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1.
Klaus-G. Hinzen 《Journal of Seismology》2012,16(4):797-814
Vertically oriented objects, such as tombstones, monuments, columns, and stone lanterns, are often observed to shift and rotate during earthquake ground motion. Such observations are usually limited to the mesoseismal zone. Whether near-field rotational ground motion components are necessary in addition to pure translational movements to explain the observed rotations is an open question. We summarize rotation data from seven earthquakes between 1925 and 2009 and perform analog and numeric rotation testing with vertically oriented objects. The free-rocking motion of a marble block on a sliding table is disturbed by a pulse in the direction orthogonal to the rocking motion. When the impulse is sufficiently strong and occurs at the ‘right’ moment, it induces significant rotation of the block. Numeric experiments of a free-rocking block show that the initiation of vertical block rotation by a cycloidal acceleration pulse applied orthogonal to the rocking axis depends on the amplitude of the pulse and its phase relation to the rocking cycle. Rotation occurs when the pulse acceleration exceeds the threshold necessary to provoke rocking of a resting block, and the rocking block approaches its equilibrium position. Experiments with blocks subjected to full 3D strong motion signals measured during the 2009 L’Aquila earthquake confirm the observations from the tests with analytic ground motions. Significant differences in the rotational behavior of a monolithic block and two stacked blocks exist. 相似文献
2.
地震面波产生的地震动转动分量研究 总被引：7，自引：0，他引：7
本文利用弹性波动理论对地面转动分量，即瑞利（Rayleigh)波和乐夫（Love)波产生的转动分量进行了研究，给出了相应的计算公式和计算方法，特别注意到面波的散射效应对转动分量的影响，并将这一特性引入到转动分量的求取中，使问题的解决更切合于实际，最后选取实际地震记录，利用得到的公式计算出地震面波产生的转动分量。 相似文献
3.
Rotation motion and its effects on strong-motion data, in most cases, are much smaller than that of translational motion and have been ignored in most analyses of strong-motion data. However, recent observations from near-fault and/or extreme large ground motions suggest that these effects might be underestimated and quantitative analyses seem to be necessary for improving our understating of these effects. Rotation motion-related effects include centrifugal acceleration, the effects of gravity and effects of the rotation frame. Detailed analyses of these effects based on the observed data are unavailable in the literature. In this study, we develop a numerical algorithm for estimating the effects of rotational motion on the strong-motion data using a set of six-component ground motions and apply it to a set of rotation rate-strong motion velocity data. The data were recorded during a magnitude 6.9 earthquake. The peak value of the derived acceleration and rotation rate of this dataset are about 186 cm/s/s and 0.0026 rad/s. Numerical analyses of data gives time histories of these rotational motion-related effects. Our results show that all the rotation angles are less than 0.01°. The maximum centrifugal acceleration, effect from gravity and effect of the rotation frame are about 0.03 and 0.14 cm/s/s, respectively. Both these two effects are much smaller than the peak acceleration 186 cm/s/s. This result might have been expected because our data are not near-field and wave motions are expected to be nearly plane waves. However, it is worth noticing that the centrifugal acceleration is underestimated and a small rotational effect can cause large waveform difference in acceleration data. The waveform difference before and after the correction for rotational motion can reach 16 cm/s/s (about 10 %). 相似文献
4.
Methods for estimating rotational components of seismic ground motion and their numerical comparisons* 
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下载免费PDF全文 Rotational components play an important role in natural earthquake research, engineering seismic investigation, building monitoring, seismic exploration and other fields. Traditional researches mainly focus on three translational components, but less on rotational ones. As the precision of rotational sensing techniques has increased, many scholars have paid more attention to the seismic rotational motions. Because the rotational observations are not very popular before and now, approximately converting the translational components into rotational components is utilized in rotation analysis. Based on numerical six-component seismic data with the finite difference method, we compare three different conversion methods, the travelling-wave, frequency-domain and the difference method, to analyze their characteristics and feasibilities when they are applied to estimate rotational components with translational observations. 相似文献
5.
