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1.
A detailed numerical simulation of the ground motion and a site response analysis for two towns in the Marche Region (Treia
and Cagli) is carried out on the basis of structural models deduced from available geological and geophysical data. In both
cases, the reference event is an M = 5.7 earthquake associated with a normal fault located beneath each town. The ground motion is computed using the 2D spectral
element method (SPEM 2D). The method solves the propagation of the seismic field through complex geological structures and
enables an estimate of the effects of deep crustal structure, superficial geology, and topography on ground motion. Numerical
simulations of the seismic field are performed along 2D vertical planes containing the seismic source. Strong ground motion
has not been yet recorded in the two towns; therefore, the numerical simulation of ground motion represents a way to overcome
the lack of instrumental data. The simulations carried out for Treia show that ground motion is influenced by both source
mechanism and effects due to propagation through the geological structure, while ground motion in Cagli features strong local
effects, caused by the presence of alluvial deposits under a large area of the town. 相似文献
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R. Maresca L. Nardone G. Pasquale F. Pinto F. Bianco 《Pure and Applied Geophysics》2012,169(7):1173-1188
The effects of surface geology on ground motion provide an important tool in seismic hazard studies. It is well known that the presence of soft sediments can cause amplification of the ground motion at the surface, particularly when there is a sharp impedance contrast at shallow depth. The town of Avellino is located in an area characterised by high seismicity in Italy, about 30?km from the epicentre of the 23 November 1980, Irpinia earthquake (M?=?6.9). No earthquake recordings are available in the area. The local geology is characterised by strong heterogeneity, with impedance contrasts at depth. We present the results from seismic noise measurements carried out in the urban area of Avellino to evaluate the effects of local geology on the seismic ground motion. We computed the horizontal-to-vertical (H/V) noise spectral ratios at 16 selected sites in this urban area for which drilling data are available within the first 40?m of depth. A Rayleigh wave inversion technique using the peak frequencies of the noise H/V spectral ratios is then presented for estimating Vs models, assuming that the thicknesses of the shallow soil layers are known. The results show a good correspondence between experimental and theoretical peak frequencies, which are interpreted in terms of sediment resonance. For one site, which is characterised by a broad peak in the horizontal-to-vertical spectral-ratio curve, simple one-dimensional modelling is not representative of the resonance effects. Consistent variations in peak amplitudes are seen among the sites. A site classification based on shear-wave velocity characteristics, in terms of Vs30, cannot explain these data. The differences observed are better correlated to the impedance contrast between the sediments and basement. A more detailed investigation of the physical parameters of the subsoil structure, together with earthquake data, are desirable for future research, to confirm these data in terms of site response. 相似文献
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Seismic wave amplification: Basin geometry vs soil layering 总被引：1，自引：0，他引：1
J.F. Semblat M. Kham E. Parara P.Y. Bard K. Pitilakis K. Makra D. Raptakis 《Soil Dynamics and Earthquake Engineering》2005,25(7-10):529-538
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Local site effect microzonation of Lorca town (SE Spain) 总被引：1，自引：0，他引：1
M. Navarro A. García-Jerez F. J. Alcalá F. Vidal T. Enomoto 《Bulletin of Earthquake Engineering》2014,12(5):1933-1959
Local site effect assessment based on subsurface ground conditions is often the key to evaluate urban seismic hazard. The site effect evaluation in Lorca town (south-eastern Spain) started with a classification of urban geology through the geological mapping at scale 1:10,000 and the use of geotechnical data and geophysical surveys. The 17 geological formations identified were classified into 5 geological/seismic formations according to their seismic amplification capacity obtained from ambient vibration measurements as well as from simultaneous strong motion records. The shear-wave velocity structure of each geological/seismic formation was evaluated by means of inversion of Rayleigh wave dispersion data obtained from vertical-component array records of ambient noise. Nakamura’s method was applied to determine a predominant period distribution map. The spectral amplification factors were fourfold the values recorded in a reference hard-rock site. Finally, the capability of this study for explaining the damage distribution caused by the May 11th, 2011 Lorca destructive earthquake (Mw \(=\) 5.2) was examined. The methods used in this work are of assistance to evaluate ground amplification phenomena in urban areas of complex geology as Lorca town due to future earthquakes with applicability on urban seismic risk management. 相似文献
