排序方式: 共有52条查询结果,搜索用时 812 毫秒
41.
Bojana Petrovic Stefano Parolai Giovanna Pianese S. Umit Dikmen Bolot Moldobekov Sagynbek Orunbaev Roberto Paolucci 《Bulletin of Earthquake Engineering》2018,16(2):613-641
In this study, the joint deconvolution is applied to recordings of three test cases located in the cities of Bishkek, Kyrgyzstan, Istanbul, Turkey, and Mexico City, Mexico. Each test case consists of a building equipped with sensors and a nearby borehole installation in order to investigate different cases of coupling (impedance contrasts) between the building and the soil by analyzing the wave propagation through the building-soil-layers, and hence resolving the soil–structure-interactions. The three installations considering different dynamic characteristics of buildings and soil, and thus, different building-soil couplings, are investigated. The seismic input (i.e., the part of the wave field containing only the up-going waves after removing all down-going waves) and the part of the wave field that is associated with the waves radiated back from the building are separated by using the constrained deconvolution. The energy being radiated back from the building to the soil has been estimated for the three test cases. The values obtained show that even at great depths (and therefore distances), the amount of wave field radiated back by the building to the soil is significant (e.g., for the Bishkek case, at 145 m depth, 10% of the estimated real input energy is expected to be emitted back from the building; for Istanbul at 50 m depth, the value is also 10–15% of the estimated real input energy while for Mexico City at 45 m depth, it is 25–65% of the estimated real input energy). Such results confirm the active role of buildings in shaping the wave field. 相似文献
42.
One of the most important tasks in seismology and applied geophysics is the identification of the different kinds of waves that form a seismic record by means of polarization analysis. In particular, this involves the extraction of body waves (linear polarization) or surface waves (mostly elliptical polarization) from a set of seismic data and which forms a key point in several studies. 相似文献
43.
We derive S-wave attenuation characteristics, earthquake source parameters and site amplification functions at seismic stations
used for earthquake early warning in the Irpinia–Basilicata region, using non-parametric spectral inversion of seismograms
from 49 local events with M
L = 1.5–3.1. We obtain relatively low Q values (Q
0 = 28 at a frequency of 1 Hz) in conjunction with a strong frequency-dependence (close to linear). The source spectra can
be satisfactorily modeled using the omega-square model, with stress drops ranging between 0.01–2 MPa, and in the narrow magnitude
range available for analysis, the source spectra seem to scale self-similarly. The local magnitude M
L shows a linear correlation with moment magnitude M
W, however with a systematic underestimation by about 0.5-magnitude units. The results obtained in this work provide important
insights into the ground-motion characteristics that are required for appropriate seismic hazard assessment and are of practical
relevance for a suite of applications, such as the calibration of ground-motion prediction equations or the correction for
site amplification in earthquake early warning and rapid calculation of shake-maps for seismic emergency management. 相似文献
44.
S. Foti S. Parolai P. Bergamo G. Di Giulio M. Maraschini G. Milana M. Picozzi R. Puglia 《Bulletin of Earthquake Engineering》2011,9(6):1797-1820
This paper reports on site characterization for a set of accelerometric stations of the RAN (Italian accelerometric network)
with specific attention to the shear wave velocity profile. The latter is indeed of primary importance for the usability of
the accelerometric database. Surface wave analysis has been chosen as the primary investigation method since it offers the
possibility of reaching the required accuracy with reasonable costs. A range of different techniques, both of the active-source
and passive-source types, has been adopted to cope with the objectives of the characterization in relation to specific geological
settings. Quality assessment of experimental data has been implemented to check the consistency of the measurements also with
respect to the fundamental hypotheses of the method. Strategies to improve the reliability and robustness of the surface wave
data inversion were exploited in order to mitigate problems arising from solution non-uniqueness and influence of higher modes
in the propagation. Comparisons with independent borehole tests, available at some specific sites, confirm the reliability
of the results. Although the research program covered only a subset of the network, the obtained results show the importance
of specific experimental investigations aimed at estimating the shear wave velocity profile. Indeed the results lead to a
re-classification of several sites with respect to the preliminary classification based on surface geology. Within this context,
four selected case histories are reported in the present paper. 相似文献
45.
D. Bindi L. Luzi S. Parolai D. Di Giacomo G. Monachesi 《Bulletin of Earthquake Engineering》2011,9(6):1941-1959
In this work, we investigate the site amplification effects observed in the Norcia plain, Central Italy. Data from 30 selected
local earthquakes (2 ≤ Ml ≤ 4.1) recorded by a temporary seismic network composed by 15 stations, are analyzed to determine
the spatial variability of site effects. Both the Horizontal-to-Vertical spectral ratio and the Standard Spectral Ratio techniques
are applied to estimate the site amplification effects. The results show that most of the sites in the valley are affected
by strong amplifications (up to a factor of 20) in the frequency range 0.5–5 Hz. The value of the fundamental frequency of
resonance is strictly dependent on the location within the basin and on the sediment thickness. Strong amplifications also
affect the vertical components. The time-frequency analysis performed on a station located inside the basin shows the presence
of a large spectral amplitudes after the S-wave phase, not observed on a station located on the bedrock, suggesting the presence
of locally generated wave trains. Then, in agreement with earlier observations for other alluvial basins in Central Italy,
2D–3D effects play an important role in determining the site amplification effects in Norcia. 相似文献
46.
