The inclusion record of fluid evolution,crack healing and trapping from a heterogeneous system during rapid cooling of pegmatitic veins (Dronning Maud Land; Antarctica)

Granitoid (pegmatite and aplite) veins in metamorphic rocks and intrusive syenites of central Dronning Maud Land, Antarctica, are flanked by conspicuous light‐coloured alteration halos, which represent the damage zone of fracture propagation. The damage zone is characterized by a high density of sealed or healed microcracks, about 1 order of magnitude above background. Fluid inclusions along healed microcracks in quartz of both pegmatite and alteration halos are inspected by optical and scanning electron microscopy, and their composition is analysed by microthermometry and quadrupole mass spectrometry. The similar inclusion record in the granitoid vein and in the damaged host rock indicates the derivation of the fluids from the hydrous melt phase. The aqueous inclusions bear abundant daughter crystals, mainly silicates, and may represent a hydrous melt. The volatile composition is variable in the system H₂O–CO₂, with mostly subordinate amounts of N₂. Phase separation with partitioning of CO₂ into the fluid phase coexisting with the hydrous melt, and possibly immiscibility in the subsolidus range, govern fluid evolution during cooling. The variable CO₂/N₂ ratio suggests mixing with fluids from an external source in the host rock and vigorous circulation at an early stage of high transient permeability. Experiments have shown that healing of microcracks at high temperatures is a matter of hours to weeks, hence similar in time scale to the cooling of the cm‐ to dm‐thick granitoid veins. In this case, rapid cooling and concomitant crack healing in a system undergoing phase separation causes a broad compositional variability of the inclusions due to necking down, and the underpressure developing in closed compartments precludes a meaningful thermobarometric interpretation.     

2015尼泊尔地震后加德满都谷地世界文化遗产破坏特征

2015尼泊尔地震对加德满都谷地的世界文化遗产造成不可估量的损失。为了探究谷地文化遗产震害整体分布特征,对谷地世界文化遗产建筑的震害状况开展实地调查,划分了三类文化遗产震害等级标准,形成了六处世界文化遗产的震害图并对其进行统计分析,加德满都、帕坦和巴德岗三处杜巴广场震后保存基本完好的文化遗产建筑占各自总数的39.5%、53.3%、50%,斯瓦扬布纳特寺、昌谷纳拉扬寺和博达哈大佛塔主体保存基本完好,附属建筑不同程度地破坏。加德满都、帕坦和巴德岗三处杜巴广场地层的松软沉积层放大地震效应使建筑严重破坏,斯瓦扬布纳特寺、昌谷纳拉扬寺震害主要受地形特征影响。考察成果为我国同类遗产建筑的抗震防护提供参考。     

白居塔塔体结构稳定性分析研究

在对白居塔建筑形制调查研究基础上,区分塔体内嵌高山体和内嵌低山体两种情况,确定重力作用以及重力和地震耦合作用两种工况。基于采用岩土摩尔—库伦本构模型的有限元分析技术,对白居塔和山体的耦合结构进行稳定性分析。得出以下结论:自重作用下,整体结构稳定性满足,且有较高的安全稳定系数;白居塔整体结构的刚度较大,整个结构体系属于抗震有利体系;白居寺整体结构基频模态以侧倾为主;在7°(基本加速度0.15 g)多遇地震作用下,两个模型整体结构的抗震稳定性较好,结构不会产生整体性失稳破坏;在8°(基本加速度0.3 g)多遇地震作用下,较高山体模型主体结构基本处于安全状态,较低山体模型主体结构不满足稳定要求;较高山体的模型相对于较低山体的模型,安全稳定性要高。     

Linked (im)mobilities and the relational politics of movement in post-earthquake Nepal

ABSTRACT

This article highlights the importance of various (im)mobilities that were induced by the massive 7.8-magnitude earthquake that struck Nepal on 25 April 2015. It analyzes over 120 news articles published in the immediate aftermath of the earthquake, arranging these into a mobility-centric narrative that highlights the politics of movement in the disaster’s wake. Drawing on the theoretical and methodological “mobilities turn”, I introduce the concept of linked (im)mobilities to demonstrate the complex dialectics structuring (im)mobilities after the disaster. More specifically, Nepal’s post-earthquake (im)mobilities intersected with one another and with a variety of geographic and political factors to produce a mutually constitutive web of contingent movements. Attending to these not only underscores the centrality of (im)mobilities themselves. By raising questions of scale, inequality, bordering, and “islanding”, the approach advanced here widens our analytical frame. It offers a conceptual architecture capable of encompassing more factors (beyond mobility), thereby facilitating a broader understanding of the disaster event and its various outcomes.     

