Estimation of strong motion distribution in the 1995 Kobe earthquake based on building damage data

The 1995 Kobe earthquake caused unprecedented damage to buildings and civil infrastructures in the city of Kobe and its surrounding areas. In order to evaluate the structural damage in this area due to the earthquake, it is important to estimate the distribution of earthquake ground motion. However, since the number of strong ground motion records is not enough in the heavily damaged areas, it is necessary to estimate the distribution using other data sources. In this paper, the fragility curves for low‐rise residential buildings were constructed using the recorded motions and the building damage data from the intensive field survey by the AIJ and CPIJ group. The fragility curves obtained were then employed to estimate the strong motion distribution in the district level for Kobe and the surrounding areas during the earthquake. The results may be useful to investigate the various damages caused by the earthquake. Copyright © 2001 John Wiley & Sons, Ltd.     

ANALYSIS OF AMPLIFICATION CHARACTERISTICS OF GROUND MOTIONS IN THE HEAVILY DAMAGED BELT ZONE DURING THE 1995 HYOGO-KEN NANBU EARTHQUAKE

To estimate the amplification characteristics of ground motions in the heavily damaged belt zone in Kobe City during the 1995 Hyogo-ken Nanbu earthquake, 3D wave propagation analyses of a 2D deep irregular underground structure model with a vertical discontinuity were performed at an early stage as a preliminary and qualitative study. The hyperelement method was applied to the analyses for incident plane waves expected from the wavefields due to the source mechanism. The observation records at Kobe University of the rock site were used as control motions. The ground motions on the engineering bedrock (assumed to be on the free surface of the Osaka group layers having a shear velocity of 500 m/s) and at ground surface were calculated. The effects of the deep irregular underground structure and shallow surface layers on the ground motion amplification are discussed. Although there are qualifications due to the uncertain characteristics of the input rock motion and shear wave velocities of the underground structure, the analytical results show that the ground motion in the heavily damaged belt zone were amplified due to the focusing effect of the deep irregular underground structure as well as the shallow surface layers, and that the calculated peak ground acceleration (PGA) distribution coincided closely with the distributions of structural damage. © 1997 by John Wiley & Sons, Ltd.     

Nonlinear response of surface soil and NTT building due to soil–structure interaction during the 1995 Hyogo-ken Nanbu (Kobe) earthquake

The 1995 Hyogo-ken Nanbu (Kobe) earthquake brought about enormous damage to structures in the Hanshin and Awaji areas. In this paper the importance of investigating the relationship between ground motion and structural damage is pointed out.

Strong seismic motion was observed at the NTT (Nippon Telegraph and Telephone) Building during this earthquake. The structural damage to this building was relatively slight. In order to evaluate the relationship between ground motion and structural damage, it is necessary to assess the effects of the soil–structure interaction. In this study, the seismic response of the building and of the surface soil were evaluated by means of a nonlinear soil–structure interaction analysis using FEM.

It was found that, the nonlinearity of surface soil near the building had a great effect on the soil–structure interaction, especially the rocking of the building.     

Verification of predicted non-linear site response during the 1995 Hyogo-Ken Nanbu earthquake

The linear and non-linear responses of surface soil layers have been predicted through the simultaneous simulation test against the observed ground motions at the six sites in Kobe City during the 1995 Hyogo-ken Nanbu earthquake. The total stress analysis method and the effective stress analysis method have been applied for the rough and detailed verification of the predicted non-linear dynamic behavior at the PIS and RKI sites including the liquefaction phenomenon. The shear strain distribution along depth, the ratio of excess pore water pressure to initial effective stress, the liquefaction strength parameters to initial effective stress, and the stress–strain curve during the earthquake at the PIS site have been investigated when the predicted ground motion could simulate successfully the observed acceleration time histories and response spectra in the non-linear range.     

Nonlinearity in the response of soils in the 1995 Kobe earthquake in vertical components of records

Strong motion records provided by seismic vertical arrays allow estimation of stress–strain relations in soils at depths from the surface to the location of the deepest device. As an example, time-dependent nonlinear soil behavior was estimated in vertical components of records obtained in the epicentral area of the 1995 Kobe earthquake. Degradation of the rigidity of soils in the strong motion was observed. The constructed nonlinear models of the soil behavior were used for estimating the nonlinear parts in the ground response by the nonlinear system identification technique. Nonlinear parts in the ground response were found to be as high as 50% at 2 km from the fault and 10% at 6–15 km from the fault plane. Odd types of nonlinearity, such as cubic, the fifth, seventh, etc. order, were found to be typical for soils, whereas, nonlinearities of even types are usually weak, but increase in liquefied soils.     

