Re-assessment of peak ground accelerations for large magnitude Vrancea intermediate-depth earthquakes
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SHORT COMMUNICATION
Re-assessment of peak ground accelerations for large magnitude Vrancea intermediate-depth earthquakes Florin Pavel & Radu Vacareanu
Received: 12 August 2019 / Accepted: 31 August 2020 # Springer Nature B.V. 2020
Abstract In this short paper, the peak ground acceleration estimates of four major Vrancea intermediatedepth earthquakes with moment magnitudes MW ≥ 6.9 which occurred in the twentieth century are reassessed 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. Keywords Vrancea seismic source . Peak ground acceleration . Macroseismic intensity . Bayesian update
1 Introduction F. Pavel (*) : R. Vacareanu Technical University of Civil Engineering Bucharest, Bd. Lacul Tei, no. 122-124, Sector 2, 020396 Bucharest, Romania e-mail: [email protected]
The Vrancea intermediate-depth seismic source has produced five seismic events with moment magnitudes MW ≥ 6.4 in the period 1940–1990 (Table 1). Among these five earthquakes, the MW 7.7 seismic event of November 10, 1940, is the largest intermediate-depth earthquake occurring in Romania and in Europe in the twentieth century. Unfortunately, no ground motion recording was obtained from the 1940 seismic event. In the case of the 1977 event, three free-field recordings were obtained, only one of which is in Romania (the ground motion recorded at INCERC station in the eastern part of Bucharest). For the other three seismic events from 1986 and 1990 (two events in May), the number of available ground motion recordings is between 36 and 52 (Pavel et al. 2014). Relevant information regarding the damage and casualties produced by the two largest Vrancea intermediate-depth earthquakes of 1940 and 1977 can be found in the papers of Georgescu and Pomonis (2012) or Georgescu and Pomonis (2018). Unfortunately, the information regarding the next two Vrancea intermediate-depth seismic events of 1986 and 1990 is rather scarce, the field trip report of EEFIT (Pomonis et al. 1990) being a valuable source of information regarding the 1990 Vrancea events. In this paper, we aim at improving the knowledge regarding the peak ground acceleration estimates in various sites in Romania using the combination between macroseismic intensity data (Kronrod et al. 2013) and the ground motion model of Vacareanu et al. (2015a) which was specifically deriv
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