The response of stromatolites to seismic shocks： Tomboliths from the Palaeoproterozoic Chaibasa Formation, E India

It is demonstrated here for the first time how Palaeoproterozoic stromatolites survived seismic disturbance of their substrate. The stromatolites under study could have been cyanobacteria or any other photo-autotrophic microbes, which formed mats that covered a substrate of very fine-grained sandstones and mudstones of the Chaibasa Fm. in eastern India. The sediments represent a shelf environment. The local abundance of the stromatotites suggests that the tow-energy environment formed a suitable habitat. The common phases of tectonic quiescence were, however, occasionally interrupted by seismic shocks. These were sufficiently strong to deform the mat layers, the tower parts of which might already have been （semi-） consolidated. The mats became partly folded, partly faulted, and already consolidated parts of the stromatotite layers broke off. This can be deduced from the angular shapes of part of the broken-off fragments. It appears, however, that part of these fragments were stilt sufficiently soft to become rounded and deformed by rotting over the seafloor, probably under the influence of tidal currents. When come to rest, these fragments served as a new substrate for new generations of the microorganisms. These micro-organisms thus survived by continued growth on the reworked fragments and built up new stromatolites that may show an ‘angular disconformity＇ with the stromatotites of their substrate. It thus is shown that stromatotites have an adequate response to a sudden disturbance of their habitat, and that they survive earthquakes by colonization of broken-off fragments. We call the ‘healed＇ fragments ‘tombotiths＇ （tumbled stones）.

The response of stromatolites to seismic shocks: Tomboliths from the Palaeoproterozoic Chaibasa Formation,E India: Discussion and liquefaction basics

This discussion of a paper by Van Loon et al.（2016）, published in the Journal of Palaeogeography（2016, 5（4）, 381e390）, is aimed at illustrating that there are fundamental deficiencies, which include（1）incomplete etymological reasoning for proposing a new genetic term ＂tomboliths＂ for stromatolitic bioclasts in the Palaeoproterozoic Chaibasa Formation, eastern India,（2） omission of empirical data in documenting depositional facies using sedimentological logs,（3） misapplication of the stratigraphic concept of ＂angular unconformity＂,（4） failure to consider the multifarious origins of earthquakes, and（5） a dated view on the basic tenets of process sedimentology and triggering mechanisms of liquefaction that are the basis for forming soft-sediment deformation structures（SSDS）. As a consequence, their conclusions are unconvincing.

“The response of stromatolites to seismic shocks: Tomboliths from the Palaeoproterozoic Chaibasa Formation,E India”: Reply

Our contribution about a newly recognized sedimentological feature, which we called tombolith,has raised some comments on the etymology of the term, the assumed lack of field data, the usage of a term that has a special meaning in stratigraphy, the origin of the seismic shocks that played a role, so-called basic tenets, the origin of soft-sediment deformation structures, and the role of liquefaction. We argue that most comments result from an insufficiently thorough reading of our text, whereas some other remarks concern aspects that we did not deal with. Finally, several remarks are based on outdated literature and from insufficient knowledge of the regional geology.

大跨度钢箱系杆拱桥减隔震措施对比研究

以某跨河大跨度钢箱系杆拱桥为研究对象,研究不同措施下桥梁的减隔震性能。通过“m”法,利用桥梁有限元软件Midas Civil进行动力分析;通过人工合成地震波,采用FDB模型、粘滞阻尼器MAXWELL模型进行模拟,对大跨度钢箱系杆拱桥进行非线性时程分析,对比分析摩擦摆支座、速度锁定器、拉索减震支座的减震效果。研究结果表明:三种减隔震措施下,墩柱所受的轴力差异较小,摩擦摆支座及拉索减震支座所受的剪力、弯矩差异较小,速度锁定器作用下,墩柱所受的剪力及弯矩差异较大。通过对比分析,选用摩擦摆支座能较好地满足工程需求,减震效果良好。

自复位变摩擦阻尼器增强榫卯节点抗震性能研究

研究橡胶碟簧自复位变摩擦阻尼器榫卯节点抗震性能,参照西南地区传统木结构典型做法,制作直榫和台阶透榫节点进行低周反复加载试验,设计增强和未加固试件,对比榫卯节点破坏形态、滞回曲线和骨架曲线。研究结果表明,增设SFD试件拔榫量得以有效降低,榫头断裂、劈裂现象得到显著改善;不同节点滞回曲线均呈Z字形,未加固节点滑移现象更为突出;经SFD加固后的节点滞回曲线更加饱满,耗能能力、承载力和刚度均有显著提升。