Simultaneous identification of time and space variant dynamic soil properties during the 1995 Hyogoken-Nanbu earthquake

Time and space variant soil properties at a liquefied site were simultaneously identified in the time domain by using borehole array strong motion records. During soil liquefaction at a site, soils usually show a wide variety of non-linear behavior along the depth as well as non-stationary behavior. Strong ground motion records were obtained at Port Island borehole array observatory, Kobe, during the 1995 Hyogoken-Nanbu earthquake. In this study, the instrumented soil was modeled by the equivalent linear MDOF system, and an extended Kalman filter with local iteration was employed for the identification of the soils. The identification process was successfully conducted, and the stress–strain relationships of the soils at the liquefied site were obtained from different depths all at once.     

2022年日本福岛7.4级地震震害分析与对比

2022年3月16日在日本福岛县东部海域发生7.4级地震,本文基于近实时震害评估系统RED-ACT对此次地震进行了快速评估,包括强震动记录分析、区域地震破坏力震害评估结果和典型桥梁破坏,并结合实际震害对比了该系统评估结果以及其他主要震害快速评估系统的分析结果,结果表明：(1)此次地震造成的地面运动强度较大,多数台站记录PGA较2021年福岛7.3级地震更强,反应谱在0.5～1.3s区间呈现远高于2021年福岛地震的趋势。(2)RED-ACT的震害评估结果相较于日本NIED-CRS系统和美国USGS-PAGER系统与实际震害更为接近,在强震动记录较为密集的地区,开展基于强震动时程和建筑非线性分析的震害评估能够得到更为准确的震害评估结果。(3)此次地震对白石市附近桥梁造成了一定的破坏,桥梁破坏附近处的强震动会对典型桥梁结构造成一定程度的破坏。     

Effect of earthquake ground motions on fragility curves of highway bridge piers based on numerical simulation

Fragility curves express the probability of structural damage due to earthquakes as a function of ground motion indices, e.g., PGA, PGV. Based on the actual damage data of highway bridges from the 1995 Hyogoken‐Nanbu (Kobe) earthquake, a set of empirical fragility curves was constructed. However, the type of structure, structural performance (static and dynamic) and variation of input ground motion were not considered to construct the empirical fragility curves. In this study, an analytical approach was adopted to construct fragility curves for highway bridge piers of specific bridges. A typical bridge structure was considered and its piers were designed according to the seismic design codes in Japan. Using the strong motion records from Japan and the United States, non‐linear dynamic response analyses were performed, and the damage indices for the bridge piers were obtained. Using the damage indices and ground motion indices, fragility curves for the bridge piers were constructed assuming a lognormal distribution. The analytical fragility curves were compared with the empirical ones. The proposed approach may be used in constructing the fragility curves for highway bridge structures. Copyright © 2001 John Wiley & Sons, Ltd.     

利用余震频度分布进行宏观震中快速判定

微观震中和宏观震中的偏离是现阶段震后烈度快速判定亟待解决的问题。 本文旨在通过研究中国西部1970年以来7个M_S≥6.5破坏性大地震后24小时内的余震频度N值的空间变化, 分析和判定主震破裂的大致范围, 从中得出可能的宏观震中位置, 为大地震的应急救援提供参考。 本文将主要以2008年汶川地震为例说明最小完整性震级确定的步骤和结果, N值计算方法和N值分布图的绘制以及宏观震中的确定, 最后将7次大地震每个时段估计震中和实际的宏观震中进行比较和分析。 研究结果显示: ① 破坏性大地震24小时内不同时段由余震频度N值分布得到的宏观震中, 可有效缩小由微观震中评估烈度产生的偏差; ② 震后2、 4、 12、 24小时四个时段的估计震中能够作为烈度快速判定的修正因子, 满足震后快速响应的时效性要求。 并且震后24小时的估计震中效果最好。     

汶川特大地震汉源烈度异常原因的初步分析

远离震中的汉源县老县城在汶川大地震中遭到了严重震害,是Ⅵ度区内的唯一的Ⅷ度烈度异常区.汉源的地震烈度异常现象引起学术界的广泛关注.在汉源科学考察基础上,介绍了汉源震害情况,收集和整理了汉源县城及附近有关工程场地的强震和土体力学参数资料.通过背后山滑坡体有限元分析结果与汉源附近强震台记录的比较,从传递函数角度分析了背后山滑坡复活对烈度异常的影响,研究了汉源特殊土层结构对地震动的影响.结果表明,背后山滑坡的复活和特殊土层结构的放大作用等场地条件的影响是引起烈度异常的主要原因.所得结论对进一步分析汉源烈度异常的原因具有一定的参考价值.     

