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European Geosciences Union, General Assembly 2014 Vienna, Austria, 27 April – 02 May 2014. A NEW EARTHQUAKE CATALOGUE FOR SEISMIC HAZARD ASSESSMENT OF THE NPP (NUCLEAR POWER PLANT) JASLOVSKE BOHUNICE, SLOVAKIA, SITE

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European Geosciences Union, General Assembly 2014

Vienna, Austria, 27 April – 02 May 2014

A NEW EARTHQUAKE CATALOGUE FOR SEISMIC HAZARD ASSESSMENTOF THE NPP (NUCLEAR POWER PLANT) JASLOVSKE BOHUNICE, SLOVAKIA, SITE

Kysel1,2, R., Kristek1,2, J. , Moczo1,2, P., Csicsay2, K., Cipciar2,1, A., Srbecky2, M.

1 - Comenius University in Bratislava, Slovakia 2 – Slovak Academy of Sciences, Bratislava, Slovakia

For declustering we applied two independent methods. In the window method we applied parameters of the time-space windows proposed by Burkhard & Grünthal (2009). In the cluster method (Reasenberg 1985) we applied alternative sets of input parameters.

For investigating time completeness we divided the catalogue into four subcatalogues corresponding to different seismogeological domains. The completeness was determined from the plots displaying cumulative number of events (for given subcatalogue and interval of magnitude) as a function of time.

The homogenized catalogue consists of 2 652 earthquakes with moment magnitude larger than 1.5.

The catalogue was subsequently used as an input source for hazard analysis.

According to the IAEA (International Atomic Energy Agency) Safety Guide No. SSG-9, an earthquake catalogue should comprise all information on pre-historical, historical and seismometrically recorded earthquakes in the region which should cover geographic area not smaller than a circle with radius of 300 km around the site.

JaslovskeBohunice is an important economic site. Several nuclear facilities are located in JaslovskeBohunice – either in operation (NPP V2, national radioactive waste repository) or in decommissioning (NPP A1, NPP V1). Moreover, a new reactor unit is being planned for the site.

JaslovskeBohunice site is not far from the Dobra Voda seismic source zone which has been the most active seismic zone at territory of Slovakia since the beginning of 20th century. Relatively small distances to Austria, Hungary, Czech Republic and Slovak capital Bratislava make the site a prominent priority in terms of seismic hazard assessment.

Abstract

Introduction

We compiled a new earthquake catalogue for the NPP JaslovskeBohunice region following the recommendations of the IAEA Safety Guide. The region includes parts of the territories of Slovakia, Hungary, Austria, the Czech Republic and Poland, and it partly extends up to Germany, Slovenia, Croatia and Serbia. The catalogue is based on data from six national earthquake catalogues, two regional earthquake catalogues (ACORN, CENEC) and a catalogue from the local NPP network.

The primarily compiled catalogue for the time period 350 – 2011 consists of 9 142 events. For homogenization, we divided the catalogue into pres-eismometric (350 – 1900) and seismometric(1901-2011) periods. For earthquakes characterized by the epicentral intensity and local magnitude we adopted relations proposed for homogenization of the CENEC catalogue (Grünthal et al. 2009). Instead of assuming the equivalency between local magnitudes reported by the national agencies, we analysed and estimated relations between them.

The seismological and geological databases comprise input data for probabilistic analysisof seismic hazard characteristics for the NPP site.

Information on pre-historical, historical and seismometrically recordedearthquakes in the Region are collected and documentedaccording to the IAEA Safety Guide No. SSG-9 (IAEA 2010).

The Safety Guide distinguishes Region and Near Region.

In compilation of the seismological databasefor the NPP JaslovskeBohunice Region we selected a symmetric area with radius of 305 kmand for the Near Region

a symmetric area with radius of 30 km from the site.

The NPP JaslovskeBohunice Region includes parts of the territories of Slovakia, Hungary, Austria, the Czech Republic and Poland, and partly extends up to Germany, Slovenia, Croatia and Serbia.