钢混组合梁减隔震抗震优化设计分析

为确保钢混组合梁抗震设计性能最优,依托黄江跨航道主跨为138 m的大跨度槽型钢混组合连续梁桥,针对减隔震支座多参数进行优化研究,选择支座尺寸、铅芯直径以及硬化率作为分析参数,分别选取墩底纵向弯矩和横向弯矩两个指标作为目标函数,定义结构综合目标函数W。基于正交试验方法的参数分析,确定钢混组合梁桥抗震性能最优参数组合。采用极差分析法对W进行分析,获得结构设计参数对抗震性能的敏感性及显著性。结果表明,钢混组合梁桥抗震性能最优减隔震支座参数为:减隔震支座尺寸为1 300 mm×1 300 mm,铅芯直径为190 mm,硬化率为0.20,较原设计方案纵向墩底弯矩减小了41.9%,横向墩底弯矩减小了30.5%;参数敏感性程度由强到弱依次为支座尺寸、硬化率、铅芯直径。

近断层主余震考虑斜入射下的重力坝响应分析

一次大的地震中一般存在主震和余震,当震源距离地面较近时,近断层主余震序列通常以某一角度斜入射至地基,因此只考虑地震波垂直入射的情况是不适合的,有必要考虑地震波在多个角度下斜入射的情况。选取3条近断层实测主余震序列,推导地震动P波斜入射界面等效节点力公式,并验证其可行性;以Koyna大坝为研究对象,研究了单个主震和主余震序列2种工况下入射角在0°~90°之间时的大坝地震响应,以位移、损伤指数、损伤耗散能3个指标对震后坝体破坏进行了分析,建立了局部损伤指数量化分析损伤程度。研究表明:近断层单个主震和主余震2种工况入射角在15°~75°之间时,大坝地震响应均大于垂直入射情况;在多种性能指标下,主余震序列下的地震响应均大于单个主震。

高层隔震结构减震机理和设计分析

随着《建筑抗震管理条例》的颁布,隔震建筑在工程建设中的应用将越来越广泛。以福州某办公楼隔震结构设计为研究对象,采用有限元软件YJK和ETABS分析了主要振型的反应谱。给出了抗震设计目标确定的方法、地震波的选取方法和减震机理,得出了可供工程技术人员借鉴的主要结论:地震波选取时可通过观察地震波的时程曲线图的主要周期点和最大加速度值并对比反应谱与规范谱的拟合度,来判断其与建筑场地是否相适应;高层结构在底部设置隔震支座能够显著改善上部结构的地震反应谱,其减震机理并不是延迟周期而是滤波原理。

RC框架消能减震结构的地震易损性分析

消能减震结构在减震后需要进行减震结构损伤水平的评估以及结构可靠度和地震易损性的研究。文章以钢筋混凝土框架结构为研究对象,以黏滞阻尼器为消能减震装置,采用有限元分析软件ETABS建立消能减震模型并进行传统的小震作用下的弹性时程分析和基于增量动力分析的地震易损性分析,参考结构在不同强度的地震动作用下到达各极限状态的量化指标得到其对应的地震易损性概率,由此确定结构在不同地震动作用下处于各个不同性能水准下的失效概率。结果表明:在设置黏滞阻尼器之后,结构的抗震性能得到有效提升,可以满足“小震不坏,中震可修,大震不倒”的性能指标;同时,基于增量动力分析的地震易损性分析也可以为实际工程的减震设计、灾害评估和未来的地震损失预测提供简明有力的参考依据。

建筑结构设计中的隔震减震措施

在地震频繁的地区,建筑结构的抗震能力至关重要。传统的刚性结构在地震中容易受到严重破坏,造成巨大的经济损失和人员伤亡。为了提高建筑物的抗震性能,隔震减震技术应运而生。隔震减震技术通过引入隔震层或减震装置,在地震中分离结构与地基,减小结构的振动响应,保护建筑及其内部系统。因此,隔震减震技术在当前的建筑结构设计中扮演着重要的角色。基于此,本篇文章对建筑结构设计中的隔震减震措施进行研究,以供参考。

可控冲击波震源技术在陕北沙漠区地震勘探的应用

针对现有地震勘探震源存在问题和局限性,创新性地将金属丝电爆炸可控冲击波技术应用于地震勘探中,分析了金属丝电爆炸可控冲击波技术和产生原理。在掌握金属丝电爆炸可控冲击波技术作为地震勘探震源技术的特点和陕北沙漠地区进行现场激发试验的情况下,从理论分析和现场试验验证了金属丝电爆炸可控冲击波技术作为震源技术的可行性。通过对获取的数据进行定量分析,认为可控冲击波技术可作为一种新型震源技术,且在陕北沙漠区煤田地震勘探领域具备较好的应用发展前景。同时,通过总结试验中存在的问题,为下一步的改进提供方向。