2013年6月2日台湾南投地震强地面运动模拟

2013年6月2日台湾省南投县发生一次里氏6.5级地震,这次地震是最近几年内发生的最大的一次地震,台湾大部分地区以及中国大陆东南沿海城市均有明显震感.为了更深入的理解此次地震的地震波能量传播过程以及强地面运动过程,本文采用三维有限差分方法对此次地震的强地面运动过程进行了模拟.结果显示,台湾中央山脉起伏的地形对此次地震的强地面运动分布特征具有较大的影响,出现了比较明显的地形放大效应;此外,台湾的平原和盆地中的沉积层也对地震波有较强的放大效应.     

青海玛多M7.4地震中桥梁地震破坏现象分析

2021年5月22日青海省玛多县发生了M7.4地震,造成玛多县境内的野马滩1、2号桥破坏,其主要表现为桥梁纵向位移过大导致多跨主梁落梁,桥墩也有不同程度的破损.经现场专家鉴定,地震影响烈度均突破桥梁抗震设计值,并且初步判断这种整齐划一的落梁震害的机理系近断层地震动方向性效应的强速度脉冲作用所致.野马滩大桥位置的地震影响烈度调查结果为Ⅸ,但是野马滩大桥附近无强震动观测台站,大桥附近没有获得地震动记录,这不利于野马滩大桥地震作用下地震响应和破坏机理的研究.另外,野马滩大桥的设计参数和折损情况也很难掌握,桥梁模型难以准确估计.为此,本文拟采用另一座同等抗震设防烈度的桥梁,通过有限元程序,使用反应谱法作为参考,同时使用拟合的地震动和脉冲记录进行桥梁结构反应时程分析,以便间接地揭示玛多地震桥梁地震反应特征和破坏机理.计算结果分析表明,所分析的桥梁结构地震响应位移和内力均超过罕遇地震设计值,其中一条地震动记录最大反应接近极罕遇设计值,导致桥梁结构出现破坏甚至损毁震害现象的出现.     

Estimation of Nonlinear Time-dependent Soil Behavior in Strong Ground Motion Based on Vertical Array Data

To improve our understanding of nonlinear elastic properties of soils, a method is proposed of estimation of stress-strain relations of soils in situ in strong ground motion based on vertical array data. Strong motion records provided by seismic vertical arrays allow estimation of nonlinear stress-strain relations in soil layers at different depths, from the surface down to the location of the deepest device. As an example, records obtained during the main shock of the 1995 Kobe earthquake at Port-Island, SGK, and TKS sites were used to estimate the stress-strain relations in the soil profiles. For different layers, different types of nonlinear stress-strain relations were selected, according to the profiling data. To account for temporal changes in the soil behavior, consecutive parts of records were examined, and for successive time intervals, the relations were found showing the best-fit approximation to the observed data. At Port Island and SGK sites, where the strongest accelerations were recorded, the obtained stress-strain relations showed systematic changes in the upper layers (0–14 m), such as, a progressive reduction of the slopes of the stress-strain curves due to liquefaction at Port Island and reduction and recovery of the slopes at SGK and TKS sites. At the three sites, the stress-strain relations remained stable in layers below 11–14 m. Thus, the proposed approach gives us a representation of the soil behavior in layers at different depths in strong ground motion; it allows calculation of the propagation of arbitrary seismic signals in the studied profiles and estimation of nonlinear components in the ground response by the nonlinear system identification technique. The method can also be applied to evaluate the ground response at sites where profiling data are available and an imposed motion can be estimated.     

