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1.
Vladimir Yu Sokolov Friedemann Wenzel Rakesh Mohindra 《Soil Dynamics and Earthquake Engineering》2009
The earthquake risk on Romania is one of the highest in Europe, and seismic hazard for almost half of the territory of Romania is determined by the Vrancea seismic region, which is situated beneath the southern Carpathian Arc. The region is characterized by a high rate of occurrence of large earthquakes in a narrow focal volume at depth from 70 to 160 km. Besides the Vrancea area, several zones of shallow seismicity located within and outside the Romanian territory are considered as seismically dangerous. We present the results of probabilistic seismic hazard analysis, which implemented the “logic tree” approach, and which considered both the intermediate-depth and the shallow seismicity. Various available models of seismicity and ground-motion attenuation were used as the alternative variants. Seismic hazard in terms of macroseismic intensities, peak ground acceleration, and response spectra was evaluated for various return periods. Sensitivity study was performed to analyze the impact of variation of input parameters on the hazard results. The uncertainty on hazard estimates may be reduced by better understanding of parameters of the Vrancea source zone and the zones of crustal seismicity. Reduction of uncertainty associated with the ground-motion models is also very important issue for Romania. 相似文献
2.
Xiaowu Pu Lanming Wang Ping Wang Xiufeng Tian Shiyang Xu Shaofeng Chai Haitao Guo 《地震研究进展（英文）》2022,2(3):100114
A series of housing collapses and other serious damage was caused by the 2008 Wenchuan MS 8.0 earthquake in the seismic intensity Ⅵ areas of the Loess Plateau, which is hundreds of kilometers away from the epicenter, and which showed a remarkable seismic intensity anomaly. The seismic disasters are closely related to the seismic response characteristics of the site, therefore, the systematic study of the far-field seismic response law of the Wenchuan earthquake in the Loess Plateau is of great significance to prevent the far-field disaster of great earthquake. In this paper, the seismic acceleration records of several bedrock stations and loess stations from the seismogenic fault of the Wenchuan earthquake to the Loess Plateau were collected, and the attenuation law of ground motion along the propagation path and the characteristics of seismic response on the loess site are studied, and the mechanism of amplification effect of ground motion is analyzed based on the dynamic feature parameters of the loess site obtained through the HVSR method. Taking a typical loess site of thick deposit as the prototype, a series of shaking table tests of dynamic response of loess site models with different thicknesses were carried out. Amplification effect, spectral characteristics of acceleration in model sites were analyzed under the action of a far-field seismic wave of the Wenchuan earthquake. The results show that seismic attenuation on the propagation path along the NE strike of the seismogenic fault to the Loess Plateau is slower than that in other directions, and the predominant period range of ground motion on bedrock site of the Loess Plateau presents broadband characteristics. Because the natural periods of loess sites with thick deposits are within the predominant period range of bedrock input wave, loess sites appear significant amplification effect of ground motion, the horizontal acceleration of ground motion exceeds 0.1 ?g, the seismic intensity reaches 7°. The thicker the loess deposit is, the more significant the change of spectral characteristics of ground motion on loess sites, and the narrower the predominant period range of ground motion becomes, and the closer it is to the natural period of loess sites. Therefore, for some old houses on thick loess sites, the poor seismic performance and strong seismic response eventually led to their collapses and damages because their natural periods are very close to the predominant period of ground motion of the Wenchuan earthquake on thick loess sites; For these damaged high-rise buildings, the resonance effect might be the main reason for their damages because their natural periods are included in the predominant period range of ground motion of the Wenchuan earthquake on thick loess sites.These research results would provide a basis for seismic disasters prediction and evaluation and seismic design of construction engineering in the Loess Plateau. 相似文献
3.
