On a modal damping identification model for non-classically damped linear building structures subjected to earthquakes     

George A. Papagiannopoulos  Dimitri E. Beskos 《Soil Dynamics and Earthquake Engineering》2009

A simple modal damping identification model developed by the present authors for classically damped linear building frames is extended here to the non-classically damped case. The modal damping values are obtained with the aid of the frequency domain modulus of the roof-to-basement transfer function and the resonant frequencies of the structure (peaks of the transfer function) as well as the modal participation factors and mode shapes of the undamped structure. The assumption is made that the modulus of the transfer function of the non-classically damped structure matches the one of the classically damped structure in a discrete manner, i.e., at the resonant frequencies of that function modulus. This proposed approximate identification method is applied to a number of plane building frames with and without pronounced non-classical damping under different with respect to their frequency content earthquakes and its limitations and range of applicability are assessed with respect to the accuracy of both the identified damping ratios and that of the seismic structural response obtained by classical mode superposition and use of those identified modal damping ratios.  相似文献   

Interaction of Tectonic and Surface Geological Processes     

Paul T. Robinson Department of Earth Sciences  Dalhousie University  Canada 《Continental Dynamics》2000,(1)

1. Introduction to surface processesThe shape or morphology of Earth's surface is basically the result of the interplay between two competing forces - mountain building and erosion. Tectonic forces, driven by thermal energy from Earth's interior, cause the rocks of the crust to be folded, faulted and uplifted into high plateaus and mountain belts. As soon as uplift begins, the processes of erosion, driven by gravity, start to wear away the rocks. Masses of weathered rock move downhill under t…  相似文献   

Characterization of seismic hazard and structural response by energy flux     

E. afak 《Soil Dynamics and Earthquake Engineering》2000,20(1-4)

Seismic safety of structures depends on the structure's ability to absorb the seismic energy that is transmitted from ground to structure. One parameter that can be used to characterize seismic energy is the energy flux. Energy flux is defined as the amount of energy transmitted per unit time through a cross-section of a medium, and is equal to kinetic energy multiplied by the propagation velocity of seismic waves. The peak or the integral of energy flux can be used to characterize ground motions. By definition, energy flux automatically accounts for site amplification. Energy flux in a structure can be studied by formulating the problem as a wave propagation problem. For buildings founded on layered soil media and subjected to vertically incident plane shear waves, energy flux equations are derived by modeling the building as an extension of the layered soil medium, and considering each story as another layer. The propagation of energy flux in the layers is described in terms of the upgoing and downgoing energy flux in each layer, and the energy reflection and transmission coefficients at each interface. The formulation results in a pair of simple finite-difference equations for each layer, which can be solved recursively starting from the bedrock. The upgoing and downgoing energy flux in the layers allows calculation of the energy demand and energy dissipation in each layer. The methodology is applicable to linear, as well as nonlinear structures.  相似文献   

中国近期强震与天体的特殊位置关系分析     

徐秀登  俞孟浩  李晓明 《天文研究与技术》2000,(3):55-66

通过统计分析 1 990～ 1 998年中国Ms≥ 6级地震与太阳系主要天体的特殊位置的关系 ,说明两者具有较好的相关性。我们可以在此基础上 ,结合其它预报手段 ,对中国地震进行预测  相似文献   

Anomalous behaviour of precursor resistivity in Shillong area, NE India     

J. R. Kayal  B. Banerjee 《Geophysical Journal International》1988,94(1):97-103

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Liquefaction potential of Quaternary alluvium in Bolu settlement area,Turkey   总被引：1，自引：0，他引：1  

Koray Ulamis  Recep Kilic 《Environmental Geology》2008,55(5):1029-1038

Groundwater bearing alluvial units in the seismically active settlement areas may bring out probable damage on the urban and built environment due to liquefaction. Bolu settlement area and surroundings are located in the North Anatolian Fault Zone. Geotechnical boreholes were drilled in order to determine the distribution of the geological units, to obtain representative soil samples and to measure groundwater level. Quaternary aged alluvium is the main geological unit in the South of study area. Stiffness and consistency of the soils were determined by Standart penetration test. P and S wave velocities of soil have been measured along the seismic profiles. The index and physical properties of the samples have also been tested in the laboratory. Liquefaction potential and safety factor of the sandy levels in Quaternary aged alluvium were investigated by different methods based on SPT and V _s. Liquefaction seems to be a significant risk in case of an earthquake with a _max = 0.48 g and M _w = 7.5 at different levels of the boreholes. This situation may bring out environmental problems in the future.  相似文献   

Sources of M_w 5+ earthquakes in northeastern Italy and western Slovenia: An updated view based on geological and seismological evidence     