D. Bindi M. Mayfield S. Parolai S. Tyagunov U.T. Begaliev K. Abdrakhmatov B. Moldobekov J. Zschau 《Soil Dynamics and Earthquake Engineering》2011
A risk scenario for Bishkek, capital of the Kyrgyz Republic, is evaluated by considering a magnitude 7.5 earthquake occurring over the Issyk-Ata fault. The intensity values predicted through the application of an attenuation relationship and a recently compiled vulnerability composition model are used as inputs for seismic risk assessment, carried out using the Cedim Risk Estimation Tool (CREST) code. Although the results of this study show a reduction by as much as a factor of two with respect to the results of earlier studies, the risk scenario evaluated in this paper confirms the large number of expected injuries and fatalities in Bishkek, as well as the severe level of building damage. 相似文献
47.
S. Parolai D. Bindi S. Ullah S. Orunbaev S. Usupaev B. Moldobekov H. Echtler 《Journal of Seismology》2013,17(2):707-719
We present results from a vertical array of accelerometers that was recently installed in Bishkek (Kyrgyzstan) with the long-term aim of recording strong motion data. Taking advantage of recordings of a Mb 4.7 earthquake that occurred 40 km from the array site during the installation phase, we provide results of some preliminary data analysis. First, estimates of the S-wave velocity and Qs structure are deduced by the inversion of the deconvolved wavefield between the sensors in the borehole. Furthermore, the application of the nonstationary ray decomposition Kinoshita (Earth Planets Space 61:1297-1312, 2009) allowed at least three reflectors in the shallow velocity structure below the array to be identified. The complex nature of the wavefield (with up-going, down-going waves, and converted phases) due to the coarse, unconsolidated subsoil structure is highlighted by means of numerical simulations of ground motion. 相似文献
48.
Topographic versus stratigraphic amplification: mismatch between code provisions and observations during the L’Aquila (Italy, 2009) sequence 总被引:1,自引:0,他引:1
M. R. Gallipoli M. Bianca M. Mucciarelli S. Parolai M. Picozzi 《Bulletin of Earthquake Engineering》2013,11(5):1325-1336
During the L’Aquila seismic sequence (Italy, 2009) we had the opportunity to install temporary accelerometric stations to study the role of seismic site amplification in damage enhancement. Two of the monitored sites, Castelnuovo and Navelli were also a good test for the recently introduced Italian seismic code (NTC08 2008) that prescribes an aggravation factor for slopes and ridges. Castelnuovo was an ideal situation to check the rule proposed for the distribution of amplification as a function of the position along a slope, while Navelli provided the possibility to test the almost equivalent factors that NTC08 sets for stratigraphic and topographic amplification (respectively up to 40 and 60 %). In neither case the observation matches code provisions. For Castelnuovo, there is a frequency dependence that shows as the code is over-conservative for short periods but fails to predict amplification in the intermediate range. For Navelli, the code provision is verified for long periods, but in the range around the site resonance frequency the stratigraphic amplification proves to be three times more important than the topographic one. 相似文献
49.
—?Thirty-three earthquakes which occurred in the Central Apennines (Italy) with Ml ranging from 2.4 to 3.7 have been spectrally analysed using digital recordings from twelve stations of the Rete Sismometrica Marchigiana (RSM) network. Data corrected for geometrical spreading and quality factor Q have been inverted by means of the Generalised Inversion Technique. Site responses have been compared with those obtained by H/V ratio. Site amplifications have been observed both at stations placed on Pleistocene sediments and at one station located at 1800?m altitude. Source parameters have been calculated by fitting the spectra with an automatic procedure adopting the ω2 source model. The seismic moments range from 9.23?×?1019 to 4.28?×?1021 dyne-cm with an average M 0 (S) to M 0 (P) ratio of 1.13?±?0.38. The stress drops are generally low and they vary between 1.1 and 10.2?bar when estimated by using S source spectra, and between 0.5 and 7.1?bar when the P-source spectra are fitted. For the considered range of seismic moments we observe that the stress drop does not have significant dependence on event size. 相似文献
50.
A. Strollo S. M. Richwalski S. Parolai M. R. Gallipoli M. Mucciarelli R. Caputo 《Bulletin of Earthquake Engineering》2007,5(3):347-362
On 31 October and 1 November 2002, the Basso Molise area (Southern Italy) was struck by two earthquakes of moderate magnitude
(M
L = 5.4 and 5.3). The epicentral area showed a high level of damage, attributable both to the high vulnerability of existing
buildings and to site effects caused by the geological and geomorphological settings. Specifically, the intensity inside the
town of San Giuliano di Puglia was two degrees higher than in neighbouring towns. Also, within San Giuliano di Puglia, the
damage varied notably. The site response in the city was initially evaluated from horizontal-to-vertical spectral ratios (HVSR)
from a limited number of strong motion recordings of the most severe aftershocks. Several microtremor measurements were also
available. Both data sets indicated the simultaneous presence of two amplification peaks: one around 6 Hz, attributed in previous
studies to the strong, shallow impedance contrast among landfill/clay and calcarenites, and one at 2 Hz related to the first
S-wave arrivals and predominantly seen only on one receiver component. Further studies performed on weak-motion recordings
also showed strong amplification on the vertical receiver component, thus indicating an underestimation of the amplification
by the HVSR technique. Additionally, a 2D-model of the geology of the sub-surface was developed, reproducing the flower-shaped
structure generated during the late orogenic transpressive regime. The numerical (finite-difference hybrid) simulation reproduced
the two peaks of the observed data at slightly higher frequencies. The model also confirmed that the borders of the flower
structure define a boundary between amplification levels, with higher amplification inside. 相似文献