Radu Vacareanu Florin Pavel Ionut Craciun Veronica Coliba Cristian Arion Alexandru Aldea Cristian Neagu 《Journal of Seismology》2018,22(2):407-417
Romania has one of the highest seismic hazard levels in Europe. The seismic hazard is due to a combination of local crustal seismic sources, situated mainly in the western part of the country and the Vrancea intermediate-depth seismic source, which can be found at the bend of the Carpathian Mountains. Recent seismic hazard studies have shown that there are consistent differences between the slopes of the seismic hazard curves for sites situated in the fore-arc and back-arc of the Carpathian Mountains. Consequently, in this study we extend this finding to the evaluation of the probability of collapse of buildings and finally to the development of uniform risk-targeted maps. The main advantage of uniform risk approach is that the target probability of collapse will be uniform throughout the country. Finally, the results obtained are discussed in the light of a recent study with the same focus performed at European level using the hazard data from SHARE project. The analyses performed in this study have pointed out to a dominant influence of the quantile of peak ground acceleration used for anchoring the fragility function. This parameter basically alters the shape of the risk-targeted maps shifting the areas which have higher collapse probabilities from eastern Romania to western Romania, as its exceedance probability increases. Consequently, a uniform procedure for deriving risk-targeted maps appears as more than necessary. 相似文献
4.
5.
Local site conditions can significantly influence the characteristics of seismic ground motions. In this study, site response analyses using one-dimensional linear elastic (LE), equivalent-linear (EQL) and nonlinear (NL) approaches are performed at different seismic hazard levels of Singapore. Two seismic stations, namely, the KAP and BES stations located at soft soil sites, are selected from the national network of Singapore. Firstly, site response estimates using the LE, EQL (SHAKE04) and NL (DEEPSOIL) approaches are compared with the borehole recordings. Results show favorable matches between the predictions and the observations at the KAP site, while under-predictions are observed for all the three site effect approaches at the BES site. Secondly, the applicability of the LE, EQL and NL models is examined at different hazard levels of Singapore. It is found that for the hazard level at a return period of 475 years, the computed maximum strain (γmax) is 0.06% and then the EQL model can provide accurate site response predictions. However, for the hazard level at a return period of 2475 years, the calculated γmax is larger than 2%, resulting in notable differences in the predictions of different site response models. This study highlights the importance of site effects in seismic hazard analysis of Singapore. 相似文献
6.
选取2008年5月25日至8月7日期间由甘肃省文县上城山地形效应台阵获取的12次汶川地震余震事件(MS≥4.0),在分析其地震动基本参数的基础上,采用参考场地谱比(RSSR)法和水平-竖向谱比(HVSR)法,研究了不同地震作用下上城山地形台阵的场地效应.分析结果显示:随着高程和覆盖层的增加,记录台站地震动的PGA呈增大趋势,地震频谱形状由宽变窄;上城山台阵记录到的地震波在地形基阶频段(2—4 Hz)和浅部土层频段(7—9 Hz)的幅值明显放大,RSSR曲线显示山顶NS向的土层频段谱比大于山体地形频段谱比;由于土层山体竖向地震动在中高频段放大,使得HVSR方法谱比结果在中高频段较RSSR方法所得结果明显偏低,而在山体基阶频段附近两种方法的谱比值接近.松散土层山体的台阵记录特征体现了地形和土层对地震动的联合作用,揭示了强震区起伏地形场地震害加重及地震滑坡集中发生的原因所在. 相似文献
7.
The seismic vulnerability index(Kg) is a parameter that depends on the dynamic properties of soil. With this parameter, it is possible to evaluate the vulnerability of a point-based site under strong ground motion. Since it is related to the natural vibration period and amplification factor, the parameter can be calculated for both soil and structure. In this study, HVSR microtremor measurements are recorded at more than 200 points in the Van region to generate a seismic vulnerability index map. After generating the map, it is determined that the hazard potential and seismic vulnerability index is high at the sites close to Van Lake and at the densely populated city center. Damage information of the buildings investigated after the 2011 Van earthquakes(Mw = 7.1) are placed on the seismic vulnerability index map and it is realized that there may be a correlation between the damage and the seismic vulnerability index. There is a high correlation, approximately 80 percent, between the damage rate map based on the damaged building data and the K_g values. In addition, vulnerability indexes of buildings are calculated and the effect of local soil conditions and building properties on the damage levels are determined. From the results of this study and the site observations after the 2011 Van earthquakes, it is found that structural damage is not only structure-dependent but is also related to the dynamic behavior of soil layers and local soil conditions. 相似文献
8.
