Physical Properties Of The Upper Sedimentary Rocks In Bucharest Metropolitan Area

Bălă, Andrei; Rãileanu, V.; Zihan, Ion; Grecu, Bogdan; Ciugudean, Viorica

doi:10.3997/2214-4609-pdb.26.p13-04

Cited by 5 publications

(11 citation statements)

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“…Inferred near surface shear wave velocity turns out to be close to the mean value of the boxes as is consistent with the displayed trade‐off. The values are also consistent with average velocities obtained from shallow shear wave velocity profiles that are obtained in boreholes (Bala et al 2006).…”

Section: Inversion For Subsurface Structuresupporting

confidence: 89%

“…First at local scale (upper ≈100 m), several near‐surface studies were used to determine mean velocities and densities of seven characteristic Quaternary layers as well as their rough geometry underneath Bucharest city (Mândrescu et al 2004, 2007). Detailed measurements at a few sites reveal a complex layering with highly varying seismic velocities in the uppermost Quaternary sediments (Bala et al 2005). At crustal scale, a NNE–SSW long‐range seismic refraction line (VRANCEA99) was measured through Bucharest (Hauser et al 2001; Raileanu et al 2005).…”

Section: Introductionmentioning

confidence: 99%

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The shear wave velocity underneath Bucharest city, Romania, from the analysis of Love waves

Sèbe

Forbriger

Ritter

2009

Geophysical Journal International

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S U M M A R YFrom the dispersion of Love waves, we infer models of shear wave velocity structure underneath Bucharest (Romania) at depths down to 2 km that can contribute to seismic hazard estimation. Waves from eight regional events recorded during 10 months with a network of 34 seismic broad-band stations of the URban Seismology (URS) experiment are used. Although these events provide poor azimuthal coverage the data reliably constrain a shear wave velocity model with an interface between the Neogene and the Cretaceous sediments that is dipping northwards towards the Carpathian mountains. Array processing techniques that account for non-uniform wave propagation are used to estimate the dispersion of structural phase velocity. From this, we infer subsurface structure at three different latitudes. The Neogene sediments are represented by a gradient layer with no significant lateral variation. Shear wave velocity increases from approximately 400 m s −1 near the surface to 1 km s −1 at 1 km depth and 5 km in the south, and to 1.35 km s −1 at 1.5 km depth and 5 km in the north from the centre of Bucharest, respectively. For the half-space representing the Cretaceous sediments, we obtain shear wave velocities of 2.7-2.9 km s −1 . The results are consistent with results from boreholes and shallow seismics for the near-surface structure and results from receiver function studies and crustal refraction seismic studies for the deeper structure. The details of the Neogene layer comprising a vertical gradient fill a gap in existing models of the subsurface structure of Bucharest and can contribute to modelling of seismic hazard for the city. Since the signalto-noise ratio restricted useful data to the frequency range from 90 to 290 mHz, the inversion could not constrain the near-surface velocity independently. Due to strong trade-off between near-surface velocity and depth of half-space, the latter had to be introduced as a priori data from previous studies.

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Section: Inversion For Subsurface Structuresupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

The shear wave velocity underneath Bucharest city, Romania, from the analysis of Love waves

Sèbe

Forbriger

Ritter

2009

Geophysical Journal International

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“…For the entire Lisan section, we set a shear modulus equal to 100 MPa, which is in agreement with other experiments of soft sediments (e.g. Gannon et al 1999;Schneider et al 1999;Chetrit 2004;Yuan-qiang & Xu 2004;Bala et al 2006). The rock density for the whole Lisan section was set to 1400 kg m −3 , and the maximum tensile strength is about T o = 0.1 MPa (Arkin & Michaeli 1986).…”

Section: Ro C K a N D F L U I D P Ro P E Rt I E Ssupporting

confidence: 60%

“…Therefore, we used 0.4 for the Poisson's ratio, which is also in agreement with the suggested 0.3-0.5 values of clay-rich sediments (e.g. Gee-Clough et al 1994;Vallejo & Lobo-Guerrero 2002;Chetrit 2004;Othman 2005;Bala et al 2006). For the dykelets developed close to the surface, we used a range of shear modulii between 50 to 100 MPa (e.g.…”

Section: Ro C K a N D F L U I D P Ro P E Rt I E Smentioning

confidence: 83%

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Velocities and driving pressures of clay-rich sediments injected into clastic dykes during earthquakes

Levi¹,

Weinberger²,

Eyal³

et al. 2008

Geophysical Journal International

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S U M M A R YWe studied the velocities and driving pressures associated with clastic-dyke formation in the Ami'az plain, where hundreds of clastic dykes cross-cut the soft rock of the late Pleistocene lacustrine Lisan Formation, within the seismically active Dead Sea basin. Flow of clastic material into fractures and opening of the fractures are two mechanisms that occur during earthquake-induced clastic dyke emplacement. Two analytic models were established, based on field observations and experimental viscosity tests, to estimate the velocities and driving pressures that were associated with dyke emplacement: (a) a channel flow for upward injection of a clay-water mixture and (b) a profile of fracture dilation based on the elastic theory analysis. The two models predict that pressures between 1 and 10 MPa are generated in the source layer and dykes in the last stage of the injection process. In addition, the channel flow model predicts that the injection velocity reaches metres to tens of metres per second and the emplacement time of the clastic dykes is on a scale of seconds. It is suggested that the high pressure values represent the static stress drop during earthquake events or represent dynamic stresses resulting from the seismic waves which passed through the soft lacustrine rocks. In both cases, the predicted high pressure values indicate that the clastic dyke was emplaced in close proximity of an active segment of the Dead Sea Fault during the late Pleistocene-Holocene.

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Variability of Ground Motion Amplitudes Recorded in Bucharest Area during Vrancea Intermediate‐Depth Earthquakes

Pavel

2021

Shock and Vibration

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This study focuses on the assessment of the correlation and variability of ground motion amplitudes recorded in Bucharest area during Vrancea intermediate-depth earthquakes from a database of 119 pairs of horizontal components. Empirical models for the evaluation of the peak ground velocity and displacement from spectral accelerations are proposed in this study. The distribution of the shear wave velocities from 41 boreholes at specific depths appears to follow a normal probability distribution. The analysis performed in this study has also shown that the variability of peak ground velocities and displacements does not appear to be influenced by the earthquake magnitude. In addition, it was observed that the variability in terms of shear wave velocities at specific depths is smaller than the variability of the spectral amplitudes of the recorded ground motions. The empirical site-amplification factors from the Eurocode 8 draft fail to capture the long-period spectral amplifications observed in Bucharest area during large magnitude Vrancea intermediate-depth earthquakes.

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Physical Properties Of The Upper Sedimentary Rocks In Bucharest Metropolitan Area

Cited by 5 publications

References 0 publications

The shear wave velocity underneath Bucharest city, Romania, from the analysis of Love waves

The shear wave velocity underneath Bucharest city, Romania, from the analysis of Love waves

Velocities and driving pressures of clay-rich sediments injected into clastic dykes during earthquakes

Variability of Ground Motion Amplitudes Recorded in Bucharest Area during Vrancea Intermediate‐Depth Earthquakes

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