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Following the ongoing debate about suitability of short-period sensor for seismic noise measurements at frequencies lower
than 1 Hz, in this study we compare recordings from two different seismometers (Güralp CMG-3ESPC and Mark L4C-3D) installed
side by side in the GeoForschungsZentrum laboratory. The comparison carried out in terms of Power Spectral Density and coherency
analysis shows an excellent agreement between the short-period and the broad-band recordings in the frequency band 0.2–20 Hz.
Therefore, this result highlights that with a calibrated short-period sensor one can obtain the same results that would be
obtained by using a broad-band seismometer in the band of engineering interest. 相似文献
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Sebastiano Foti Stefano Parolai Dario Albarello Matteo Picozzi 《Surveys in Geophysics》2011,32(6):777-825
Surface-wave dispersion analysis is widely used in geophysics to infer a shear wave velocity model of the subsoil for a wide
variety of applications. A shear-wave velocity model is obtained from the solution of an inverse problem based on the surface
wave dispersive propagation in vertically heterogeneous media. The analysis can be based either on active source measurements
or on seismic noise recordings. This paper discusses the most typical choices for collection and interpretation of experimental
data, providing a state of the art on the different steps involved in surface wave surveys. In particular, the different strategies
for processing experimental data and to solve the inverse problem are presented, along with their advantages and disadvantages.
Also, some issues related to the characteristics of passive surface wave data and their use in H/V spectral ratio technique
are discussed as additional information to be used independently or in conjunction with dispersion analysis. Finally, some
recommendations for the use of surface wave methods are presented, while also outlining future trends in the research of this
topic. 相似文献
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M. Mucciarelli M. Bianca R. Ditommaso M. R. Gallipoli A. Masi C. Milkereit S. Parolai M. Picozzi M. Vona 《Bulletin of Earthquake Engineering》2011,9(1):263-283
After the recent Central Italy Earthquake of the 6th April 2009 (Mw = 6.3), the Italian and German engineer and geophysicist
Task Force carried out a wide characterization of sites, buildings and damages. In Navelli, a town about 35 km far from epicentre,
heavy damage occurred on a reinforced concrete (RC) building that represent an anomalous case of damage, when compared with
those occurred in the neighbouring area. In this paper, characterization of the site and damage of the Navelli RC Building
is reported and discussed. We performed ambient noise and strong motion measurements, installing one three-directional accelerometer
on each floor of the structure and two in free-field, and we have carried out repeated measurements using a couple of three-directional
tromometers. In the mean time, a geological survey was carried out and the site response was investigated, with the aid of
down-hole measurements. It was thus possible to investigate the structural response and damage taking into account site condition.
One of the main results of this work is that repeating analyses using ambient noise measurements show that the main structural
frequencies reached after the first damaging shock are constant over time, and then the structural behaviour appears stationary
at long term. On the other hand, the strong motion recordings show that the building exhibits a transient non-stationary behaviour
as the fundamental frequency changes during each aftershock, then returning to the starting value after each event. 相似文献
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S. Ullah D. Bindi M. Pittore M. Pilz S. Orunbaev B. Moldobekov S. Parolai 《Bulletin of Earthquake Engineering》2013,11(2):385-399
Site response analysis plays an important role in seismic hazard and risk assessment, and in defining the optimal engineering design for civil structures. However, due to increasing urbanization, target areas are often too vast to be covered by standard approaches, resulting in large uncertainties in the spatial variability of the expected ground motion. Here, we propose a method to improve the spatial resolution of ground motion variability in terms of Standard Spectral Ratios (SSRs), using earthquakes recorded at a few selected sites for a relatively short amount of time, and seismic noise data collected over a denser grid, taking advantage of clustering and correlation analysis. The method is applied to Bishkek, Kyrgyzstan. Using the K-means clustering algorithm, three clusters of site response types have been identified, based on their similarity of SSRs. The cluster’s site responses were adopted for sites where only single station noise measurements were carried out, based on the results of correlation analysis. The spatial variability of the site response correlates well with the main geological features in the area. In particular, variability is noted from south to north, consistent with both the changes in the thickness of the sedimentary cover over the basin and in the Quaternary material outcropping at the surface. This method has therefore the potential to improve the estimation of site effects at the local scale in the future. 相似文献
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R. Ditommaso S. Parolai M. Mucciarelli S. Eggert M. Sobiesiak J. Zschau 《Bulletin of Earthquake Engineering》2010,8(3):705-722
The response of the soil-structure system near the Falkenhof Tower, Potsdam, Germany, has been monitored during the controlled
explosion of a bomb dating to World War II. We installed eight 3-component velocimetric stations within the building and three
in the surrounding area. We recorded several hours of seismic noise before and after the explosion, allowing the dynamic characterization
of the structure both with ambient noise and forced vibration. We then compared the frequencies values and modal shapes of
the structural modes evaluated both by analysing in the frequency domain the transfer functions and in the time-domain the
different signals. Moreover, we carried out an interferometric analysis of the recorded signals in order to study the structural