Ruifang Yu Yisheng Song Xiangyun Guo Qianli Yang Xinjuan He Yanxiang Yu 《地震科学（英文版）》2022,35(5):314-328
Seismic hazard analyses are mainly performed using either deterministic or probabilistic methods. However, there are still some defects in these statistical model-based approaches for regional seismic risk assessment affected by the near-field of large earthquakes. Therefore, we established a deterministic seismic hazard analysis method that can characterize the entire process of ground motion propagation based on stochastic finite-fault simulation, and we chose the site of the Xiluodu dam to demonstrate the method. This method can characterize earthquake source properties more realistically than other methods and consider factors such as the path and site attenuation of seismic waves. It also has high computational efficiency and is convenient for engineering applications. We first analyzed the complexity of seismogenic structures in the Xiluodu dam site area, and then an evaluation system for ground motion parameters that considers various uncertainties is constructed based on a stochastic finite-fault simulation. Finally, we assessed the seismic hazard of the dam site area comprehensively. The proposed method was able to take into account the complexity of the seismogenic structures affecting the dam site and provide multi-level parameter evaluation results corresponding to different risk levels. These results can be used to construct a dam safety assessment system of an earthquake in advance that provides technical support for rapidly and accurately assessing the post-earthquake damage state of a dam, thus determining the influence of an earthquake on dam safety and mitigating the risk of potential secondary disasters. 相似文献
9.
局部场地条件是决定场地地震动强度和频谱的重要因素，基于强震动和脉动记录的统计分析，获取表征场地条件影响的特征参数已成为确定工程场地设计地震动的较经济和实用方法，特别是对于大范围或难以开展现场勘测的工程场地。利用日本KiK-net台网强震动记录计算分析了台站场地地震动水平/竖向谱比（HVSR）与地表/基底谱比（SBSR）的差异，揭示SBSR/HVSR与HVSR呈对数线性分布的统计特征，并给出其定量关系，据此提出表征场地对地震动影响的修正水平/竖向谱比法。修正水平/竖向谱比法具有仅需地表观测记录的优势，并进一步考虑了场地竖向地震效应对水平/竖向谱比法精度的影响，更能合理地表征场地对地震动的影响。 相似文献
10.
Empirical correlations between response spectra, magnitude, distance from the source and geological site conditions are introduced in a regional study of seismic hazard. A 350-year earthquake catalogue is treated by means of the statistics of extremes and both the spectral amplitudes (pseudovelocity) corresponding to a series of frequency bands are separately mapped, and the complete predicted response spectra calculated at some sites. Three kinds of geological site conditions are considered: thick and thin (less than 20 m deep) alluvium, and rock. A particular dependence of the results on the geographical distribution of earthquakes and on their magnitudes is commented. The seismic hazard of the study area is also computed by applying a traditional regression between peak ground velocity, magnitude and distance; a comparison with the seismic hazard given by the frequency dependent psuedovelocity indicates the extent of the uncertainty associated with the common practice of scaling response spectra directly from ground motion parameters. 相似文献
11.
The characteristics of seismic ground motions in southern China are difficult to determine statistically due to a lack of strong ground motion data. In this study, a stochastic finite-fault ground motion model was adopted to simulate the seismic ground motions at bedrock for southern China, based on parameters derived from small and medium earthquakes that have occurred in the region. From these, the response spectra was estimated. A set of ground motion attenuation relationships was then developed based on simulated peak ground motions and response spectral parameters through regression, which would be applicable for use in engineering practice. Through comparisons, it was demonstrated that the proposed ground motion relationships are generally consistent with those obtained from other reported ground motion attenuation models for southern China. 相似文献
12.
