A Ground-Motion Prediction Equation for Fennoscandian Nuclear Installations

Abstract

We propose a ground-motion prediction equation (GMPE) for probabilistic seismic hazard analysis of nuclear installations in Finland. We collected and archived the acceleration recordings of 77 earthquakes from seismic stations on very hard rock (VHR, i.e., the shear-wave velocity in the upper 30 m of the geological profile=2800 m/s according to the definition used in the nuclear industry) in Finland and Sweden since 2006 and computed the corresponding response spectra important for engineering evaluation. We augmented the narrow magnitude range of the local data by a subset of VHR recordings of 33 earthquakes from the Next Generation Attenuation for Central and Eastern North America (CENA) (NGA-East) database, mainly from eastern Canada. We adapted the backbone curves of the G16 equation proposed by Graizer (2016) for CENA. After the calibration, we evaluated the accuracy of the median prediction and the random error. We conclude that the GMPE developed can be used for predicting ground motions in Fennoscandia. Because of compatibility with the original G16 backbone curve and comparisons with the NGA-East GMPEs, we estimate that the formulation proposed is valid on VHR over the range of 2≤moment magnitude≤7.0 and 0≤ rupture distance ≤300 km, the depth range over 1.5–37 km, and frequencies between 1 and 100 Hz. The median of the composite prediction of the GMPE proposed was reasonable. The standard deviation of the prediction error (σ) was over the range of 0.73–0.86, in ln spectral acceleration units, for the relevant spectral frequencies. This is somewhat lower than the G16 σ, indicating lower aleatory variability. The new Fenno-G16 GMPE is applicable over a wider range of magnitudes than the two older GMPEs available in Finland and fits the data better, especially for peak ground acceleration and 25 Hz.

Application of a Hybrid Modeling Method for Generating Synthetic Ground Motions in Fennoscandia, Northern Europe

“…The anelastic attenuation filter, based on Q, has been used in the G16 GMPE, with the value of Q0=650 (Graizer, 2016). This was raised to Q0=991.64 for the FennoG16 GMPE (Fülöp et al, 2020), based on comparisons with Fennoscandian data. Atkinson (2004a) calculated, at 1.0 Hz, Q0 =893 and c=0.32, quite similar value to the 991.64 for Q0 in FennoG16 (Fülöp et al, 2020).…”

A ground motion logic tree for seismic hazard analysis in the stable cratonic region of Europe: regionalisation, model selection and development of a scaled backbone approach

“…At periods longer than 0.3 s (for small magnitude and short distances) to 1.0 s (for larger magnitudes and longer distances) the centre and range of the distributions are similar, however. Also shown for comparison are the spectra from the recent GMM of Fülöp et al (2020), which adjusts the NGA East GMM of Graizer (2016) for application to the very hard rock sites ( V S 2800 m/s) in Finland using a dataset of strong motion records from small magnitude earthquakes in the region combined with response spectra from the original NGA East database. As the local calibration of model is made on the basis of seismicity mostly below the minimum magnitude considered for the ESHM20 ( M W ≥ 3.5 ) we do not use this as a "seed model" in the following analysis; however, it does form a useful point of comparison as it would seem to predict short period motions that are toward the upper end of the range indicated by the full NGA East model suite.…”

“…In Fig. 5, the ground motions from the Fülöp et al (2020) model are adjusted to the V S30 800 m/s reference rock using the same model of Stewart et al (2020). We note that at the time of writing very few of outcomes of the NGA East project themselves have been published in peer-reviewed scientific literature.…”

“…The final decision to assign the 0.8 weighting to the parametric model branches is based on an analysis of a small set of ground motion records from hard-rock ( V S 2800 m/s) sites Change in mean seismic hazard (solid lines) and 16th to 84th percentiles for the 475 year (left) and 2475 year (right) return period when changing the weight assigned to the new parametric craton model branch set in the logic tree from low-magnitude earthquakes ( 3.0 ≤ M L ≤ 4.1 ) in Fennoscandia. This dataset is published as an electronic supplement to Fülöp et al (2020) and though we believe it is insufficient to assist in the calibration of the GMM itself, it may be a deciding factor in final weighting decision. Comparing the fit of the 13 different GMM branches to this small dataset using log-likelihood approach and corresponding weighting scheme of Scherbaum et al (2009), we find that the total sum of the parametric logic tree branches is close to 0.8 at short-to-moderate periods (T < 0.5 s).…”

The Finnish National Seismic Network: Toward Fully Automated Analysis of Low-Magnitude Seismic Events

“…In addition, a local network of eight stations has been installed to monitor the site of a possible future nuclear power plant in Ostrobothnia, according to regulations of the International Atomic Energy Agency (Vuorinen et al, 2019). Data from the Ostrobothnian deployment have been important for developing a ground-motion prediction equation for Fennoscandia (Fülöp et al, 2020). The areas of notable seismic interest as well as earthquakes of ML0.0 and greater are plotted in Figure 1, along with permanent seismic stations in Finland.…”