Re-assessment of peak ground accelerations for large magnitude Vrancea intermediate-depth earthquakes

Abstract

In this short paper, the peak ground acceleration estimates of four major Vrancea intermediate-depth earthquakes with moment magnitudes MW ≥ 6.9 which occurred in the twentieth century are re-assessed using a recently proposed procedure combining macroseismic intensity data with a ground motion model derived for this seismic source. An empirical relation between macroseismic intensity and peak ground acceleration is proposed in this study for Vrancea intermediate-depth earthquakes. The results show that the largest median updated peak ground accelerations are obtained in the case of the Vrancea MW 7.7 earthquake of November 1940. Moreover, for some cities, the updated peak ground accelerations are higher than the ones given in the current Romanian seismic design code. In addition, peak ground acceleration values in excess of 0.1 g are noticed for almost half of the Romanian territory in the case of the November 1940 and March 1977 Vrancea intermediate-depth seismic events.