Wave energy in surface layers for energy-based damage evaluation

Seismic wave energy in surface layers is calculated based on vertical array records at four sites during the 1995 Hyogo-ken Nambu earthquake by assuming vertical propagation of SH waves. The upward energy generally tends to decrease as it goes up from the base layer to the ground surface particularly in soft soil sites. Theoretical study on 1D multi-layers model to investigate the basic energy flow mechanism indicates that the energy at the ground surface can be smaller on softer soils due to high soil damping during strong shaking even if resonance effect is considered. A simple calculation for a shear-vibrating structure resting on foundation ground shows that induced strain in the structure is directly related to the energy or the energy flux of surface layers. Hence, a general perception that soft soil sites tend to suffer heavier damage than stiff sites should be explained not by greater incident energy but by other reasons such as degree of resonance. Furthermore, it is recommended that not only acceleration or velocity but also S-wave velocity should be specified at a layer where a design seismic motion is given, so that the seismic wave energy can clearly be quantified in seismic design practice.     

Ground motion characteristics of the Chi‐Chi earthquake of 21 September 1999

The purpose of this paper is to investigate the ground motion characteristics of the Chi‐Chi earthquake (21 September 1999) as well as the interpretation of structural damage due to this earthquake. Over 300 strong motion records were collected from the strong motion network of Taiwan for this earthquake. A lot of near‐field ground motion data were collected. They provide valuable information on the study of ground motion characteristics of pulse‐like near‐field ground motions as well as fault displacement. This study includes: attenuation of ground motion both in PGA and spectral amplitude, principal direction, elastic and inelastic response analysis of a SDOF system subjected to near‐field ground motion collected from this event. The distribution of spectral acceleration and spectral velocity along the Chelungpu fault is discussed. Based on the mode decomposition method the intrinsic mode function of ground acceleration of this earthquake is examined. A long‐period wave with large amplitude was observed in most of the near‐source ground acceleration. The seismic demand from the recorded near‐field ground motion is also investigated with an evaluation of seismic design criteria of Taiwan Building Code. Copyright © 2000 John Wiley & Sons, Ltd.     

Simulation of accelerograms from simplified deterministic approach for the 23rd October 2004 Niigata-ken Chuetsu,Japan earthquake

A simple hybrid approach for the simulation of strong ground motion is presented in this paper. This approach is based on the deterministic modelling of rupture plane initially started by Midorikawa, Tectonophysics 218:287–295, (1993) and further modified by Joshi, Pure Appl Geophys (PAGEOPH) 8:161, (2004). In this technique, the finite rupture plane of the target event is divided into several subfaults, which satisfy scaling relationship. In this paper, simulation of strong ground motion due to a rupture buried in a earth medium consisting of several layers of different velocities and thicknesses is made by considering (1) transmission of energy at each layer; (2) frequency filtering properties of medium and earthquake source; (3) correction factor for slip of large and small magnitude earthquakes and (4) site amplification ratio at various stations. To test the efficacy of the developed technique, strong motion records were simulated at different stations that have recorded the 2004 Niigata-ken Chuetsu, Japan earthquake (M _s 7.0). Comparison is made between the simulated and observed velocity and acceleration records and their response spectra. Distribution of peak ground acceleration, velocity and displacement surrounding the rupture plane is prepared from simulated and observed records and are compared with each other. The comparison of synthetic with the observed records over wide range of frequencies shows that the present technique is effective to predict various strong motion parameters from simple deterministic model which is based on simple regression relations and modelling parameters.     

Ultrasonic modelling research of earthquake response of underground lifeline engineering

Earthquake response of underground lifeline engineering is investigated by the method of ultrasonic model experiments in this paper. From general field conditions, two models of underground lifeline engineering, one for non-uniform field and the other for uniform field, are designed based on the similarity principle. Besides analysis of seismic phases, a series of analyses especially on particle vibration are carried out. The results show that: The shorter the epicentral distance, the greater are the intensity variation and the change rate of intensity variation of earthquake ground motion, so the more disadvantageous to underground pipelines. In soft covering layer, compressional waves mainly cause radial flexures deformation, but shear wave result in axial dilation deformation of the pipelines; when the thickness of the covering layer is smaller (less than seismic wave length), the rhythmic variation of the intensity of earthquake ground motion is controlled mainly by the wave length of seismic waves in the bedrock. The property of the covering layer has considerable effect on earthquake ground motion. For different covering layers, their effect on each component of earthquake ground motion is not the same. Owing to the effect of wave propagation, the ground is in different states of particle vibration at different times, and there is considerable difference in phase and intensity of particle vibration between two different covering layers near their junction line or surface. Because underground lifelines tend to vibrate with the particles of the earth around it, this results in different deformation of underground pipelines under different conditions. So, it is necessary to take corresponding anti-seismic countermeasures for pipelines according to their practical situations. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 104–110, 1992. This paper is part of the research supported by Funds of Doctoral Faculty of National Education Committee.     