大跨度悬索桥抗震设计与加固方法

悬索桥是一种介于梁桥和拱桥之间的桥梁形式,在跨越山谷、江河、海湾等地形条件时具有明显优势。悬索桥的抗震设计是对悬索桥在地震作用下的结构响应进行分析,提出了以增加关键构件、结构形式和调整阻尼比3种方法为主的抗震设计方案。基于地震反应分析结果,对悬索桥抗震性能进行评估,提出悬索桥减震、隔震的有效措施以及结构防震和抗震的加固方法。

Seismic Tremors and Their Relation to Cryosphere Dynamics in April 2015 around the Lützow-Holm Bay, East Antarctica

Characteristics and statistics of seismic tremors occurring during April 2015 were investigated by using short-period and broadband seismographs deployed at Syowa Station (SYO), in the Lützow-Holm Bay (LHB), East Antarctica. In order to examine a relationship between surface environments in particular cryosphere variation, the MODIS satellite images were utilized for comparison with the detected tremor events. Since a large volume of sea-ice was discharged during the April, together with several large icebergs passed through from the west to the east at northern edge of the fast sea-ice of LHB, it was expected to detect seismic tremors involving cryospehre dynamics. During the month, a total number of 49 tremor events including short duration ice shocks were identified. Majority of the events (N = 39) had their duration times more than 15 minutes, which were divided into both tremors and ice shocks on the basis of experienced definition at SYO. Cryospheric sources recorded by seismic tremors were classified into several origins (collision, calving, crevassing, crashing, etc.): “crevassing events” along the large cracks inside the fast sea-ice in LHB (04 April), “discharge events” of fast sea-ice from the Bay (07 April), “collision events” between iceberg and the edge of fast sea-ice (14 April), “crashing movement” between fragmentation of fast sea-ice and packed sea-ice (18 April), and other origins. In particular, strong amplitude tremors with harmonic overtones were assumed to be occurred independently from whether condition, because these overtone tremors were identified at less stormy days by comparison with infrasound data at SYO.

On some problems of seismic crustal phase

In this paper, some practical problems in seismological observations are discussed on the identification of seismiccrustal phase, such as: “whether P (Pg) and S(Sg) are direct waves or not?”; “whether S(Sg) and Lg as well asng and P (Pg) are two kinds of waves or identical wave?”;“on seismoiogicai phases in regional travel-timetable”;“on the symbols and identifications of phases in seismological observation repors”;“on the relation between mLg and ML”, and so on. Some confused ideas on these problems are clarified.

Post-seismic relaxation from geodetic and seismic data

We have examined the aftershock sequence and the post-seismic deformation process of the Parkfield earthquake （2004, M = 6, California, USA） source area using GPS data. This event was chosen because of the possibility of joint analysis of data from the rather dense local GPS network （from SOPAC Internet archive） and of the availability of the rather detailed aftershock sequence data （http：]/www.ncedc.org[ ncedc[catalog-search.html）. The relaxation process of post-seismic deformation prolongs about the same 400 days as the seismic aftershock process does. Thus, the aftershock process and the relaxation process in deformation could be the different sides of the same process. It should be noted that the ratio of the released seismic energy and of the GPS obtained deformation is quite different for the main shock and for the aftershock stage. The ratio of the released seismic energy to the deformation value decreases essentially for the post-shock process. The similar change in the seismic energy[deformation value ratio is valid in a few other strong earthquakes. Thus, this decrease seems typical of aftershock sequences testifying for decrease of ratio of elastic to inelastic deformation in the process of post-shock relaxation when the source area appears to be mostly fractured after the main shock occurs, but the healing process had no yet sufficient time to develop.

Study of the correlations between main shocks and aftershocks and aftershock synthesis method

To consider the infl uence of aftershocks in engineering design, the correlations between main shocks and aftershocks should be examined, and an aftershock simulation method with main shock ground motions needs to be developed. In this study, the data on the sequences of main shock–aftershock ground motions and other related parameters were collected. Using these data, correlations between the magnitude, frequency, duration and energy of the main shock–aftershock ground motions were investigated. The results showed that the magnitude of the aftershock can be larger than that of the main shock. The shapes of the Fourier amplitude spectra of main shocks and aftershocks were similar;however, the predominant frequency and high-frequency components of the aftershock tended to be larger. Considering the magnitude diff erence between the main shock and the aftershock, the correlation of durations was explored. Additionally, a new concept, the duration ratio, was defi ned to describe the concentration of seismic energy release, and main shock energy was strongly positively correlated with the energy attenuated during the main shock–aftershock sequence. Finally, based on these results regarding correlation, an aftershock synthesis using recorded main shock ground motions was constructed with the trigonometric series method for seismic design, and some examples are given to analyze the rationality of this synthetic method.