2017年8月8日在四川阿坝州九寨沟县发生了MS 7.0地震，这是继2008年四川汶川MS 8.0地震和四川芦山MS 7.0地震后在此地区发生的又一强震。本研究对此次地震中的66组主震记录进行了常规校正处理，基于此分析了此次地震中典型台站——九寨百合台站的地震动特征，并通过地震动的峰值加速度、反应谱参数分析了近场效应特征。研究结果表明:九寨百合台站的三分量峰值加速度都超过了100 gal，而地震动持时相对较短，并且三分量反应谱在短周期大于Ⅷ度多遇地震设计谱，小于Ⅷ度罕遇地震设计谱；由于九寨沟地震属于典型的走滑型地震，因此地震动参数的方向性特征不明显；九寨沟地震的地震动的峰值加速度以及反应谱谱值小于同等震级的芦山地震，并且小于几个典型衰减关系的预测值。对九寨沟地震的地震动参数特征研究表明，此次地震是一次震级较大、但灾害损毁程度较低的地震。 相似文献
6.
Nguyen Dinh Pham Bor-Shouh Huang Chin-Jen Lin Tuan-Minh Vu Ngoc-Anh Tran 《Journal of Seismology》2012,16(4):709-720
High-frequency rotational motions of P-waves and coda waves were analysed using rotation rate sensors and strong motion array data from the 4 March 2008 TAiwan Integrated GEodynamics Research (TAIGER) explosion experiment in northeastern Taiwan. Theoretical and observational investigations focussed on the effects of this experiment on the free surface. The main goal of this study was to explore possible applications of combined measurements of artificial explosion-derived translational and rotational motions. Also investigated was the consistent ground rotation observed directly by rotation rate sensors and derived using translational seismic arrays. Common near-source high-frequency rotational motion observations and array-recorded translational motions from one shallow borehole explosion are analysed in this study. Using a half-space assumption of plane P-wave propagation across the recording site, we conclude that: (1) rotational motions induced by direct P-waves interacting with a free surface in theory can be used to estimate wave radial direction, velocity and anisotropic properties; (2) rotational motions derived from scattering are predominant among the observed rotations during the TAIGER explosion experiments and allow us to image the heterogeneous structure of the medium at the investigated site; and (3) rotation sensor measurements undertaken during TAIGER explosion experiments may be affected by cross-axis sensitivities, which need to be considered when using the data obtained during these experiments. 相似文献
7.
An effort is made to examine the properties of rotational (torsional and rocking) ground motions using Chiba dense array data. The Chiba array system, located 30 km east of Tokyo, Japan, is composed of 15 boreholes with separation distances varying from 5 to 320 m. This provides a unique opportunity to examine the characteristics of rotational components. For this purpose, 17 events are considered and rotational ground motions are evaluated using spatial derivatives of translational ones. The effects of seismological parameters and separation distances between stations on properties of rotational motions are examined, showing a sudden increase in rotational motions for the earthquakes with large magnitude or PGA and decrease of these motions with increasing separation distance. While the duration of torsional motion is found to be larger than translational ones, there is no significant difference between durations of rocking and vertical motions. The effects of separation distance and earthquake magnitude on rotational response spectra are also investigated. The normalized rotational response spectra are found to be strongly affected by separation distance. The spectral ratios of rotational and translational motions are not linearly proportional to period as suggested by the previous studies. Finally, the torsional motion is predicted from translation ones for different separation distances at the site. The comparison of the predicted and the calculated torsional motions reveals a weak estimation in close separation distances (<30m) and satisfactory predictions in other cases. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
8.
