A new method for non‐stationary random critical excitation     

Izuru Takewaki 《地震工程与结构动力学》2001,30(4):519-535

Since earthquake ground motions are very uncertain even with the present knowledge, it is desirable to develop a robust structural design method taking into account these uncertainties. Critical excitation approaches are promising and a new non‐stationary random critical excitation method is proposed. In contrast to the conventional critical excitation methods, a stochastic response index is treated as the objective function to be maximized. The power (area of power spectral density (PSD) function) and the intensity (magnitude of PSD function) are fixed and the critical excitation is found under these restrictions. It is shown that the original idea for stationary random inputs can be utilized effectively in the procedure for finding a critical excitation for non‐stationary random inputs. The key for finding the new non‐stationary random critical excitation is the exchange of the order of the double maximization procedures with respect to time and to the power spectral density function. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Derivation of design soil coefficients (S) and response spectral shapes for Eurocode 8 using the European Strong-Motion Database   总被引：1，自引：0，他引：1  

Julien Rey  Ezio Faccioli  Julian J. Bommer 《Journal of Seismology》2002,6(4):547-555

A revision is presently under way to upgrade the status of the `Designrecommendations for earthquake resistance of structures', commonlyreferred to as Eurocode 8 (or EC8). In order to improve the definition ofthe design elastic response spectra (ERS) as defined in the Eurocode 8 –Part 1 (Draft May 2001), the values of the soil amplification factors havebeen calculated for sites on sedimentary soils, both stiff (category B) andsoft (category C), with respect to rock sites (category A), such ascontemplated in EC8. The work was performed by a systematic study ofresponse spectra as a function of magnitude and site conditions, usingrecords from the European Strong-Motion Database.The results confirm the occurrence of systematic spectral amplification onsedimentary soils with respect to reference rock in a large set of Europeanstrong motion data. Such amplification has been quantified through ameasure derived from the Housner Spectrum Intensity definition.The values of the soil coefficients recommended in the current version ofEC 8 are shown to be realistic for category C, in the case of a moderateseismicity context. However the values for subsoil class B need to besignificantly increased both for the moderate and high seismicity context.  相似文献   

Frequency dependence of seismic wave attenuation in the upper mantle beneath the Australian region     

H.-X. Cheng  B. L. N. Kennett 《Geophysical Journal International》2002,150(1):45-57

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厄尔尼诺年和反厄尔尼诺年北半球500hPa非绝热热流量场的特征     

章基嘉  李跃清  雷兆崇  孙照渤 《南京气象学院学报》1991,(3)

本文应用谱方法,诊断、计算了1964—1985年间,6个厄尔尼诺年和6个反厄尔尼诺年北半球月、季大气非绝热热流量距平场。结果表明:厄尔尼诺现象对大气非绝热热流量距平场具有显著影响,大气的响应表现为低纬和中高纬非绝热热流量正负距平中心有组织的优势排列,其位相或强度存在低频振荡,并且差值中心表现为双月周期。反厄尔尼诺年,大气具有分布不变,但距平中心基本上为反位相的响应形式。最后,通过海气相关分析,指出了海温异常是决定大气非绝热热流量异常的最重要的原因。  相似文献   

彩红外航空像片应用于森林灾害调查的方法与结果分析     

唐小平 《遥感学报》1991,(1)

本文应用联邦德国的一个实例,介绍了大比例尺(1:5000)彩红外航空像片应用于森林灾害调查的程序和方法。总结了彩红外航空像片判读树种和林木受损害等级的标志;并分析了不同树种、年龄和海拔高度等因素对林木受损害程度的影响;最后提出了调查精度。结果表明:利用彩红外航空像片调查林木因大气污染、病虫害、自然灾害等因子影响而受损的程度的方法,可以为合理经营规划森林资源快速提供较精确的信息。  相似文献   

Analysis of magnetic data over part of the Younger Granite Province of Nigeria     

Charles O. Ofoegbu  Karin Hein 《Pure and Applied Geophysics》1991,136(2-3):173-189

