epicentral map

7 Fortum CSNI Workshop, Tsukuba, Japan km Olkiluoto Olkiluoto Olkiluoto Olkiluoto Olkiluoto Olkiluoto Olkiluoto Olkiluoto Olkiluoto M=4,5- M=1,5-2,4 M=2,5-3,4 M=3,5-4, ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) Earthquakes: Earthquakes: Earthquakes: Earthquakes: Earthquakes: Earthquakes: Earthquakes: Earthquakes: Earthquakes: Figure 3 The source zone division for Olkiluoto site embedded on the Fennoscandian epicentral map

8 4 Attenuation of ground acceleration In the following figures the attenuation relations for the logarithm of peak ground acceleration or various spectral accelerations are given as well as the attenuation for the peak ground acceleration ordinates. The figures are for longitudinal and transversal components of Saguenay and Newcastle strong motion records, which for the purposes of this study are regarded as independent recordings. For reliable determination of the coefficient c2 the magnitude data represented in combined Saguenay-Newcastle data set was too scarce. For that reason the c2 coefficient was determined on the basis of literature study. The attenuation curves of the records for the longitudinal component os Saguenay and Newcastle datasets are given next: Fortum CSNI Workshop, Tsukuba, Japan

9 Figure 4 Spectral attenuation fit for Saguenay longitudinal component. Damping 5%. Magnitude 5.8 Fortum CSNI Workshop, Tsukuba, Japan

10 Figure 5 Spectral attenuation fit for Newcastle longitudinal component. Damping 5%. Magnitude 5.8 Fortum CSNI Workshop, Tsukuba, Japan

11 5 Decision tree for the treatment of uncertainties The code basis for the ground motion estimation in probabilistic seismic hazard studies stipulates the median spectra for mean return period of years. The decision three used in the treatment of uncertainties in this study was as follows. Fortum CSNI Workshop, Tsukuba, Japan

12 D E S I G N L O V I I S A a,b by sources (0.6) observed max. magn (0.5) observed max. magn (0.5) SAGUENAY LONGITUDINAL(0.3) SAGUENAY TRANSVERSAL(0.3) NEWCASTLE LONGITUDINAL(0.2) NEWCASTLE TRANSVERSAL(0.2) SAGUENAY LONGITUDINAL(0.3) SAGUENAY TRANSVERSAL(0.3) NEWCASTLE LONGITUDINAL(0.2) NEWCASTLE TRANSVERSAL(0.2) G R O U N D M O T I O N C A T A L O G (0.5) O L K I L U O T O C A T A L O G (0.5) a,b by catalogs (0.4) a,b by sources (0.6) a,b by catalogs (0.4) observed max. magn (0.5) observed max. magn (0.5) observed max. magn (0.5) observed max. magn (0.5) observed max. magn (0.5) observed max. magn (0.5) SAGUENAY LONGITUDINAL(0.3) SAGUENAY TRANSVERSAL(0.3) NEWCASTLE LONGITUDINAL(0.2) NEWCASTL E TRANSVERSAL(0.2) SAGUENAY LONGITUDINAL(0.3) SAGUENAY TRANSVERSAL(0.3) NEWCASTLE LONGITUDINAL(0.2) NEWCASTL E TRANSVERSAL(0.2) SAGUENAY LONGITUDINAL(0.3) SAGUENAY TRANSVERSAL(0.3) NEWCASTLE LONGITUDINAL(0.2) NEWCASTL E TRANSVERSAL(0.2) SAGUENAY LONGITUDINAL(0.3) SAGUENAY TRANSVERSAL(0.3) NEWCASTLE LONGITUDINAL(0.2) NEWCASTL E TRANSVERSAL(0.2) SAGUENAY LONGITUDINAL(0.3) SAGUENAY TRANSVERSAL(0.3) NEWCASTLE LONGITUDINAL(0.2) NEWCASTL E TRANSVERSAL(0.2) SAGUENAY LONGITUDINAL(0.3) SAGUENAY TRANSVERSAL(0.3) NEWCASTLE LONGITUDINAL(0.2) NEWCASTL E TRANSVERSAL(0.2) Figure 6 Logic three structure for treating uncertaint ies Fortum CSNI Workshop, Tsukuba, Japan

13 6 Results By preparing the initial data according to the previous section, the further analysis was carried out on Fortran Computer Program for Seismic Hazard Estimation SEISRISK III developed by Bender and Perkins in USGS. The resulting raw site hazard curves are given in following Figure 7 and the medion hazard curve with 5% and 95% fractiles are shown in Figure 8. Fortum CSNI Workshop, Tsukuba, Japan

14 Olkiluoto3 raw seismic hazard curves in PGA; Seisrisk II analysis 1.E-01 Annual frequency of exceedance 1.E-02 1.E-03 1.E-04 1.E-05 1.E-06 1.E-07 1.E-08 1.E-09 1.E PGA amplitude (g) L0_1ln L0_1ls L0_1tn L0_1ts L0_1Rln L0_1Rls L0_1Rtn L0_1Rts L0_5ln L0_5ls L0_5tn L0_5ts L0_5Rln L0_5Rls L0_5Rtn L0_5Rts O0_1ln O0_1ls O0_1tn O0_1ts O0_1Rln O0_1Rls O0_1Rtn O0_1Rts O0_5ln O0_5ls O0_5tn O0_5ts O0_5Rln O0_5Rls O0_5Rtn O0_5Rts Figure 7. Seismic Hazard in PGA for the prospective site in form the 32 raw hazard curves Fortum CSNI Workshop, Tsukuba, Japan

15 Distribution of hazard curves for Olkiluoto site; Seisrisk II analysis 1.E-02 1.E-03 Annual frequency of exceedance 1.E-04 1.E-05 1.E-06 1.E-07 1.E-08 1.E-09 1.E PGA amplitude (g) 5%fractile median 95%fractile Figure 8. Hazard curves with confidence bounds (5%, median, 95%) for prospective site Fortum CSNI Workshop, Tsukuba, Japan

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20 [ 20] Branch, M.A., Grace, A Optimization Toolbox, for use with Matlab. [21 ] McCue, K., Dent, V. and Jones T. The characteristics of Australian strong ground motion. Pacific Conference on Earthquake Engineering, Australia, Nov. 1995: [22 ] Sinadinovski, C., McCue K. F., Somerville M. Strong ground motion simulation of Australian intra-plate earthquakes, 17th European Conference on Earthquake Engineering, 1998, Balkema, Rotterdam. [ 23] Xu J.,Philippacopoulas A. J., Miller, C. A., Constantino C. J., Cares (Computer Analysis for Rapid Evaluation of Structures 1.0, NUREG/CR-5588,BNL-NUREG-52241,Vol. 1-3, Brookhaven National Laboratory, May Fortum CSNI Workshop, Tsukuba, Japan

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