Effect of tilt on strong motion data processing 总被引：5，自引：2，他引：5
In the near-field of an earthquake the effects of the rotational components of ground motion may not be negligible compared to the effects of translational motions. Analyses of the equations of motion of horizontal and vertical pendulums show that horizontal sensors are sensitive not only to translational motion but also to tilts. Ignoring this tilt sensitivity may produce unreliable results, especially in calculations of permanent displacements and long-period calculations. In contrast to horizontal sensors, vertical sensors do not have these limitations, since they are less sensitive to tilts. In general, only six-component systems measuring rotations and accelerations, or three-component systems similar to systems used in inertial navigation assuring purely translational motion of accelerometers can be used to calculate residual displacements. 相似文献
9.
运用震源位错模型, 分析矩形垂直断层及倾斜断层走向滑动和倾向滑动的近场地震动场，以地表地震动的傅立叶振幅谱比为参量考察断层附近地震动空间分布的特点. 结果表明, 断层附近的地震动强度主要受近旁子断层的控制，高强度的地震动分布在紧靠断层两侧有限的带状区域内，长周期分量受断层破裂传播方向性的影响. 走向滑动的方向性影响主要表现在垂直于断层走向的分量，倾向滑动则表现在平行于断层走向的分量，且深震在地面上引起的地震动强度分布比浅震要平缓，影响范围宽. 倾斜断层产生的地震动有明显的上盘效应，空间分布不对称，与观测结果相符. 最后给出了断层附近近场地震动强度分布拟合函数的表达式，并与美国的1997统一建筑规范规定的近场因子作了比较. 相似文献
10.
Mohammad Reza Falamarz-Sheikhabadi Mohsen Ghafory-Ashtiany 《Journal of Seismology》2012,16(4):815-827
The paper addresses the issue of researching into the engineering characteristics of rotational strong ground motion components and rotational effects in structural response. In this regard, at first, the acceleration response spectra of rotational components are estimated in terms of translational ones. Next, new methods in order to consider the effects of rotational components in seismic design codes are presented by determining the effective structural parameters in the rotational loading of structures due only to the earthquake rotational components. Numerical results show that according to the frequency content of rotational components, the contribution of the rocking components to the seismic excitation of short period structures can never be ignored. During strong earthquakes, these rotational motions may lead to the unexpected overturning or local structural damages for the low-rise multi-story buildings located on soft soil. The arrangement of lateral-load resisting system in the plan, period, and aspect ratio of the system can severely change the seismic loading of wide symmetric buildings under the earthquake torsional component. 相似文献
11.
A procedure for the seismic analysis of underground tunnels using recorded free-field earthquakes based on the 2.5D finite/infinite element approach is presented. The near and far fields of the half space are modeled by finite and infinite elements, respectively. Using the 1D wave theory, the nodal force and displacement on the near-field boundary are computed for each spectral frequency of the earthquake. Then, equivalent seismic forces are computed for the near-field boundary for the earthquake spectrum. By assuming the soil-tunnel system to be uniform along the tunnel axis, the 2.5D approach can account for the wave transmission along the tunnel axis, which reduces to the 2D case for infinite transmission velocity. The horizontal and vertical components of the 1999 Chi-Chi Earthquake (TCU068) are adopted as the free-field motions in the numerical analysis. The maximal stresses and distribution patterns of the tunnel section under the P- and SV-waves are thoroughly studied by the 2.5D and 2D approaches, which should prove useful to the design of underground tunnels. 相似文献
12.
13.
David M. Lee 《地震工程与结构动力学》1980,8(4):349-359
This paper examines the effectiveness of a bilinear hysteretic base isolation system in lowering the shear forces and torques generated in a structure by two-way, translatory ground motions. The study is restricted to single-storey, three-dimensional structures having asymmetries in both horizontal directions and being excited by the El Centro (May 1940) earthquake motions. It is shown that with base isolation the structural torques are drastically reduced, even if the structural eccentricity is large. This reduction in structural torque is greatest when the isolation system's centre of stiffness coincides with the structure's centre of mass. The highly dissipative action of the isolation system provides strong modal decoupling which prevents the translational motions from resonantly driving the torsional motions. The maximum base displacements, due to both translation and rotation combined are less than 11 cm, which is well within the limits of currently available isolation system components. The dynamic action of the base isolation system is outlined and currently available isolation system components described. 相似文献
14.