The results of a magnetic study of part of the Younger Granite Province of Nigeria are presented here. Spectral analysis of the magnetic anomalies over the area has been carried out in an effort to estimate the depth to magnetic sources. Average magnetic source depth of 286 m has been obtained for the area and this is thought to be related to the depth to the top of the main anomalous structures in the area. Observed magnetic anomaly profiels taken across the area have been interpreted in terms of arbitrarily shaped bodies—whose existence was confirmed by 3-D Hilbert transformation-using nonlinear optimization techniques. The modelled bodies occur at depths of 200–760 m and have magnetizations of 0.29–0.47 A/m. The results from the analysis of the magnetic field are discussed in relation to the results from previous gravity studies over the area and the mode of emplacement of the Younger Granites.  相似文献   

Spanish national strong motion network. Recording of the Huelva earthquake of 20 December, 1989     

E. Carreño  J. Rueda  C. López Casado  J. Galán  J. A. Peláez 《Pure and Applied Geophysics》1991,136(4):395-404

In recent years a network of 30 accelerographs has been installed through the zones of highest seismic activity of Spain. For the first time, digital strong motion records have been obtained in Spain, with a maximum horizontal acceleration value of 0.06 g. A comprehensive study is made of the strong motion recordings of an earthquake which occurred in southwest Spain, on December 20, 1989. The isoseismal map is drawn and the data confirm the main attenuation directions in the area observed in other shocks.  相似文献   

Least-squares collocation, geophysical inverse theory and geostatistics: a bird's eye view   总被引：1，自引：0，他引：1  

Ute Christina Herzfeld 《Geophysical Journal International》1992,111(2):237-249

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WIND WAVES SIMULATION IN THE NORTH AREA OF THE SOUTH CHINA SEA   总被引：1，自引：1，他引：1  

王文质  陈俊昌  黎满球  李毓湘  李志伟 《中国海洋湖沼学报》1992,10(2):107-118

A third generation wave model was developed to simulate wind waves in the South China Sea near Hong Kong. The model solves the energy conservation equation of the two dimensional wave spectrum by directly computing the nonlinear energy interaction among waves of different frequencies, thus avoiding the imposition of restrictions on the shape of the predicted spectra. The use of an upwind difference scheme in the advective terms produces an artificial diffusion which partly compensates the dispersive effect due to the phase velocity differences among various wave components. The use of a semi-implicit scheme for the source terms together with a special treatment of the high frequency tail of the spectrum allows a large time integration step. Verification of the model was done for wave hindcasting studies under conditions of two typhoons and two cold fronts in the north part of the South China Sea near Hong Kong . The model results agree well with the field measurements except that the presence of a dista  相似文献   

三河—平谷地区地脉动H/V谱比法探测:场地响应、浅层沉积结构及其反映的断层活动          下载免费PDF全文

彭菲  王伟君  寇华东 《地球物理学报》1954,63(10):3775-3790

1679年三河—平谷8级地震,造成了包括北京在内的华北广大地区严重的人员和经济损失,但是该地区和地震灾害密切相关的沉积结构和地震场地响应特征研究,相对比较缺乏.本文利用1~4 km台间距的高密度单台地脉动观测、几个小孔径台阵观测和钻孔测井数据,研究了三河—平谷地区的浅层沉积的场地响应和沉积层三维起伏特征,以及构造运动对沉积厚度的影响.结果表明,研究区沉积层的场地共振频率和沉积厚度有明显的分区特征：东北部场地共振频率主要在1.0~7.0 Hz之间,具有相对较薄的沉积厚度,沉积界面起伏也相对平稳;西南部场地共振频率大部分区域小于1.0 Hz,可低至0.3 Hz,相应的沉积厚度起伏显著,其中在大厂凹陷厚度可达300~600 m.沉积起伏和隐伏断裂带的分布有较好的对应关系,反映了夏垫断裂、南苑—通县断裂第四纪以来较为活跃的正断活动.北东走向的夏垫等隐伏断裂在东北部山前的正断活动相对不发育,以及东北部和西南部沉积厚度的显著差异,都可能受到北西走向的二十里长山断裂带活动的影响.按照Vs30场地分类,研究区内沉积较厚的凹陷地区主要为E类软土,其他区域为D类中硬土.研究结果与区域地质调查、钻孔数据和浅层地震勘探剖面结果基本相符,说明地脉动探测方法能够高效、低成本的获取区域沉积厚度和场地作用,为地震小区划和抗震设防提供有意义的参考.  相似文献