by Pentti Varpasuo* Fortum Nuclear Services Ltd Rajatorpantie 8, Vantaa, Fortum

Transcription

1 THE INFORMATION REPORT OF EARTHQUAKES IN NORTHWEST OF RUSSIA CLOSE TO THE CITY OF KALININGRAD ON SEPTEMBER 21, 2004 AND THE ASSESSMENT OF THEIR EFFECTS AT OL3 NPP SITE by Pentti Varpasuo* Fortum Nuclear Services Ltd Rajatorpantie 8, Vantaa, Fortum Fortum CSNI Workshop, Tsukuba, Japan

2 1 Introduction On September 21, 2004 in northwest Russia close the city of Kaliningrad a series of earthquakes occurred, with maximum magnitude of the main shock (Ms=4.3) at 13:32 minutes in Greenwich time. It was preceded with earthquake with magnitude of Ms=4.0 at 11:05 minutes of the Greenwich time. Weaker subsequent push is registered also at 13:36 minutes of Greenwich time. Two first earthquakes were felt in territory of the Kaliningrad area and in the adjoining areas of Belarus, the Baltic states, in northern areas of Poland and in the south of Finland. Fortum CSNI Workshop, Tsukuba, Japan

3 2 THE BULLETIN OF THE RUSSIAN ACADEMY OF SCIENCES The Kaliningrad earthquake is registered by all stations of the Institute of Geophysics of the Polish Academy of Sciences. The station of this network located nearest to the epicentre is Suwalki (SUW). The Suwalki and Vasula records are available in the EMCS data bank Wilber II. In addition to the above records available in the analysis of Russian Academy of Sciences the Kaliningrad event has been registered by Petrozavodsk of Institute of Geology of the Karelian Centre of Science of the Russian Academy of Science. The Petrosavodsk records have also been transferred to Obninsk and used at the determination of hypocenter locations of Kaliningrad earthquakes by Russian Academy of Science. In Figure 1 fragments of the seismogram records of the first earthquake at 11:05 minutes from 4 digital stations accessible to Academy of Sciences of Russian Federation are depicted. In Figure 2 fragments of seismogram records of the same digital stations for the main shock at 13:32 minutes are submitted. Fortum CSNI Workshop, Tsukuba, Japan

4 Figure 1: The registrations of VSU, KHC, PUL and OBN stations of the BHZ component of the 11:05 event. Fortum CSNI Workshop, Tsukuba, Japan

5 Figure 2 The registrations of VSU, KHC, PUL and OBN stations of the BHZ component of the 11:32 event Fortum CSNI Workshop, Tsukuba, Japan

6 3 THE BULLETIN OF THE UPPSALA UNIVERSITY The web site of the Uppsala University gave the eeismograms of the both events in Kaliningrad registered at Byxelkrok, Oskarshamn and Vastervik stations for three perpendicular displacement components BHN, BHE and BHZ. The university web site gave also the data in compressed, digital form but during the short time frame allocated to this investigation it was not possible to convert these records to ASCII format. In the following Figure 3 is given the seismogram record of the Oskarshamn station for the Kaliningrad main shock at 13:32. Fortum CSNI Workshop, Tsukuba, Japan

7 Figure 3. The seismogram record for Kaliningrad main event at 13:32 in Oskarshamn station Fortum CSNI Workshop, Tsukuba, Japan

8 4 THE INSTITUTE OF SEISMOLOGY OF UNIVERSITY OF HELSINKI INFORMATION BULLETIN The Institute of Seismology of Helsinki University provided the records of two stations for this investgation. The records were the three component seismograms at stations of Virolahti and Kevo. The locations of these stations are shown in the map of Figure 4. The obtained digital records were differentiated numerically twice to obtain the acceleration records. In the following two Figures 5 and 6 the BHN component acceleration record is given for the Kaliningrad main event at Virolahti and at Kevo: Fortum CSNI Workshop, Tsukuba, Japan

9 Figure 4 Locations of Finnish seismogram stations Fortum CSNI Workshop, Tsukuba, Japan

10 FI_VJF_BHN_COMPONENT_ACC acc m/s/s seconds Figure 5. The Kaliningrad main event. Virolahti acceleration record for BHN component Fortum CSNI Workshop, Tsukuba, Japan

11 FI_KEV_BHN_COMPONENT_ACC acc m/s/s seconds Figure 6. The Kaliningrad main event. Kevo acceleration record for BHN component Fortum CSNI Workshop, Tsukuba, Japan

12 5 ORFEUS DATABANK INFORMATION Orfeus stands for Observatories and Research Facilities for European Seismology. ORFEUS is the European non-profit organisation that aims at coordinating and promoting digital, broad-band seismology in Europe. Orfeus located and sized the Kaliningrad earthquakes as follows: 1) Earthquake mb 4.4 close to the city of Ladushkin September 21st, 2004, 11:05 UTC; 2) Earthquake mb 5.0 close to the city of Primorsk September 21st, 2004, 13:32 UTC. The seismogram data in Orfeus is available for following stations that are depicted in Figure 7. Fortum CSNI Workshop, Tsukuba, Japan

13 Figure 7. The location map of the recording stations for the Kaliningrad quakes in Orfeus Fortum CSNI Workshop, Tsukuba, Japan

14 In the following two Figures 8 and 9 the acceleration time histories differentiated from German GEOFON records at Suwalki, and Vasula for BHN component are given in form of time histories. The length of the histories is about 5 minutes for each history and the time step is 0.05 seconds. The calibration coefficient in the seismograms is of the order of 1E+9, which means that the recorded values have to be divided by this coefficient in order to get ground displacements in meters. Fortum CSNI Workshop, Tsukuba, Japan

15 2 GE_SUW_BHN_COMPONENT_ACC acc m/s/s seconds Figure 8. The recorded acceleration time history at Suwalki station Fortum CSNI Workshop, Tsukuba, Japan

16 GE_VSU_BHN_COMPONENT_ACC acc m/s/s seconds Figure 9. The recorded acceleration time history at Vasula station Fortum CSNI Workshop, Tsukuba, Japan

17 6 PROCESSING OF THE COLLECTED DATA In order to assess the intensity of the ground shaking with various distances from the epicentre the acceleration response spectra for 5% damping were generated for Suwalki, Vasula and Virolahti records and for horizontal BHN component. To assess the hazard at Olkiluoto site the YVL 2.6 design ground spectrum was included in the same Figure 10. Fortum CSNI Workshop, Tsukuba, Japan

18 The effect of Kaliningrad quake at various distances and OL3 design spetrum YVL_2_6 1 Spectral acceleration (g) Frequency Hz Virolahti_N_comp Suwalki_N_comp Vasula_N_comp YVL_2_6 Figure 10. The recorder acceleration spectra and the OL3 design spectrum Fortum CSNI Workshop, Tsukuba, Japan

19 7 CONCLUSION As it can be seen from the Figure 10 the Kaliningrad event does not constitute significant seismic hazard at Olkiluoto site or at comparable distances from epicenter. Fortum CSNI Workshop, Tsukuba, Japan