To achieve rational and precise seismic response predictions of large span spatial structures(LSSSs),the inherent non-uniformity and multidimensionality characteristics of earthquake ground motions should be properly taken into consideration.However,due to the limitations of available earthquake stations to record seismic rotational components,the effects of rocking and torsional earthquake components are commonly neglected in the seismic analyses of LSSSs.In this study,a newly developed method to extract the rocking and torsion components at any point along the area of a deployed dense array from the translational earthquake recordings is applied to obtain the rotational seismic inputs for a LSSS.The numerical model of an actual LSSS,the Dalian International Conference Center(DICC),is developed to study the influences of multi-support and multidimensional excitations on the seismic responses of LSSSs.The numerical results reveal that the non-uniformity and multidimensionality of ground motion input can considerably affect the dynamic response of the DICC.The specific degree of influence on the overall and local structural displacements,deformations and forces are comprehensively investigated and discussed. 相似文献
15.
Many strong motion records show that under the strong seismic vibration of, the torsional disfigurement of building structures is a common and serious damage. At present, there are no special sensors for measuring seismic rotation in the world. Most of the experts obtain rotational components through observing deformation, theoretical analysis and calculation. The theory of elastic wave and source dynamics also prove the conclusion that the surface of the earth will rotate when an earthquake occurs. Based on a large number of investigations and experiments, a rotational acceleration sensor was developed for the observation of the rotational component of strong ground motions. This acceleration sensor is a double-pendulum passive servo large-damped seismic rotational acceleration sensor with the moving coil transducer. When an earthquake occurs, the seismic rotational acceleration acts on the bottom plate at the same time. The magnetic circuit system and the middle shaft fixedly connected to the bottom plate follow the bottom plate synchronous vibration, and the moving part composed of the mass ring, the swing frame and the moving ring produces relative corners to the central axis. The two working coils mounted on the two pendulums produce the same relative motion with respect to the magnetic gaps of the two magnetic circuits. Both working coils at this time generate an induced electromotive force by cutting magnetic lines of force in the respective magnetic gaps. The generated electromotive forces are respectively input to respective passive servo large damper dynamic ring transducer circuits and angular acceleration adjusting circuits, and the signals are simultaneously input to the synthesizing circuit after conditioning. Finally, the composite circuit outputs a voltage signal proportional to the seismic rotational acceleration to form a seismic rotational acceleration sensor. The paper presents the basic principles of the rotational acceleration sensor, including its mechanical structure diagram, circuit schematic diagram and mathematical models. The differential equation of motion and its circuit equation are derived to obtain the expressions of the main technical specifications, such as the damping ratio and sensitivity. The calculation shows that when the damping ratio is much larger than 1, the output voltage of the passive servo large damping dynamic coil transducer circuit is proportional to the ground rotation acceleration, and the frequency characteristic of bandpass is wider when the damping ratio is larger. Based on the calibration test, the dynamic range is greater than or equal to 100dB and the linearity error is less than 0.05%. The amplitude-frequency characteristics, the phase-frequency characteristics and their corresponding curves of the passive servo rotational acceleration sensor are acquired through the calculations. Based on the accurate measurement of the micro-vibration of the precision rotating vibration equipment, the desired result is obtained. The measured data are presented in the paper, which verify the correctness of the calculation result. The passive servo large damping rotational acceleration sensor has simple circuit design, convenient operation and high resolution, and can be widely applied to seismic acceleration measurement of earthquake or structure. 相似文献
16.