新型装配式剪力墙抗震性能试验

针对强震作用下典型装配式剪力墙结构的破坏机理和薄弱环节,提出一种具有耗能减震功能的新型装配式剪力墙。采用模型试验和数值模拟相结合的方法,设计制作了4片缩尺比1∶1.54、剪跨比1.52的新型装配式剪力墙试件,并对其进行了相应的抗震性能试验,系统分析了螺栓数量、轴压比和边缘构件纵筋配筋率对试件破坏模式、滞回性能、承载能力、变形性能、刚度退化及耗能能力的影响规律。试验结果表明:各试件破坏模式与相同剪跨比的现浇剪力墙基本一致,呈弯剪型破坏;但新型装配式剪力墙具有更为优异的滞回性能和耗能能力,其在破坏点的耗能值显著高于普通现浇墙体;当螺栓数量减少时,新型装配式剪力墙承载能力无明显变化,但滞回性能降低、墙体变形加剧;轴压比或边缘构件纵筋配筋率的降低会导致剪力墙承载能力降低和极限位移增大。最后采用ABAQUS软件建立了相应试件的有限元模型,模拟结果与试验结果吻合较好,表明所建模型的正确性,能够将其应用于新型装配式剪力墙的分析之中。

Signal characteristics of coal and rock dynamics with micro-seismic monitoring technique

In this study,differences of signal characteristics between mine shocks and coal and gas outbursts in coal mines were examined with the micro-seismic monitoring technique and time–frequency analysis.The duration of the mine shock is short while the coal and gas outburst lasts longer.The outburst consists of three stages:the pre-shock,secondary shock and main shock stage,respectively.The velocity amplitude of the mine shock is between 10^(-)5and 10^(-3)m/s,which is higher than that of the outburst with the same energy level.In addition,in both cases,the correlation between the velocity amplitude and energy is positive while the correlation between the signal frequency band distribution and energy is negative.The signal frequency band of the high energy mine shock is distributed between 0 and 50 Hz,and the low energy mine shock is between 50 and 100 Hz.The fractal characteristics of mine shocks were studied based on a fractal theory.The box dimensions of high energy mine shocks are lower than the low energy ones,however,the box dimensions of outbursts are higher than that of mine shocks with the same energy level.The higher box dimensions indicate more dangerous dynamic events.

组合消能减震技术在工程项目中的应用与研究

随着消能减震技术发展日趋成熟,基于结构性能需求的各种消能器产品应运而生。目前建筑市场应用较广泛的消能器主要包括位移型和速度型两种。根据项目应用实际情况,大部分减震项目使用的消能器类型单一,未能结合不同结构体系的特点、需求及限制进行消能减震机理及效率研究,且经济性一般。在设计日趋精细化形势下,提出基于结构性能需求的组合消能减震技术,即针对不同结构体系、不同楼层等根据性能需求“量身定制”相应类型的消能器,以最大程度发挥不同类型消能器减震效率及共同作用的一种组合减震技术。两个不同工程实例的研究结果表明:相比传统单一消能器方案,组合消能减震技术可根据结构特点及性能需求,为不同阶段及设计水准下的结构提供附加刚度及附加阻尼,“量身定制”消能器减震机理明确且减震效率、经济性均较好。

考虑地震滑冲效应的高铁简支梁桥横向减震体系研究

对近断层地震滑冲效应作用下高铁简支梁桥横向碰撞响应及其减震体系进行了研究。以一座5跨32 m简支梁桥为背景,采用Abaqus软件建立全桥有限元模型。分析了远场地震和近断层地震滑冲效应作用下桥梁横向地震响应的差异,探究了传统抗震挡块的适用性;对比分析了“挡块+拉索”组合、全桥单独安装拉索限位器及单独安装减震榫等3种减震体系的减震效果。结果表明:与远场地震相比,近断层地震滑冲效应作用下传统抗震挡块完全失效,落梁风险显著增加;挡块与垫石间隙越小,“挡块+拉索”的减震效果越好;拉索限位器的减震效果随拉索自由程减小而提高;减震榫取最优刚度时,能够显著减小桥梁地震响应;综合比选,全桥单独安装减震榫的减震体系最佳。