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This paper presents an integrated approach for evaluating seismic hazard and establishing ground motion at a site. In this approach, we combine the advantage of probabilistic and deterministic seismic hazard analyses and generate synthetic ground motion by considering the characteristics of seismic source, path attenuation, and local soil condition. Furthermore, uncertainties in seismic and soil parameters are taken into account. The proposed approach can be used to establish site-specific ground motion for engineering applications. 相似文献
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This is the 6th contribution in the series of Historical Notes on seminal concepts in earthquake engineering and structural dynamics. It documents the origins and early developments (from the 1880s through 1992) of the effects of site geology on seismic ground motion. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Observations from many recent strong motion events have shown the importance of local soil conditions and non-linear soil behaviour on the seismic ground response (site effects). As demonstrated by previous seismic microzoning studies (Lebrun et al.) [1]), as well as by at least three historical major earthquakes, Pointe-à-Pitre is prone to strong site effects, due to the particular geology of the area. In this paper, we present a comparison between the strong-motion data available from the stations operating on the swampy site of Pointe-à-Pitre airport and the ground motions derived from 1D non-linear finite element simulations.Results show that, for moderate to strong ground motions, 1D simulations reproduce the main characteristics of site response in terms of duration, energy distribution, amplitude and frequency content. It also shows the importance of very superficial soft layers as peat or saturated mud in low frequency site effects simulations. This point is important for further engineering studies since such very soft formations overlain by stiffer landfills are commonly expected in the Antilles context. Our work also shows that Anderson's criteria, used to quantify the goodness-of-fit of simulated ground motions to the observed ones, appear to be an interesting diagnostic tool for testing the quality of numerical simulations from an engineering point of view. 相似文献
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It is commonly understood that earthquake ground excitations at multiple supports of large dimensional structures are not the same. These ground motion spatial variations may significantly influence the structural responses. Similarly, the interaction between the foundation and the surrounding soil during earthquake shaking also affects the dynamic response of the structure. Most previous studies on ground motion spatial variation effects on structural responses neglected soil–structure interaction (SSI) effect. This paper studies the combined effects of ground motion spatial variation, local site amplification and SSI on bridge responses, and estimates the required separation distances that modular expansion joints must provide to avoid seismic pounding. It is an extension of a previous study (Earthquake Engng Struct. Dyn. 2010; 39 (3):303–323), in which combined ground motion spatial variation and local site amplification effects on bridge responses were investigated. The present paper focuses on the simultaneous effect of SSI and ground motion spatial variation on structural responses. The soil surrounding the pile foundation is modelled by frequency‐dependent springs and dashpots in the horizontal and rotational directions. The peak structural responses are estimated by using the standard random vibration method. The minimum total gap between two adjacent bridge decks or between bridge deck and adjacent abutment to prevent seismic pounding is estimated. Numerical results show that SSI significantly affects the structural responses, and cannot be neglected. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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C. O. Cioflan B. F. Apostol C. L. Moldoveanu G. F. Panza GH. Marmureanu 《Pure and Applied Geophysics》2004,161(5-6):1149-1164
— 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. 相似文献