Carbon dioxide controlled earthquake distribution pattern in the NW Bohemian swarm earthquake region,western Eger Rift,Czech Republic – gas migration in the crystalline basement

The ascent of magmatic carbon dioxide in the western Eger (Oh?e) Rift is interlinked with the fault systems of the Variscian basement. In the Cheb Basin, the minimum CO₂ flux is about 160 m³ h^?1, with a diminishing trend towards the north and ceasing in the main epicentral area of the Northwest Bohemian swarm earthquakes. The ascending CO₂ forms Ca‐Mg‐HCO₃ type waters by leaching of cations from the fault planes and creates clay minerals, such as kaolinite, as alteration products on affected fault planes. These mineral reactions result in fault weakness and in hydraulically interconnected fault network. This leads to a decrease in the friction coefficient of the Coulomb failure stress (CFS) and to fault creep as stress build‐up cannot occur in the weak segments. At the transition zone in the north of the Cheb Basin, between areas of weak, fluid conductive faults and areas of locked faults with frictional strength, fluid pressure can increase resulting in stress build‐up. This can trigger strike‐slip swarm earthquakes. Fault creep or movements in weak segments may support a stress build‐up in the transition area by transmitting fluid pressure pulses. Additionally to fluid‐driven triggering models, it is important to consider that fluids ascending along faults are CO₂‐supersaturated thus intensifying the effect of fluid flow. The enforced flow of CO₂‐supersaturated fluids in the transitional zone from high to low permeability segments through narrowings triggers gas exsolution and may generate pressure fluctuations. Phase separation starts according to the phase behaviour of CO₂‐H₂O systems in the seismically active depths of NW Bohemia and may explain the vertical distribution of the seismicity. Changes in the size of the fluid transport channels in the fault systems caused, or superimposed, by fault movements, can produce fluid pressure increases or pulses, which are the precondition for triggering fluid‐induced swarm earthquakes.     

甲基三甲氧基硅烷对砂岩石刻封护性能的实验室研究

为了解砂岩石刻用甲基三甲氧基硅烷材料封护处理后的各项性能,选择四川省内风化较严重的摩崖造像区的砂岩作为实验样品,采用浸水、酸雾、盐老化、光老化、循环破坏等方法对材料的憎水性、透气性、耐老化性能进行实验测试。试验表明,砂岩样品用甲基三甲氧基硅烷封护处理后其憎水性、耐老化性都有较大的提高,透气性没有太大的改变,半涂样品经循环破坏处理后,表面出现开裂现象。通过研究表明,甲基三甲氧基硅烷材料处理砂岩后其憎水性和耐老化性都较好,但循环破坏实验提示,甲基三甲氧基硅烷材料处理石刻可能对其表面产生负作用,在石刻保护中应慎重使用。     

Performance and Risks of Salt-Accumulating Renders in Relation to Their Moisture Transport Properties

Salt-accumulating renders are usually applied in several layers with different specific properties of moisture transport. An extensive experimental programme was carried out to establish a relationship between those properties of individual layers and the performance of combined systems on a salt-laden substrate. Each of the 20 renders was characterized separately in absorption and drying tests, vacuum saturation tests, dry cup tests, mercury intrusion porosimetry, and ultrasound wave velocity measurements. Each of the 12 combined render systems was applied on a brick, which was then saturated with a concentrated NaCl solution by free capillary uptake. Subsequently the assembly was closed at the bottom and subjected to an accelerated drying test (50° C and 15% relative humidity). Moisture and salt profiles over the depth were taken regularly during 1 month. The results reveal very different degrees of effectiveness and levels of risk for the substrate, which are related to the moisture transport properties.     

汶川地震导致的古建筑震害

为了解汶川地震造成的古建筑震害及对古建筑的保护,根据古建筑震害资料,通过归纳方法,获得了古建筑不同的震害症状：对木结构而言,主要有地基破坏、柱底侧移、柱身倾斜、节点拔榫、装修开裂、梁架歪闪、瓦件掉落、填充墙破坏等;而砖石及砖木结构由于承重材料的抗拉、压、剪强度相对较差,容易产生倒塌等严重震害。在此基础上,通过勘查分析方法,获得了古建筑产生震害的主要原因：地震力过大、古建筑缺乏及时保养与加固、施工原因及砖石材料本身强度差的原因等。针对不同的震害原因,提出了相应的抗震加固建议。在上述工作基础上,得出如下结论：为提高古建筑的抗震性能,应加强对古建筑的维护与加固,及时清除各种隐患,将地震产生的破坏减小到最轻的程度。     

张衡地动仪的发明、失传与历史继承

地动仪的发明和失传存在深厚的社会背景.悬挂物对地震的良好反应是诞生科学思想的物质基础.地动仪是对天然验震器的发展,张衡不仅在利用物体惯性测震上,也在检测和记录地震微弱信号上有技术创新,成功测到公元134年12月13日陇西地震.天诫观念把自然现象与社会问题混为一谈,导致张衡晚年和地动仪的悲剧.仪器可能失传于东汉末年,当时发生了洛阳大火、毁铜铸钱、京师搬迁、人口剧减和灵台被毁等极端严重的社会混乱.张衡的科学思想和实践对现代地震学的起步发挥过思想启迪作用.对地动仪的研究需要开展科学实验,学术观点的统一只能建立在科学实验的基础上.     

玉树抗震救灾精神与社会主义核心价值

玉树抗震救灾精神就是大爱同心、众志成城的民族精神,就是坚韧不拔、百折不挠的革命英雄主义精神,就是挑战极限、全心全意为人民服务的精神,就是感恩奋进、自力更生、艰苦奋斗的精神。玉树抗震救灾精神是社会主义核心价值的时代表达,彰显了社会主义核心价值体系的现实要求。