基于岩浆凝固的地壳动力学研究北大核心CSCD

地球在形成之初处于熔融状态,随着时间的推移,地球表面的岩浆不断冷却、凝固,发展成现在的圈层结构,并且地球物质的冷却及液-固转变依然在持续。通过对地震发生后地球日长变化进行统计分析,发现总体上地震后地球自转速率加快。分析认为,这一现象是由于地幔部分岩浆冷却凝固使地壳岩石圈下部体积塌缩所致。由此,建立了一个地壳动力学模型,以解释地壳各板块间的相互作用和相对运动,并且认为地震等地质活动的动力学成因主要是地球内部熔体持续凝固所导致的地壳下部体积收缩、压力减小,在重力作用下,构成地壳的各板块之间的相互作用加剧,原有力学结构失稳,发生大规模岩层错位、断裂,从而引起地震、火山爆发等剧烈的地质活动。通过建立热学模型和力学模型,验证了上述观点。     

基于岩浆凝固的地壳动力学研究

地球在形成之初处于熔融状态,随着时间的推移,地球表面的岩浆不断冷却、凝固,发展成现在的圈层结构,并且地球物质的冷却及液-固转变依然在持续。通过对地震发生后地球日长变化进行统计分析,发现总体上地震后地球自转速率加快。分析认为,这一现象是由于地幔部分岩浆冷却凝固使地壳岩石圈下部体积塌缩所致。由此,建立了一个地壳动力学模型,以解释地壳各板块间的相互作用和相对运动,并且认为地震等地质活动的动力学成因主要是地球内部熔体持续凝固所导致的地壳下部体积收缩、压力减小,在重力作用下,构成地壳的各板块之间的相互作用加剧,原有力学结构失稳,发生大规模岩层错位、断裂,从而引起地震、火山爆发等剧烈的地质活动。通过建立热学模型和力学模型,验证了上述观点。     

科里奥利力对气垫转盘的影响

对气垫转盘无外力矩自转现象的原因进行了探讨,理论分析和实验数据均表明:地球自转而产生的科里奥利力是气垫转盘无外力矩自转的最可能原因.这将为气垫转盘实验的改进提供重要的参考和依据.     

高压下岩浆凝固对岩石圈力学状态的影响

板块构造活动与岩石圈密切相关,是地震等重大地质活动的物理源,但其动力机制尚不清楚。为此,通过分析地球内部处于高压环境的岩浆凝固对岩石圈力学状态的影响,探究板块运动的力源机制。地球作为一个整体不断向外太空散发热量,内部是处于高压高温下的液-固共存状态。自地球形成以来,熔融岩浆的凝固过程持续至今,液-固转变将导致地球内部的密度变化和潜热释放,从而降低刚性岩石圈底部的压力及其支撑力。研究发现,岩石圈的强度不足以支撑其自重,底部的压力(强)波动会使其力学结构失稳。受刚性、脆性岩石圈的约束,地球内部处于高压环境的岩浆凝固必然导致岩石圈力学状态发生变化,在重力作用下,板块之间的相互作用加剧,局部应力积累会超过岩石的强度极限,导致岩石圈内部发生破裂,所积累的应力通过地震等地质活动形式在岩石圈薄弱地带释放,并自我调整以达到新的力学平衡,而板块边界就是岩石圈的最薄弱区域,所以该区域的地震活动频繁发生。上述过程是不断重复的,这就是板块运动驱动力的来源。     

潮汐对地球自转阻滞作用的估计

讨论了潮汐阻滞地球自转的机制,利用一个简化的模型计算了由潮汐引起的地球自转角加速度的数量级,得到了比较满意的结果,并讨论了几个简化假设的合理性,还利用该模型计算了当地球自转速度不再变化时的几个数据.     

