Analysis of exceedance probabilities for design spectral accelerations from crustal earthquakes in Romania

Abstract

The seismic hazard of the eastern and southern part of Romania is dominated by the Vrancea intermediate-depth seismic source, while for the western part of Romania the local crustal seismic sources are predominant. The design acceleration response spectrum of the Romanian seismic code is obtained by anchoring the design peak ground acceleration to a spectral shape which takes into account the soil conditions through the control period TC. In this study, we aim to evaluate the exceedance probabilities of the design spectral accelerations in the case of various low- and moderate-magnitude crustal earthquake scenarios. The evaluation is performed using an approach based on a ground motion prediction equation and an approach based on actual ground motion recordings. The results of the analyses show that significant differences in terms of exceedance probabilities of the design spectral ordinates occur between the two applied methodologies for larger magnitude earthquakes and small epicentral distances. Moreover, based on the results obtained, it appears that the minimum earthquake magnitudes causing exceedances of the design peak ground acceleration are quite far from the maximum magnitudes of the considered crustal seismic sources in the western part of Romania.