behaviour and to characterize the soil-structure interaction. Furthermore, we used normalized Short Time Fourier Transform
(STFT) for the continuous monitoring of the structural response, in order to highlight possible frequency variations of the
structural mode of vibration, and therefore of the structure’s behaviour. To assess structural frequencies and to compare
them with those evaluated by transfer functions, we used azimuth-dependent Fourier spectra. We also verified the suitability
of the Horizontal-to-Vertical Spectral Ratio (HVSR) for estimating the dynamic characteristics of buildings when only single
station seismic noise measurements are available. Regarding the structure-soil interaction, we identified the presence of
a wave field back-radiated from the structure within the low amplitude seismic noise signal. In fact, in the free-field seismic
noise recording spectra, peaks at frequencies consistent with those of the first two modes of the structure were recognized. 相似文献
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Monitoring the structural dynamic response of a masonry tower: comparing classical and time-frequency analyses 总被引:2,自引:2,他引:0
Rocco Ditommaso Marco Mucciarelli Stefano Parolai Matteo Picozzi 《Bulletin of Earthquake Engineering》2012,10(4):1221-1235
The monitoring of the evolution of structural dynamic response under transient loads must be carried out to understand the physical behaviour of building subjected to earthquake ground motion, as well as to calibrate numerical models simulating their dynamic behaviour. Fourier analysis is one of the most used tools for estimating the dynamic characteristics of a system. However, the intrinsic assumption of stationarity of the signal imposes severe limitations upon its application to transient earthquake signals or when the dynamic characteristics of systems change over time (e.g., when the frequency of vibration of a structure decreases due to damage). Some of these limitations could be overcome by using the Short Time Fourier Transform (STFT). However, the width of the moving window adopted for the analysis has to be fixed as a function of the minimum frequency of interest, using the best compromise between resolution in both the time and frequency domains. Several other techniques for time-frequency analysis of seismic signals recorded in buildings have been recently proposed. These techniques are more suitable than the STFT for the application described above, although they also present drawbacks that should be taken into account while interpreting the results. In this study, we characterize the dynamic behaviour of the Falkenhof Tower (Potsdam, Germany) while forced by ambient noise and vibrations produced by an explosion. We compare the results obtained by standard frequency domain analysis with those derived by different time-frequency methods. In particular, the results obtained by the standard Transfer Function method, Horizontal to Vertical Spectral Ratio (HVSR), Short Time Fourier Transform (STFT), Empirical Mode Decomposition (EMD) and S-Transform are discussed while most of the techniques provide similar results, the EMD analyses suffer some problems derived from the mode mixing in most of the Intrinsic Mode Functions (IMFs). 相似文献
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Microzonation of Potenza (Southern Italy) in terms of spectral intensity ratio using joint analysis of earthquakes and ambient noise 总被引:1,自引:1,他引:0
Angelo Strollo Stefano Parolai Dino Bindi Leonardo Chiauzzi Rossella Pagliuca Marco Mucciarelli Jochen Zschau 《Bulletin of Earthquake Engineering》2012,10(2):493-516
A temporary seismic network composed of 11 stations was installed in the city of Potenza (Southern Italy) to record local
and regional seismicity within the context of a national project funded by the Italian Department of Civil Protection (DPC).
Some stations were moved after a certain time in order to increase the number of measurement points, leading to a total of
14 sites within the city by the end of the experiment. Recordings from 26 local earthquakes (Ml 2.2−3.8 ) were analyzed to compute the site responses at the 14 sites by applying both reference and non-reference site techniques.
Furthermore, the Spectral Intensity (SI) for each local earthquake, as well as their ratios with respect to the values obtained
at a reference site, were also calculated. In addition, a field survey of 233 single station noise measurements within the
city was carried out to increase the information available at localities different from the 14 monitoring sites. By using
the results of the correlation analysis between the horizontal-to-vertical spectral ratios computed from noise recordings
(NHV) at the 14 selected sites and those derived by the single station noise measurements within the town as a proxy, the
spectral intensity correction factors for site amplification obtained from earthquake analysis were extended to the entire
city area. This procedure allowed us to provide a microzonation map of the urban area that can be directly used when calculating
risk scenarios for civil defence purposes. The amplification factors estimated following this approach show values increasing
along the main valley toward east where the detrital and alluvial complexes reach their maximum thickness. 相似文献
30.
In order to evaluate thefrequency dependence of site effects, thejoint analysis of the standard spectralratio technique with a sonogram approach isproposed (Joint Analysis of Sonogram andStandard Spectral Ratio). Two tools aresuggested: the enhanced sonograms andthe differential sonograms. Inparticular, the local geology effects areinvestigated by considering both theamplification of the seismic signals andtheir prolongation. Tests carried out onsynthetic signals show the capability ofthe sonogram approach to evaluate thefrequency-dependent lengthening of theseismic signal. The JASSSR is applied todata recorded by a dense local networkdeployed during the Umbria-Marche seismicsequence of 1997 and to data recorded inthe Volvi Test site (Euroseistest, Greece).The results show that using the JASSSR gives amore complete overview of the effects oflocal geology on seismic ground motion than maybe obtained by using the StandardSpectral Ratio alone. In particular, theeffect of secondary arrivals, both on theamplitude and on the lengthening of theseismic ground motion, can be pointed out.In addition, the characteristic frequencyof these arrivals can be evaluated. 相似文献