越来越多的研究表明来自基岩的地震波并不是垂直地面向上传播的。地震波在斜入射与垂直入射时所产生的场地效应有很大不同，由于存在全反射现象，SV波在斜入射时产生的场地效应更为复杂。文章基于均匀弹性半空间地震波传播理论，分别推导得到SV波入射角在小于、大于等于临界角时地震动的计算表达式，通过模型算例研究SV波全反射作用下的地震动特性。研究发现：由SV波产生的地震动主要由入射波和反射波构成，滑行波作用可以忽略；地面运动轨迹具有面波旋转振动特点；随着入射角的增大，地面震动从以水平方向振动为主逐渐过渡到以垂直方向振动为主，两个方向的振动均小于入射波峰值的2倍。 相似文献
17.
Wei Che Qifeng Luo School of Engineering & Technology China University of Geosciences Beijing China 《地震学报(英文版)》2010,(1)
The rotational seismic motions are estimated from one station records of the 1999 Jiji (Chi-Chi), Taiwan, earthquake based on the theory of elastic plane wave propagation. The time-frequency response spectrum (TFRS) of the rota-tional motions is calculated and its characteristics are analyzed, then the TFRS is applied to analyze the damage mechanism of one twelve-storey frame concrete structure. The results show that one of the ground motion components can not reflect the characteristics of the seismic moti... 相似文献
18.
Site response to earthquake loading is one of the fundamental problems in geotechnical earthquake engineering. Most site response analyses assume vertically propagating shear waves in a horizontally layered soil–rock system and simply ignore the effect of site response to vertical earthquake motion, although actual ground motions are comprised of both horizontal and vertical components. In several recent earthquakes very strong vertical ground motions have been recorded, raising great concern over the potential effect of vertical motion on engineering structures. Being a step toward addressing this concern, this paper presents a simple and practical procedure for analysis of site response to both horizontal and vertical earthquake motions. The procedure involves the use of the dynamic stiffness matrix method and equivalent-linear approach, and is built in the modern MATLAB environment to take full advantages of the matrix operations in MATLAB. The input motions can be specified at the soil–bedrock interface or at a rock outcropping. A detailed assessment of the procedure is given, which shows that the procedure is able to produce acceptable predictions of both vertical and horizontal site responses. 相似文献
19.
Power spectral density which describes frequency content is considered one of the most significant properties to be taken into account when generating ground motions through the use of stochastic processes. Using a smoothed and normalized Fourier amplitude spectrum, frequency content for components of motion along a set of principal axes is estimated. Fourier amplitude spectra obtained by this moving-window technique are presented which show the time dependency of frequency content for motions produced by the San Fernando earthquake of 9 February 1971. A mathematical model to simulate ground motion processes is proposed for which both the intensity and frequency content are non-stationary. Using this mathematical model with parameter characteristics along principal axes similar to those of the motions recorded during the San Fernando earthquake, three-dimensional ground motions are synthetically generated. The properties of the simulated motions show general characteristics similar to the characteristics observed in real accelerograms. The suggested model is considered adequate for engineering purposes. 相似文献
20.
The rupture dimensions of earthquake faults are important parameters for characterizing earthquake ruptures and ground motions. Two key parameters to be determined are the rupture depth and dip angle of earthquake faults. Dislocation theory in an elastic half space indicates that if a seismic rupture directly runs up to the ground surface, there exist zero points of horizontal strain in the surface deformation, which correspond to the rupture depths, except for pure strike-slip faults. In this study, we use numerical simulations to investigate the possibility of inferring rupture depths from zero-strain points for cases of buried faults and heterogeneous media. The results show that the correspondence of zero-strain points to the rupture depths can be influenced by the heterogeneity of the underground media and the stress field. For buried faults, the correspondence relationship is approximately valid when the fault depth is <1 km. In addition, the range of earthquake fault dip angles can be estimated by horizontal displacements on the ground. We also study how to determine the rupture depths of faults from InSAR data after large earthquakes, and successfully apply the method to the 2008 Wenchuan earthquake. The method proposed here, which determines the parameters of fault geometry according to surface deformation, is simple and easy to perform. With independent of aftershocks, it can provide valuable constraints to kinematic inversions. 相似文献