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Seismic site amplification studies are generally used to assess the effects of local geology and soil conditions on ground motion characteristics. Although extensive reviews on site amplification phenomena associated with stratigraphic effects can be found in the specialized literature, it should be pointed out that most of the practical applications have been limited to the study of vertically propagating shear horizontal (SH) waves, i.e., to the 1-D soil amplification problem. Furthermore, little attention, if any, has been devoted to the study of the effects of non-vertically incident SH waves on surface accelerograms and on the earthquake response of structures. In the present work, the study is extended to an investigation of 2-D site amplification of non-vertically propagating seismic shear waves in multilayered viscoelastic soil deposits. Sensitivity analyses of the effects of non-vertical incidence on site amplification functions are performed based on site geotechnical data collected from post-seismic investigations of the 1980 El-Asnam earthquake. Analytical results are discussed in terms of seismic site transfer functions, spectral ratios, surface acceleration time histories, and structural response spectra for different values of wave incidence angle. Both bedrock and rock outcropping cases are examined. 相似文献
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Flavio Poletto Lorenzo Petronio Biancamaria Farina Andrea Schleifer 《Geophysical Prospecting》2011,59(3):464-476
We present the results of a seismic interferometry experiment in a shallow cased borehole. The experiment is an initial study for subsequent borehole seismic surveys in an instrumented well site, where we plan to test other surface/borehole seismic techniques. The purpose of this application is to improve the knowledge of the reflectivity sequence and to verify the potential of the seismic interferometry approach to retrieve high‐frequency signals in the single well geometry, overcoming the loss and attenuation effects introduced by the overburden. We used a walkaway vertical seismic profile (VSP) geometry with a seismic vibrator to generate polarized vertical and horizontal components along a surface seismic line and an array of 3C geophones cemented outside the casing. The recorded traces are processed to obtain virtual sources in the borehole and to simulate single‐well gathers with a variable source‐receiver offset in the vertical array. We compare the results obtained by processing the field data with synthetic signals calculated by numerical simulation and analyse the signal bandwidth and amplitude versus offset to evaluate near‐field effects in the virtual signals. The application provides direct and reflected signals with improved bandwidth after vibrator signal deconvolution. Clear reflections are detected in the virtual seismic sections in agreement with the geology and other surface and borehole seismic data recorded with conventional seismic exploration techniques. 相似文献
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A methodology for seismic microzonation and earthquake damage scenarios may be considered as composed of two stages. In the first stage, microzonation maps with respect to estimated earthquake characteristics on the ground surface are generated for an investigated urban area. The effects of local geological and geotechnical site conditions are taken into account based on site characterization with respect to representative soil profiles extending down to the engineering bedrock. 1D site response analyses are performed to calculate earthquake characteristics on the ground surface using as many as possible, hazard compatible real acceleration time histories. In the second stage, vulnerability of buildings and pipeline systems are estimated based on site-specific ground motion parameters. A pilot study is carried out to evaluate seismic damage in a district in Istanbul, Turkey. The results demonstrate the significance of site characterization and site response analysis in calculating the earthquake characteristics on the ground surface in comparison to simplified empirical procedures. 相似文献
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当前,合理确定地震动峰值加速度与反应谱特征周期是工程场地地震动参数确定工作的主要内容。本文以北京地区典型中硬场地为研究对象,分析场地条件对不同周期地震动反应谱值的影响。首先,计算不同震级、震中距条件下的基岩地震动加速度反应谱,合成基岩输入地震动时程;再利用110个工程场地的钻孔资料进行土层地震反应计算,分析中硬场地条件对不同输入环境下的地震动加速度反应谱值的放大效应。结果表明,中硬场地对高、中频震动放大效应明显,尤其是对0.2-0.5s周期段地震动加速度反应谱值的放大倍数大多在1.3以上;场地覆盖层厚度变化对不同频段地震动加速度反应谱值的放大倍数所产生的影响是不同的,与场地自振周期的相关性很强;在不同的地震动输入环境下,中硬场地对不同频段地震动加速度反应谱的影响是不同的,这一结论对实际的抗震设防工作具有一定参考价值。 相似文献
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随着强震台网的密布及观测记录的增加,为研究各类局部场地地震反应预测模型的合理性提供了有效的参考依据,也使利用强震记录及场地条件研究地震动特征成为可能。选取场地地质参数资料和地震记录数据齐全的日本小田原（Ashigara Valley）盲测试验场地,通过对比不同地震动输入方式及场地反应分析模型,研究地震动特征,分析现有模型的优劣。基于1990年8月5日M5.1强震事件的地表基岩记录和地下基岩地震记录,采用地下台强震记录直接输入、地表基岩台强震记录减半为基底地震动输入、地表基岩台强震记录反演为基底地震动输入作为3种基岩地震动输入。基于局部场地条件分别建立一维等效线性模型、二维黏弹性模型及二维时域等效线性化模型等工程中常用的场地数值分析模型,进行局部场地地震反应分析,预测该盲测场地的地表地震动特征,并与对应的实测强震记录结果进行对比,分析不同基岩地震动输入方式对预测地震动特征及地表土层反应谱特征的影响,重点分析地震动输入、土体非线性、场地横向不均匀性及几何与非线性特征共同作用等因素对地表地震动特征的影响,以期为地表地震动的合理预测提供参考。 相似文献
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南京河西地区设计地震动研究 总被引：7，自引：3，他引：4
本文根据南京及周围地区的地震环境,采用概率法对南京河西地区某高层公寓工程场址进行了地震危险性分析,采用等效线性化模型考虑场地土的非线性特性的影响,并用一维波动模型进行了场址土层地震反应和场地地震动效应分析,给出了５０年超越概率６３％,１０％和３％的场址基岩和地表的水平向加速度反应谱值加速度。 相似文献
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R. Maresca M. Castellano R. De Matteis G. Saccorotti P. Vaccariello 《Pure and Applied Geophysics》2003,160(9):1745-1764