超流He的宏观量子特性

196 4年国际计量委员会通过议案 ,以铯原子钟作为守时的基准 :1ｓ =9192 6 31770× (1/ν铯) ,其中ν铯 是13 3 Ｃｓ原子基态超精细结构能级Ｆ1=3和Ｆ2 =4之间的共振跃迁微波频率 .按照现代原子钟的测量 ,地球的自转周期竟然也会发生变化 :一昼夜的长度可能有 0 0 0 2ｓ的上下起伏 .本文所要讨论的是 ,用超流Ｈｅ的位相相干特性探测地球的自转 .想像有一只尺度仅数厘米的汽车轮胎 ,里面充满了超流4 Ｈｅ .在“轮胎”内部用一块隔板将环状的超流体阻断 ,并且在隔板上钻一个直径小于 1μｍ的针孔 .这样 ,便构成了一个单结超流约瑟夫森环——…     

康普顿早期验证地球自转的“水管”实验

对美国著名物理学家A.H.康普顿在大学本科阶段对地球自转的验证性实验进行原理简述,将其与最早证明地球自转的实验——傅科摆实验并行讨论,从实验原理、背景及影响方面对2个实验的差别作简要分析.     

探究太阳从西边升起的条件

太阳系中的八大行星的自转方向大部分都是自西向东,只有金星的自转方向是自东向西.所以在金星上看太阳是从西边升起的,而在其他七颗行星上看太阳都是从东边升起的.现实生活中,我们说太阳从西边升起来了,一般指事情不可能发生.而在某些特定的条件下,在地球上有没有可能看到太阳从西     

地表柯石英的实验室模拟合成及其形成机制的研究

 静高压合成柯石英的压力和温度的实验条件是提出地球板块折返假说的基础，然而，静高压没有反映局部碰撞和剪切应力的因素。考虑这些因素，提出了一种利用高能机械球磨与静高压相结合的、可以模拟地表柯石英合成的实验室研究方法，发现了一种由机械碰撞引起的α-石英中间亚稳相，其静高压致晶化成柯石英的条件为3.0 GPa、923 K、<1.0 min。如果沿袭传统的板块折返假设，对应此条件的板块俯冲深度应比Jr.L.Coes的结果浅20 km。发现了10 s量级的柯石英的短时间快速合成现象。由本方法合成的柯石英的Raman峰，涵盖了以前得到的天然柯石英和人工合成的柯石英的Raman信息。阐明了由本方法合成的柯石英在地质科学上的涵义，并提出了另一种可能的地表柯石英形成机制。     

地球内部物质运动的物理学和化学问题研讨会简讯

地球内部物质运动的物理学和化学问题研讨会于 2 0 0 1年 1月 2 0日在中国高等科学技术中心举行 .出席研讨会的有来自南开大学、北京大学、中国科学院高能物理研究所、化学研究所、国家地震局地质研究所、中国地质学会、中国地质科学院地质研究所、中国地质科学院矿产资源研究所、国土资源部(原地质矿产部 )地球化学动力学开放实验室等单位的 16名代表 .此次研讨会同时是国土资源部地球化学动力学开放实验室学术年会 .研讨会不仅安排了学术报告 ,而且在发言过程中展开了热烈的讨论 ,内容涉及地球内部极端条件下的物质基本性质 ,高温高压对物…     

基于多光谱遥感的青海玉树地震震害监测与评估

青海玉树7.1级地震使当地人民群众的生命和财产受到严重损失.利用多光谱遥感技术获取数据范围广、手段多等优势,以地震前后不同空间分辨率的航空和航天多光谱遥感影像作数据源,通过遥感和GIS技术的应用,对玉树地震的构造背景,地震重灾区的房屋建筑倒塌、场地震害、生命线工程等震害信息进行遥感监测和分析,并对监测区内毁坏严重的土木...     

