Seismic Hazard of Romania: Deterministic Approach

Rădulian, Mircea; Vaccari, Franco; Mândrescu, N.; Panza, G. F.; Moldoveanu, C. L.

doi:10.1007/978-3-0348-8415-0_13

Cited by 24 publications

(22 citation statements)

References 19 publications

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“…For the region under study, an a priori 3-D crustal model is available, which was assembled by Martin et al (2004a) and is based on results of previous studies in the Vrancea region including basement, Conrad and Moho maps and refraction profiles (Radulescu 1988;Raileanu et al 1994;Polonic 1996;Radulian et al 2000;Lenkey 1999;Hauser et al 2001Hauser et al , 2002. As a major improvement in comparison to previous crustal models of that region (which found application in earlier tomographic studies, e.g.…”

Section: A P R I O R I C Ru S Ta L M O D E Lmentioning

confidence: 99%

Improving depth resolution of teleseismic tomography by simultaneous inversion of teleseismic and globalP-wave traveltime data-application to the Vrancea region in Southeastern Europe

Weidle¹,

Widiyantoro²

2005

Geophysical Journal International

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SUMMARY Over the years, teleseismic tomography has developed to be a sophisticated method to study the Earth's upper mantle on a regional scale. Using data from tomographic experiments with temporary station networks, one faces some inherent problems, which include limited resolution at depth and artefacts due to a plane‐wave approximation at the bottom of the model volume. Simultaneous inversion of dense regionally recorded teleseismic and global P‐wave traveltime data provides an opportunity to overcome these specific problems. The calculation of the entire ray path using a 3‐D ray tracing algorithm and a non‐linear iterative inversion scheme allow to localize heterogeneities in the Earth's mantle and to improve resolution at depth. Application of a variable parametrization scheme provides not only a regional high‐resolution model but additionally allows to include a priori constrained structures such as a crustal model derived from independent studies. We investigated the effect of different inversion strategies for a priori constrained model parameters and found that, for upper‐mantle studies, one must allow further perturbation of the known velocity structure during inversion to avoid artefacts down to the mantle transition zone. We apply this approach to the Romanian Vrancea region in Southeastern Europe. The results show a near‐vertical, narrow high‐velocity body underneath that region extending down to 280 km depth, approximately outlining the narrowly spaced seismogenic volume and a deeper, differently oriented positive anomaly coupled to the shallower segment at the latter's southwestern edge. At north, northwest and west of the Vrancea region, we find an extended region of decreased seismic P‐wave velocity down to 200 km depth, being interpreted as a shallow lithosphere–asthenosphere boundary and asthenospheric mantle flow due to lateral migration of the high‐velocity body. From synthetic reconstruction tests, we found that inversion of the combined data set of regionally recorded teleseismic and global traveltime data enhances resolution up to depths greater than could be resolved by the teleseismic data alone.

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Section: A P R I O R I C Ru S Ta L M O D E Lmentioning

confidence: 99%

Improving depth resolution of teleseismic tomography by simultaneous inversion of teleseismic and globalP-wave traveltime data-application to the Vrancea region in Southeastern Europe

Weidle¹,

Widiyantoro²

2005

Geophysical Journal International

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“…For the Romanian events with M w > 6, the analysis of observed spectra indicates that, for a given magnitude, the corner frequencies of deep events are one order of magnitude higher than those of shallow earthquakes (RADULIAN et al, 1998). Using the same scaling, RADULIAN et al (2000a) successfully accomplished the deterministic hazard computations for Romania, corresponding to the Vrancea subcrustal earthquakes. Both sets of the original (GUSEV, 1983) and the modi®ed empirical source spectra scaling curves are presented in Figure 6.…”

Section: Vol 158 2001mentioning

confidence: 99%

Vrancea Source Influence on Local Seismic Response in Bucharest

Moldoveanu

Panza

2001

Pure appl. geophys.

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Ð 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 that allows easy parametric tests. Starting from the actually available strong motion database, we can make realistic predictions for the possible ground motion. The basic information necessary for the modeling consists of: (a) The representative mechanisms for the strong subcrustal events, (b) the average regional structural model, and (c) the local structure for Bucharest. Two scenario earthquakes are considered and the source in¯uence on the local response is analyzed in order to de®ne generally valid ground motion parameters, to be used in the seismic hazard estimations. The source has its own (detectable) contribution on the ground motion and its eects on the local response in Bucharest are quite stable on the transversal component (T), while the radial (R) and vertical (V) components are sensitive to the scenario earthquake. Although the strongest local eects aect the T component, both observed and synthetic, a complete determination of the seismic input for the built environment requires the knowledge of all three components of motion (R, V, T). The damage observed in Bucharest for the March 4, 1977 Vrancea event, the strongest earthquake to strike the city in modern times, is in agreement with the synthetic signals and local response. Figure 7Acceleration time series (R, V, and T components) at an array of 7 receivers equally spaced at 3 km, along the local pro®le of Bucharest setting considered in the simulations. The scenario earthquakes considered are the two dominant Vrancea strong events: (a) for V-1, and (b) for V-2. The signals for both sources are scaled for a M W 7.4 (M 0 1.26 á 10 +20 N m) using empirical source spectra curves (GUSEV, 1983) modi®ed for the deep intermediate-depth Vrancea shocks. Acceleration is given in cm/s 2 and time in seconds. Peak values correspond to MSK-64 macroseismic intensity 8.

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“…According to our limited knowledge, several studies on deterministic and probabilistic seismic hazard assessment for Romania, in terms of horizontal peak ground acceleration and/or macro-seismic intensities, were published by Lungu et al (1999Lungu et al ( , 2006, Musson (2000), Mäntyniemi et al (2003Mäntyniemi et al ( , 2004, Radulian et al (2000b), Ardeleanu et al (2005), Leydecker et al (2008), Mârza et al (1991), Sokolov et al (2009).…”

Section: Seismic Hazard Analysismentioning

confidence: 98%