Subhadra Nampally Simanchal Padhy S. Trupti P. Prabhakar Prasad T. Seshunarayana 《Journal of Seismology》2018,22(4):1075-1093
We study local site effects with detailed geotechnical and geophysical site characterization to evaluate the site-specific seismic hazard for the seismic microzonation of the Chennai city in South India. A Maximum Credible Earthquake (MCE) of magnitude 6.0 is considered based on the available seismotectonic and geological information of the study area. We synthesized strong ground motion records for this target event using stochastic finite-fault technique, based on a dynamic corner frequency approach, at different sites in the city, with the model parameters for the source, site, and path (attenuation) most appropriately selected for this region. We tested the influence of several model parameters on the characteristics of ground motion through simulations and found that stress drop largely influences both the amplitude and frequency of ground motion. To minimize its influence, we estimated stress drop after finite bandwidth correction, as expected from an M6 earthquake in Indian peninsula shield for accurately predicting the level of ground motion. Estimates of shear wave velocity averaged over the top 30 m of soil (VS30) are obtained from multichannel analysis of surface wave (MASW) at 210 sites at depths of 30 to 60 m below the ground surface. Using these VS30 values, along with the available geotechnical information and synthetic ground motion database obtained, equivalent linear one-dimensional site response analysis that approximates the nonlinear soil behavior within the linear analysis framework was performed using the computer program SHAKE2000. Fundamental natural frequency, Peak Ground Acceleration (PGA) at surface and rock levels, response spectrum at surface level for different damping coefficients, and amplification factors are presented at different sites of the city. Liquefaction study was done based on the VS30 and PGA values obtained. The major findings suggest show that the northeast part of the city is characterized by (i) low VS30 values (<?200 m/s) associated with alluvial deposits, (ii) relatively high PGA value, at the surface, of about 0.24 g, and (iii) factor of safety and liquefaction below unity at three sites (no. 12, no. 37, and no. 70). Thus, this part of the city is expected to experience damage for the expected M6 target event. 相似文献
13.
Jorge M. Gaspar-Escribano Manuel Navarro Belén Benito Antonio García-Jerez Francisco Vidal 《Bulletin of Earthquake Engineering》2010,8(6):1547-1567
An approach that relates results from a regional seismic hazard assessment study with local-scale site-effect characterizations
in an area of low-to-moderate seismic activity such as Andalusia (southern Spain), is presented. Results of a previous probabilistic
seismic hazard analysis of Andalusia on rock conditions are disaggregated to infer hazard controlling earthquakes for different
target motions. A collection of controlling magnitude-distance pairs and the corresponding site-specific response spectra
at main capital cities of the region are obtained. These spectra are first-order approximations to expected seismic actions
required in local earthquake risk assessments. In addition, results of independent, local-scale studies developed in Almeria
City (SE Andalusia) are used to derive an updated seismic zonation of the city. These include predominant soil period estimates
and shear-wave velocity profiles at different locations. If a local seismic risk assessment study or an earthquake-resistant
structural design is to be developed, it may be recommended the use of different seismic actions on sites characterized by
distinct response to seismic shaking (as derived from the seismic zonation). The seismic action related to worst-case scenarios
may be modeled through a hazard-consistent response spectrum, obtained by hazard disaggregation at the spectral acceleration
with period matching the prevailing resonant period of the target site or structure. 相似文献
14.