Inputs

Homogenization

Declustering

  • In compiling the seismological database, the so-called national catalogues,
  • bulletins (yearbooks) of national seismological agencies, regional catalogues
  • and global databases of earthquakes (e.g. ISC catalogue) were used.
  • After merging individual source catalogues,duplicate entries were removed based on following principles:
  • in case of identical time and localization data, only a primary entry was kept,
  • in case of dissimilar data, priority was given to data from the source catalogue
  • for the territory where earthquake was located.
  • The compiled seismological database contains data on 9 142 earthquakes that
  • were macroseismically felt and/or seismometrically recorded in the NPP Region:
  • 1 160 earthquakes do not contain information on the epicentral intensity or magnitude,
  • 7 982 earthquakes contain information on the epicentral intensity or type of magnitude.

The compiled seismological database was homogenized for a single quantity determining the earthquake size - the moment magnitude Mw.

  • Two independent methods for catalogue declustering were used:
  • A. Window method
  • The parameters of the time-space window were selected based on the Burkhard & Grünthal (2009):
  • time window for foreshocks [days] :
  • time window for aftershocks [days] :
  • space window [km] :
  • B. Cluster method
  • In the CLUSTER programme (Reasenberg 1985),
  • the following parameters were selected:
  • Tmin = 5 760 Tmax= 28 800 P = 0.99 xeff = 1.5 xk = 0.5 rfact = 15.0
  • A. Preseismometric period (350 – 1900)
  • I0 → Mw
  • The epicentral intensity distribution I0 for 1 226 earthquakes is shown in the table.
  • For the I0 to Mw conversion, two alternative relations were used following the homogenization procedure of the CENEC catalogue (Grünthal et al. 2009):
  • in case of information on focal depth h :
  • in case of no information on focal depth h :
  • 386 earthquakes with I0 ≥ 4.5were homogenized.

B. Seismometric period (1900 – 2011)

I. Mw

moment magnitudes for 39 earthquakes were simply adopted

II. mb → Mw

ISC/NEIC body-wave magnitudes for 33 earthquakes were converted by the Scordilis (2006) relation:

Period 1901 - 1984 Period 1985 – 2011

III. ML → Mw

1st step:ML national → ML ZAMG

2nd step: ML ZAMG → Mw

for 1 473 earthquakes with ML ZAMG≥ 1.5, Grünthal (2009) relations was adopted:

IV. I0 → Mw

212 earthquakes with I0 ≥ 4.5were homogenized under the procedure described in part A.

III. I0 → Mw

591 earthquakes with I0 ≥ 4.5

were homogenized under the procedure described in part A.

IV. ML/MS → Mw

local magnitudes and surface wave magnitudes for 110 earthquakes were assumed equivalent to moment magnitude

Completeness

The completenessin time was analysed from the plots displaying cumulative number of events for given seismogeological domain and given magnitude interval and for some cases the completeness was expertly judged.

Summary on thehomogenized database

Minimum moment magnitude Mw: 1.5

Number of earthquakes: 2 652

For the purpose of further processing of the database, the homogenized seismological database was namedthe„catalogue“.

Conclusions

  • We compiled a new earthquake catalogue for the NPP JaslovskeBohunice region following the recommendations of the IAEA Safety Guide.
  • The homogenized catalogue contains 2652 entries with moment magnitude greater than 1.5.
  • The completeness analysis was done for four seismological domains.
  • Two methods of declustering were applied.
  • The catalogue was subsequently used as an input for theseismic hazard analysis of the NPP JaslovskeBohunice site.

Grünthal, Wahlström, Stromeyer, 2009. The unified catalogue of earthquakes in central, northern, and northwestern Europe (CENEC) – updated and expanded to the last millennium.J. Seismol. 13, 517-541.

IAEA, 2010. Seismic Hazards in Site Evaluation for Nuclear Installations. Specific Safety Guide No. SSG-9. IAEA, Vienna.

Burkhard, Grünthal, 2009. Seismic source zone characterization for the seismic hazard assessment project PEGASOS by the Expert Group 2 (EG 1b). Swiss J Geosci 102, 149-188.

Reasenberg, 1985. Second-Order Moment of Central California Seismicity, 1969-1982. J. of Geophys. Res. 90, 5479-5495.

Scordilis, 2006. Empirical global relations converting MS and mb to moment magnitude. J. Seismol. 10, 225-236.

Acknowledgements This work was supported in part by the Slovak Research and Development Agency under the contract No. SK-GR-0032-11 (Slovak – Greek bilateral project). We also gratefully acknowledge the funding by the JESS, a.s. through the „Assessment of the Seismicity and Geological Conditions for the NNPP EBO Project“.