Assessment of the ground motion levels for the Vrancea (Romania) November 1940 earthquake

Abstract

This short paper focuses on the evaluation of the ground motions levels likely experienced in ten cities seriously damaged during the November 1940 intermediate-depth Vrancea (Romania) earthquake (MW = 7.7). In the first step of the analysis, the ground motion levels are evaluated using a recently developed ground motion model (Vacareanu et al. in J Earthq Eng 19(3):535–562, 2015) for the Vrancea intermediate-depth seismic source. Next, the stochastic method of simulation (Boore in Pure App Geophys 160:635–676, 2003) is employed in the same purpose. In order to include the nonlinear soil effects into the results of the stochastic simulations, a dedicated amplification function is derived from the ground motions recorded during two large magnitude Vrancea earthquakes in 1986 and 1990. The results obtained for the November 1940 Vrancea earthquake show that the largest spectral ordinates are obtained when the nonlinear soil effects are taken into consideration, while the peak ground accelerations are in almost all cases in excess of 0.15 g. In addition, the results for Bucharest are validated through a site-specific response analysis performed using a soil profile from the literature. This site response analysis for the 1940 seismic event reveals long-period spectral amplitudes, similar to the ones observed in Bucharest during the Vrancea 1977 earthquake.