Evaluation of the seismic hazard for 20 cities in Romania using Monte Carlo based simulations 总被引：2，自引：0，他引：2
This work focuses on the evaluation of the seismic hazard for Romania using earthquake catalogues generated by a Monte Carlo approach. The seismicity of Romania can be attributed to the Vrancea intermediate-depth seismic source and to 13 other crustal seismic sources. The recurrence times of large magnitude seismic events (both crustal and subcrustal), as well as the moment release rates are computed using simulated earthquake catalogues. The results show that the largest contribution to the overall moment release for the crustal seismic sources is from the seismic regions in Bulgaria, while the seismic regions in Romania contribute less than 5% of the overall moment release. In addition, the computations show that the moment release rate for the Vrancea subcrustal seismic source is about ten times larger than that of all the crustal seismic sources. Finally, the Monte Carlo approach is used to evaluate the seismic hazard for 20 cities in Romania with populations larger than 100,000 inhabitants. The results show some differences between the seismic hazard values obtained through Monte-Carlo simulation and those in the Romanian seismic design code P100-1/2013, notably for cities situated in the western part of Romania that are influenced by local crustal seismic sources. 相似文献
15.
Temporal changes in site effects are obtained using the HVSR(horizontal-to-vertical spectral ratio) method and strong motion records after the M w 7.6 Chi-Chi earthquake, Taiwan. Seismic data recorded between 1995 and 2010 are used, comprising 3,708 data from 15 stations adjacent to the Chelungpu fault. Temporal fl uctuations are determined by analyzing the site effect variation using a time–frequency variation(TFV) diagram based on these seismic data. Stations adjacent to the fault show signifi cant disturbances in the resonance frequency at 16–26 Hz. Station TCU129 shows a 40% drop in fundamental frequency after the main shock, and a gradual return to the original state over nine years. For stations located farther from the fault zone, sudden changes in tectonic stress play a dominant role in temporal changes to the HVSR. An impact analysis of the directional factor confi rms our fi nding that the proximity of the fault to seismic stations has the most infl uence on data. 相似文献
16.
通过布置于龙门山断裂带中段、龙门山山前玉皇观区域的地震观测台站阵列接收地震数据,研究该区域的地震动放大效应和地下地质结构.观测阵列共10台宽频带地震仪,分布在玉皇观河口冲积扇区域.分别采用参考场址谱比法(RSSR)和HV谱比法(HVSR)计算64个高信噪比近震数据的振幅谱比函数,结果显示在玉皇观区域具有较明显的地震动放大效应,并且局部场址效应显著.以S06场址为例,建立近地表地震地质模型,通过SH波放大效应正演模拟研究该场址的地震动放大模式.RSSR与HVSR的结果表明,两者所计算的场址放大效应主频一致,但是HVSR的放大峰值却比RSSR的放大峰值大一倍左右,表明HVSR的结果可能包含了波场在近地表低速层之下传播路径的改造作用.另外,采用27个远震P波的接收函数计算了该区域地壳上地幔S波速度结构.接收函数研究结果显示玉皇观地区的莫霍面深度为44 km,沉积盖层、结晶地壳和上地幔的S波速度分别为2.5 km·s~(-1)、3.5 km·s~(-1)和4.5 km·s~(-1).观测阵列台站之间的接收函数反演结果一致性较好,说明本研究区域范围内地形地貌等近地表结构因素的相对变化对接收函数的影响不大. 相似文献
17.
V. I. Ulomov 《Izvestiya Physics of the Solid Earth》2010,46(1):1-18
According to the normative maps of the General Seismic Zoning in the Russian Federation, OSR-97, the Moscow metropolitan area
is situated within the 5 point seismic zone. Of highest hazard priority for tall buildings in Moscow are the low-frequency
vibrations proceeding from the deep sources of strong earthquakes that occur in the East Carpathians (the Vrancea zone, Romania)
at a distance of approximately 1350 km from Moscow. Accelerations of the ground vibrations in Moscow are found from the analysis
of seismic signals produced by Mw = 5.0 to Mw = 7.4 Vrancea earthquakes and recorded at the Moskva seismic station. Extrapolation of the parameters of the weak and moderate
earthquakes towards stronger seismic events provides an estimate for the maximum expected horizontal accelerations of Ahor = 2.3 cm/s2 in case of the Mw = 8.0 Vrancea earthquake. The synthetic accelerogram of the maximum possible effect on the benchmark soils of Moscow is calculated.
