Modelling, for Microzonation Purposes, of the Seismic Ground Motion in Bucharest, Due to the Vrancea Earthquake of May 30, 1990

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The mapping of the seismic ground motion in Bucharest, due to the strong Vrancea earthquakes is carried out using a complex hybrid waveform modeling method which combines the modal summation technique, valid for laterally homogeneous anelastic media, with finite-differences technique, and optimizes the advantages of both methods. For recent earthquakes, it is possible to validate the modeling by comparing the synthetic seismograms with the records. We consider for our computations the frequency range from 0.05 to 1.0 Hz and control the synthetic signals against the accelerograms of the Magurele station, low-pass filtered with a cut-off frequency of 1.0 Hz of the 3 last major strong (Mw > 6) Vrancea earthquakes. Using the hybrid method with a double-couple seismic source approximation, scaled for the source dimensions and relatively simple regional (bedrock) and local structure models, we succeeded in reproducing the recorded ground motion in Bucharest at a satisfactory level for seismic engineering. Extending the modeling to the entire territory of the Bucharest area, we construct a new seismic microzonation map, where five different zones are identified by their characteristic response spectra

Section: Discussionmentioning

confidence: 99%

Deterministic Approach for the Seismic Microzonation of Bucharest

Cioflan

Apostol

Moldoveanu

et al. 2004

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“…The first studies devoted to the mapping of the seismic ground motion in Bucharest due to the strong Vrancea earthquakes by means of synthetic signals have been carried out by MOLDOVEANU and PANZA (1999) and MOLDOVEANU et al (2000. The numerical method implied is a complex hybrid waveform modeling (FA¨H et al, 1994;PANZA et al, 2001) that combines modal summation (PANZA, 1985;VACCARI et al, 1989;FLORSCH et al, 1991;ROMANELLI et al, 1996) with finitedifference techniques (ALTERMAN and KARAL, 1968;BOORE, 1972;KELLY et al, 1976), and allows us easy parametric tests.…”

Section: Ground Motion Modelingmentioning

confidence: 99%

“…The input information necessary for the modeling consists of the source mechanism, the average regional structural model, and the laterally heterogeneous anelastic local structure. MOLDOVEANU andPANZA (1999) andMOLDOVEANU et al (2000) succeeded in modeling the ground motion in Bucharest for the May 30, 1990, Vrancea event with good accuracy for microzonation purposes. The frequency window considered in the computations extends up to 1 Hz and allows us the modeling of the seismic input appropriate for 10-storey and higher buildings.…”

Section: Ground Motion Modelingmentioning

confidence: 99%

Microzonation of Bucharest: State-of-the-Art

Moldoveanu

Rădulian

Marmureanu

et al. 2004

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The 1940 (Mw 1⁄4 7.7) and 1977 (Mw 1⁄4 7.4) Vrancea earthquakes (Romania) inflicted heavy damage and casualties in Bucharest and the statistics indicate a recurrence interval of 25 years for Mw ‡ 7.0 events. Under these circumstances, the seismic microzonation represents important information for detailed urban planning that establishes an appropriate level of preparedness to the earthquake threat. This paper reviews the main studies concerning the seismicity of the Vrancea region, the site conditions of the city, the characterization of the building stock, and the codes of practice that regulate the antiseismic design. The first-order microzonation of Bucharest was performed starting from the existing database of structural and geotechnical parameters. New insights originating from direct instrumental observation and interpretation of the local effects as well as realistic numerical modeling that update and improve the input data necessary for a detailed microzoning map of the city are also discussed

“…FA¨H et al (1993a, b) developed a hybrid method that combines the modal summation technique (PANZA, 1985;PANZA and SUHADOLC, 1987;FLORSCH et al, 1991;PANZA et al, 2001) with finite differences (VIRIEUX, 1984(VIRIEUX, , 1986LEVANDER, 1988), exploiting both methods to their best. In the framework of the UNESCO-IUGS-IGCP Project 414 ''Realistic Modelling of Seismic Input for Megacities and Large Urban Areas'' (PANZA et al, 1999a), this hybrid approach has been successfully applied for the purpose of the deterministic seismic microzoning in several urban areas: Beijing (SUN et al, 1998), Benevento (FA¨H andSUHADOLC, 1995;SUHADOLC, 1998), Bucharest (MOLDOVEANU andPANZA, 1999;MOLDOVEANU et al, 2000), Catania (ROMANELLI et al, 1998a, b), Mexico City (FA¨H et al, 1994, Rome (FA¨H et al, 1993b;, Naples (NUNZIATA et al, 1995(NUNZIATA et al, , 2000, Santiago de Cuba (ALVAREZ et al, 2001) and Delhi (PARVEZ et al, 2002).…”

Section: Site-specific Strong Ground Motion Modellingmentioning

confidence: 99%

Site-specific Microzonation Study in Delhi Metropolitan City by 2-D Modelling of SH and P-SV Waves

Panza

Parvez

Vaccari

2004

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Delhi – the capital of India lies on a severe earthquake hazard threat not only from local earthquakes but also from Himalayan events just 200–250 km apart. The seismic ground motion in a part of Delhi City is computed with a hybrid technique based on the modal summation and the finite-difference scheme for site-specific strong ground motion modelling. Complete realistic SH and P-SV wave seismograms are computed along two geological cross sections, (1) north-south, from Inter State Bus Terminal (ISBT) to Sewanagar and (2) east-west, from Tilak Bridge to Punjabi Bagh. Two real earthquake sources of July 15, 1720 (MMI 1⁄4 IX, M 1⁄4 7:4) and August 27, 1960 (M 1⁄4 6:0) have been used in modelling. The response spectra ratio (RSR), i.e. the response spectra computed from the signals synthesized along the laterally varying section and normalized by the response spectra computed from the corresponding signals, synthesized for the bedrock reference regional model, have been determined. As expected, the sedimentary cover causes an increase of the signal amplitude, particularly in the radial and transverse components. To further check the site-effects, we reversed the source location to the other side of the cross section and recomputed the site amplifications. There are only a few sites where a large amplification is invariant with respect to the two source locations considered. The RSR ranges between 5 to 10 in the frequency range from 2.8 to 3.7 Hz for the radial and transverse components of motion along the NS cross section. Along the EW cross section RSR varies between 3.5 to 7.5 in the frequency range from 3.5 to 4.1 Hz. The amplification of the vertical component is considerable at high frequency (>4 Hz.) whereas it is negligible in lower frequency range