GIULIANO F. PANZA 1,4, CARMEN CIOFLAN 2, M. KOUTEVA 3,4, I. PASKALEVA 3, F. ROMANELLI 4, GHEORGHE MARMUREANU 2
1 The Abdus Salam ICTP, SAND Group,
Strada Costiera 11, 34100 Trieste, Italy
2 NIEP, Calugareni St. 12, P.O.B. MG2,
76900 Bucharest-Magurele, Romania
3 CLSMEE-BAS, Acad. G. Bonchev 3, 1113
Sofia, Bulgaria
4 DST-University of Trieste, E. Weiss
4, 34127 Trieste, Italy
An advanced procedure for ground motion modelling, capable of synthesizing
the seismic ground motion from basic understanding of fault mechanism and
seismic wave propagation, is applied to the case studies of Bucharest (Romania)
and Russe, NE Bulgaria, exposed to the seismic hazard from Vrancea events.
Synthetic seismic signals along representative geological cross sections
in Bucharest and Russe have been computed and the energetic input spectra
have been derived both from the synthetic signals and the few existing records.
The theoretical signals are successfully compared with the available observations.
The site response has been calculated for three recent, strong and intermediate-depth,
Vrancea earthquakes: August 30, 1986 and May 30 and 31, 1990. The used approach
differs significantly from the today’s engineering design practice
that relays upon rock-site hazard maps and applies the site correction at
a later stage. The obtained results show that it is very useful to estimate
the site effect via waveform modelling, considering simultaneously the geotechnical
properties of the site, the position and geometry of the seismic source and
the mechanical properties of the propagation medium.
Key words: ground motion modelling, site response, intermediate-depth earthquakes, modal summation, finite differences, hybrid approach, modes coupling.