The displacements of the ground are multidimensional and not necessarily oriented strictly towards the seismic source. These
inferences suggest that the MSK-64 macroseismic scale be corrected and the Construction Norms and Regulations, SNIP II-7-81*,
be updated with regard to the hazard assessment of low-frequency seismic effects of 5 point and weaker seismic events including
those caused by distant earthquakes. 相似文献
18.
Site response in the Qionghai Basin in the Wenchuan earthquake 总被引：2，自引：1，他引：1
Amplification effects of soil site response can significantly impact ground motions, and must be considered in the seismic fortification of buildings/structures to prevent or mitigate this potential seismic hazard. Utilizing acceleration time histories from the main shock of the Wenchuan earthquake recorded at four stations (i.e., one on bedrock and three on soil) in the Qionghai Basin, the site responses from three soil sites are studied by using the traditional spectral ratio method. The bedrock site is selected as a reference site. This study found that peak ground accelerations (PGAs) on the soil sites are much larger than on bedrock, with EW, NS and UD components of 3.96–6.58, 6.27–10.98, and 3.17–6.66 times those of the bedrock site, respectively. The amplification effects of the soil sites on ground motions in the frequency range of 0.1 Hz to 10 Hz are significant, depending on the thickness of the soil layer and the frequency content of the site. A significant amplification occurs with high frequency components of ground motion at shallow soil sites, and low and high frequency components of ground motion at intermediate soil sites. 相似文献
19.
This paper aims at investigating possible regional attenuation patterns in the case of Vrancea(Romania) intermediate-depth earthquakes.Almost 500 pairs of horizontal components recorded during 13 intermediate-depth Vrancea earthquakes are employed in order to evaluate the regional attenuation patterns.The recordings are grouped according to the azimuth with regard to the Vrancea seismic source and subsequently,Q models are computed for each azimuthal zone assuming similar geometrical spreading.Moreover,the local soil amplification which was disregarded in a previous analysis performed for Vrancea intermediate-depth earthquakes is now clearly evaluated.The results show minor differences between the four regions situated in front of the Carpathian Mountains and considerable differences in attenuation of seismic waves between the forearc and backarc regions(with regard to the Carpathian Mountains).Consequently,an average Q model of the type Q(f) = 115×f~(1.25) is obtained for the four forearc regions,while a separate Q model of the type Q(f) = 70×f~(0.90) is computed for the backarc region.These results highlight the need to evaluate the seismic hazard of Romania by using ground motion models which take into account the different attenuation between the forearc/backarc regions. 相似文献
20.
L. Peruzza A. Rebez D. Slejko P. L. Bragato 《Soil Dynamics and Earthquake Engineering》2000,20(5-8):361-371
Probabilistic seismic hazard maps, in terms of spectral acceleration and uniform hazard response spectra at given sites, considering local soil conditions, represent a much more complete estimate of the seismic hazard than the traditional maps in terms of peak ground acceleration or macroseismic intensity. This is particularly true when the requests of urban planners and engineers have to be met. The present analysis shows how some hazard parameters, such as the effective peak acceleration and the spectrum intensity, can well synthesise the overall information available from traditional probabilistic studies, but also suggests that soil condition is a first-order ingredient for effective seismic hazard mapping at national level. Three Italian towns, damaged by the 1997 Umbria–Marche earthquake sequence, are considered as example to demonstrate that: (1) soil condition dependent uniform hazard spectra well approximate actual spectra recorded during some events of the seismic sequence; (2) for these localities, the design spectrum of the present Italian seismic code does not seem adequate.
These considerations have induced the Italian scientific community to propose an updating of the national seismic zonation on the basis of several hazard parameters, that are described in this paper. 相似文献