Pierfrancesco Burrato  Maria Eliana Poli  Paola Vannoli  Adriano Zanferrari  Roberto Basili  Fabrizio Galadini 《Tectonophysics》2008,453(1-4):157

We present an overview of the seismogenic sources of northeastern Italy and western Slovenia, included in the last version of the Database of Individual Seismogenic Sources (DISS 3.0.2) and a new definition of the geometry of the Montello Source that will be included in the next release of the database. The seismogenic sources included in DISS are active faults capable of generating M_w > 5.5 earthquakes. We describe the method and the data used for their identification and characterization, discuss some implications for the seismic hazard and underline controversial points and open issues.In the Veneto–Friuli area (NE Italy), destructive earthquakes up to M_w 6.6 are generated by thrust faulting along N-dipping structures of the Eastern Southalpine Chain. Thrusting along the mountain front responds to about 2 mm/a of regional convergence, and it is associated with growing anticlines, tilted and uplifted Quaternary palaeolandsurfaces and forced drainage anomalies. In western Slovenia, dextral strike–slip faulting along the NW–SE trending structures of the Idrija Fault System dominates the seismic release. Activity and style of faulting are defined by recent earthquakes (e.g. the M_s 5.7, 1998 Bovec–Krn Mt. and the M_w 5.2, 2004 Kobarid earthquakes), while the related recent morphotectonic imprint is still a debated matter.We reinterpreted a large set of tectonic data and developed a segmentation model for the outermost Eastern Southalpine Chain thrust front. We also proposed the association of the four major shocks of the 1976 Friuli earthquake sequence with individual segments of three major thrust fronts. Although several sub-parallel active strike–slip strands exist in western Slovenia, we were able to positively identify only two segments of the Idrija Fault System. A comparison of the regional GPS velocity with long-term geological slip-rates of the seismogenic sources included in DISS shows that from a quarter to half of the deformation is absorbed along the external alignment of thrust faults in Veneto and western Friuli. The partitioning of the deformation in western Slovenia among the different strike–slip strands could not be quantified.  相似文献   

相继发生的三个强震的分布关系   总被引：5，自引：0，他引：5  

邓志辉  马瑾 《地震地质》1991,13(2):173-178

本文从动态的观点出发,把时间上相继发生的三个7级以上强震(设它们分别为A、B和C事件)在空间上的分布关系作为主要研究内容。研究结果表明:(1)ABC所在平面的优势分布是切过软流圈的顶部或岩石圈的下部;(2)在地震A和B发生之后,地震C的优势分布是位于A,B连线的延伸部分和A,B之间稍近A的部位。根据A,B,C的分布关系,结合各地区的地质条件和历史地震资料等,我们可以从已知的两个7级以上强震预测第三个7级以上强震在各地区的发震概率大小  相似文献   

A closing Ligurian Sea?     

N. Bethoux  J. Fréchet  F. Guyoton  F. Thouvenot  M. Cattaneo  C. Eva  M. Nicolas  M. Granet 《Pure and Applied Geophysics》1992,139(2):179-194

Two earthquakes occurred in the Ligurian Sea in December 1989 and April 1990. Both were widely felt along the French and Italian Rivieras, thus reminding us of the seismic risk in this region. The significant increase in the number of seismic stations in the area facilitated the study of these two shocks and their related aftershocks. Using different techniques (absolute and relative hypocentral locations, doublet analysis and waveform modeling), we computed accurate hypocentral locations and estimated the location-error range for earthquakes in this area. We also computed the focal mechanisms for both mainshocks, and we present here a synthesis that integrates previous data. The reactivation in compression of the Ligurian Sea sphenochasm is confirmed, which would eventually result in the closing of an aborted oceanic domain. As the seismic activity is clearly restricted to the northern margin, we suggest it locally results from the lateral expulsion of the south-western Alps along the Apulian indenter.  相似文献   

重庆市江北5.2,5.4级地震的地质构造背景   总被引：2，自引：0，他引：2  

江北地震宏观考察组 《四川地震》1992,(3):59-64

1989年11月20日的重庆市江北5.2级、5.4级地震。被认为是处于四川东部台拗的一系列线状、弧形状构造在现代近东西向应力作用下,这一发育极为完整的构造再次活动的结果。其具体背景构造有华蓥山构造带、七曜山—金佛山构造带和长寿—南桐构造带。它们是该区中强地震的直接控震构造。这些构造带控制了该区的岩性、构造和应力的积累、释放。故认为地震的发生正是上述构造带相继多次活动,从而导致江北地区地腹构造发生粘滑性活动的结果。  相似文献