基于机器学习的地震动特征提取与模拟以2021年云南漾濞6.4级地震为例

随着地震动数据数量的增长和质量的提高,将基于数据驱动的机器学习方法应用到地震动模拟中有重要意义。以2021年5月21日云南漾濞M_S6.4地震为例,利用主成分析方法从前震及余震地震动记录中提取特征母波时程,将地震动三要素作为模拟误差约束,在求解母波的线性组合系数时使用多目标优化算法寻优,最终找到帕累托最优解作为模拟目标台站记录时的组合系数,得到模拟地震动时程。结果表明:主成分析法在对实际地震动记录进行特征提取后,得到的特征母波时程可以在一定程度上保留原始数据的主要信息;考虑幅值、频谱和持时这三要素的角度去控制模拟误差,可以使得模拟的地震动时程更加接近真实记录。提出的基于特征提取的地震动模拟方法可以为基于小震数据合成大震地震动提供参考。     

A new approach for estimating seismic damage of buried water supply pipelines

Conventional damage prediction methods for lifeline structures are primarily based on peak ground motion measurements. However, line structures such as lifelines suffer damage that is mainly induced by the strain of the ground and therefore are likely to be vulnerable to sharp spatial changes in the ground motion. In this study, we propose a measure for evaluating the damage incurred by underground water supply pipelines based on the spatial gradient of the peak ground velocity (PGV), in an attempt to quantify the effects of the geospatial variabilities in the ground motion on pipeline damage. We investigated the spatial distribution of the damage caused to water pipelines during the Niigata‐ken Chuetsu earthquake on October 10, 2004 (Japan Meteorological Agency magnitude (M_JMA) of 6.8) and the Kobe earthquake on January 17, 1995 (M_JMA7.3) and compared the surveyed damage with the PGV distribution as well as with the gradients of the PGV calculated around the damage areas. For the Kobe earthquake, we used the PGV distribution obtained by the strong‐motion simulation performed by Matsushima and Kawase 1 . In case of the Chuetsu earthquake, we estimated the ground motion using a broadband‐frequency‐based strong‐ground‐motion simulation method based on a multiasperity source model. In both cases, we calculated the gradients of the PGV along the geographical coordinates, with the amplitude of the PGV gradient vector being employed as the damage estimator. Our results show that the distribution of damage to underground water supply pipelines exhibits a greater correlation with the gradients of the PGV than with the PGV itself. Thus, the gradient of the PGV is a useful index for preparing initial‐screening hazard maps of underground facilities. Copyright © 2017 John Wiley & Sons, Ltd.     

Simulation of strong earthquake characteristics of a scenario earthquake (MS7.5) based on the enlightenment of 2022 MS6.9 earthquake in Menyuan

The Menyuan area is an important transportation hub in the Hexi Corridor. The Menyuan M_S6.9 earthquake that occurred on January 8, 2022 had a major impact on the local infrastructure and transportation of this region. Due to the high possibility of similar strong earthquakes occurring in this area in the future, preliminary assessment of the seismic intensity characteristics of destructive earthquakes in this region is essential for effective disaster control. This paper uses the empirical Green′s function (EGF) method as a numerical simulation tool to predict the ground motion intensity of Datong Autonomous County under the action of the scenario earthquake (M_S7.5). Seismic records of aftershocks of the 2016 Menyuan M_S6.4 earthquake were used as Green’s functions for this simulation. The uncertainties associated with various source parameters were considered, and 36 possible earthquake scenarios were simulated to obtain 72 sets of horizontal ground motions in Datong County. The obtained peak ground acceleration (PGA) vs. time histories of the horizontal ground motion were screened using the attenuation relationships provided by the fifth-edition of China's Seismic Ground Motion Parameter Zoning Map and the NGA-West2 dataset. Ultimately, 32 possible acceleration-time histories were selected for further analysis. The screened PGA values ranged from 78.8 to 153 cm/s². The uncertainty associated with the initial rupture point was found to greatly affect the results of the earthquake simulation. The average acceleration spectrum of the selected acceleration-time history exceeded the expected spectrum of a intermediate earthquake, which means that buildings in Datong County might sustain some damage should the scenario earthquake occur. This research can provide reliable ground motion input for urban earthquake damage simulation and seismic design in Datong County. Growing the dataset of small earthquakes recorded in this region will facilitate the large-scale simulation of ground motions under different earthquake scenarios.