高分辨率多光谱的芦山地震次生地质灾害遥感监测与评估

2013年4月20日芦山7.0级大地震发生后,产生大面积滑坡、崩塌、碎屑流等次生地质灾害,造成大量人员财产损失,并严重阻碍了应急救援和灾后重建工作的顺利开展。利用快速获取的震前和震后航空、航天等多源遥感数据、地形地貌和地质构造数据,首先结合次生地质灾害在高分辨率多光谱影像上的形态、结构和纹理特征,对地震重灾区次生地质灾害的数量和空间分布进行了有效监测。结果显示：芦山县、宝兴县和天全县次生地质灾害最为严重,各有164处、126处和71处大型次生地质灾害点。并结合GIS技术对这些次生地质灾害的空间分布规律,特别是同区域地质构造、烈度和地形地貌之间的关系进行了综合分析和评估。评估结果显示：在监测区存在四个次生地质灾害高发区,其中一个聚集在震中6公里范围内,其他三个沿本区域两个主要地质断层分布;超过97%的次生地质灾害位于烈度Ⅶ～Ⅳ度、坡度25°～50°且海拔800～2 000 m之间的区域。最后结合震害遥感监测评估结果,对震后恢复重建规划及实施提出建议。     

减轻地震灾害的物理学问题

减轻地震灾害的研究通常包括地震危险性评估、地震危害预测、地震灾害的减轻三个环节．物理学在减轻地震灾害的研究与应用中具有重要意义．文章从强地面运动与地震的工程灾害、复杂系统与地震的社会灾害、地球应力场的变化与地震预测等三个不同的侧面，介绍了在减轻地震灾害的实际工作中提出的一些重要的物理问题．这些问题既是目前地震学家、工程地震学家和地震工程师普遍关注的基础科学问题，也同时与当代物理学研究的一些前沿领域紧密地联系在一起．     

2 billion year old natural analogs for nuclear waste disposal: the natural nuclear fission reactors in Gabon (Africa)

Two billion years ago, the increase of oxygen in atmosphere and the high ²³⁵U/²³⁸U uranium ratio (>3%) made possible the occurrence of natural nuclear reactors on Earth. These reactors are considered to be a good natural analogue for nuclear waste disposal. Their preservation during such a long period of time is mainly due to the geological stability of the site, the occurrence of clays surrounding the reactors and acting as an impermeable shield, and the occurrence of organic matter that maintained the environment in reducing conditions, favourable for the stability of uraninite. Hydrogeochemical studies and modelling have shown the complexity of the geochemical system at Oklo and Bangombé (Gabon) and the lack of precise data about uranium and fission products retention and migration mechanisms in geological environments. To cite this article: F. Gauthier-Lafaye, C. R. Physique 3 (2002) 839–849.     

New features of the Moon revealed and identified by CLTM-s01

Previous analyses showed a clear asymmetry in the topography, geological material distribution, and crustal thickness between the nearside and farside of the Moon. Lunar detecting data, such as topography and gravity, have made it possible to interpret this hemisphere dichotomy. The high-resolution lunar topographic model CLTM-s01 has revealed that there still exist four unknown features, namely, quasi-impact basin Sternfeld-Lewis (20°S, 232°E), confirmed impact basin Fitzgerald-Jackson (25°N, 191°E), crater Wugang (13°N, 189°E) and volcanic deposited highland Yutu (14°N, 308°E). Furthermore, we analyzed and identified about eleven large-scale impact basins that have been proposed since 1994, and classified them according to their circular characteristics.     

Origin of Starting Earthquakes under Complete Coupling of the Lithosphere Plates and a Base

The boundary problem of rigid coupling of lithospheric plates modeled by Kirchhoff plates with a base represented by a three-dimensional deformable layered medium is considered. The possibility of occurrence of a starting earthquake in such a block structure is investigated. For this purpose, two states of this medium in the static mode are considered. In the first case, the semi-infinite lithospheric plates in the form of half-planes are at a distance so that the distance between the end faces is different from zero. In the second case, the lithospheric plates come together to zero spacing between them. Calculations have shown that in this case more complex movements of the Earth’s surface are possible. Among such movements are the cases described in our previous publications [1, 2].     

