Empirical evaluation of the control period TC for intermediate-depth earthquakes: application for Romania

This study focuses on the empirical assessment of the control period T-C for intermediate-depth earthquakes. A ground motion database of about 700 recordings from 25 intermediate-depth seismic events occurring in the Vrancea seismic zone in Romania as well as in other sources in the world is used in the study. A simple empirical model is proposed for the evaluation of the control period T-C. The largest part of the variability of the proposed empirical model can be attributed to the intra-event component. The analysis of the residuals has shown no significant bias due to the different tectonic regimes of the earthquakes in the database. A comparison between the seismic hazard results in terms of T-C computed using the proposed empirical model and from spectral accelerations according to the procedure from the proposed Eurocode 8 draft is performed for several case study sites in Romania. The probabilistic seismic hazard assessment shows that the control periods T-C computed in this study are much larger than the ones obtained using the approach from the proposed Eurocode 8 draft revision and larger, as well, than the T-C values proposed in the current version of the Romanian seismic design code P100-1/2013. The study also shows that for Romania, a solution for the seismic hazard zonation is to perform the analysis of S-& alpha; according to the provisions from the proposed Eurocode 8 draft and to evaluate the control period T-C using an empirical model.