Magnetoelastic sensors and geophones for vector measurements in geoacoustics

The process of earthquake origination is associated with the action of intrinsic forces of both natural and artificial origin, which substantially change the stress fields in the Earth’s crust. These slow movements are accompanied by acoustic noise (acoustic emission). Broadband measurements of acoustic emission from naturally deposited rocks is an effective tool for an instrumental monitoring of the Earth’s crust that is aimed at earthquake forecasting. Considerable advances in this direction have become possible with the development of a new type of acoustic sensors with a velaccelerometric characteristic, for which the sensitivity increases by three orders of magnitude when the frequency increases tenfold. In geoacoustic observation systems, this makes it possible to considerably expand the amplitude-frequency range of investigation and creates new opportunities for a detailed analysis of the earthquake origination process. The results of observations of high-frequency underground acoustic noise, which were carried out in various regions of the Earth, in wells and edits, with the use of hardware/software systems containing new broadband magnetoelastic acoustic geophones, have confirmed experimentally its relation to slow deformations in the Earth’s crust. It turns out that underground hum in the frequency range from 16 to 2000 Hz contains new independent information on changes in the stressed state and is a sensitive indicator of tectonic and tidal movements. Practical investigations performed by researchers from the Institute of Volcanology, Far East Division of the Russian Academy of Sciences, in Petropavlovsk-Kamchatski have convincingly proved that acoustic noise variation may serve as a reliable seismic alert. The present publication is devoted to the history of the development and application of magnetoelastic geophones.     

Earthquake forecast via neutrino tomography

We discuss the possibility of forecasting earthquakes by means of (anti)neutrino tomography. An- tineutrinos emitted from reactors are used as a probe. As the antineutrinos traverse through a region prone to earthquakes, observable variations in the matter effect on the antineutrino oscillation would provide a tomog- raphy of the vicinity of the region. In this preliminary work, we adopt a simplified model for the geometrical profile and matter density in a fault zone. We calculate the survival probability of electron antineutrinos for cases without and with an anomalous accumulation of electrons which can be considered as a clear signal of the coming earthquake, at the geological region with a fault zone, and find that the variation may reach as much as 3% for ν<,e> emitted from a reactor. The case for a ν<,e> beam from a neutrino factory is also investigated, and it is noted that, because of the typically high energy associated with such neutrinos, the oscillation length is too large and the resultant variation is not practically observable. Our conclusion is that with the present reactor facilities and detection techniques, it is still a difficult task to make an earthquake forecast using such a scheme, though it seems to be possible from a theoretical point of view while ignoring some uncertainties. However, with the development of the geology, especially the knowledge about the fault zone, and with the improvement of the detection techniques, etc., there is hope that a medium-term earthquake forecast would be feasible.     

准连续调制激光吸收谱测量封闭室内O2浓度的研究

在开采煤矿的生产活动中,遇到煤矿爆炸或地震、地质等自然灾害,会导致坍塌、掩埋、堆积等情形,进而形成复杂的封闭环境。如果发生人员被困等突发情况,破灾救援、挽救生命工作显得至关重要。封闭环境中O₂的浓度随时间的变化直接威胁到被困人员的生命安全,及时掌握被困人员所处环境的O₂浓度变化对破灾救援机器人作业实施有着非常重要的指导意义。为准确测量O₂的浓度,以封闭室内O₂为研究对象,综合应用可调谐二极管激光吸收光谱(TDLAS)技术和波长调制光谱(WMS)技术,设计了一套准连续调制激光吸收谱实验测量O₂浓度系统,对24 h封闭室内O₂的浓度随时间变化情况进行测量研究。实验结果表明,封闭室内O₂的浓度受到室内人员活动的影响,准连续调制激光吸收谱测量方法可以准确测量封闭室内的氧气变化。     

The “small-world” topology of rock fracture networks

In this contribution we show that natural rock fracture networks, acting as media for the delivery of a variety of geological fluids, can be studied by using the principles of complex systems. Natural networks at different length scales (from the metre to the micrometer) have been analysed by evaluating their connectivity at global and local scale and results show that they share topological properties of “small-worlds”, a class of networks characterised by high global and local transport efficiency. This may have important geological implications for a variety of geological processes related to the transfer of fluids within the Earth, from the delivery of magmas to the Earth surface to the dispersion of pollutants in shallow aquifers.