Results from Kodaikanal synoptic observations

The synoptic observations of Kodaikanal form one of the longest unbroken solar data from the beginning of the 20th century to the present day, and consists of the white light and monochromatic images of the sun. In this review, I shall discuss the results of the investigations in two areas using these data: (i) Tilt angles of the magnetic axes of bipolar spot groups, and (ii) structure and dynamics of large scale unipolar magnetic regions on the solar surface. The observed properties and patterns of behaviour of the tilt angles can be used as effective diagnostics to infer the physical conditions in the subsurface layers of the sun, and thus get an insight into the physical effects that act on the rising magnetic flux tubes during their journey through the convection zone to the surface. The second topic of discussion here, namely, the studies of the dynamics of unipolar regions over several solar cycles, show that the global solar activity has a high latitude component which manifests in the form of polar faculae, in addition to the well known sunspot activity at the middle and low latitudes. This raises the question about the origin of this high latitude component.     

Determination of the cleat angle distribution of the RECOPOL coal seams, using CT-scans and image analysis on drilling cuttings and coal blocks

Cleat orientation, cleat frequency and cleat angle distribution of deep coal seams are only available by the use of drilling cores and from coal mine samples. Coal drilling cuttings are a cheap and fast alternative to measure cleat angle distributions with the use of image analysis techniques. In this study oriented coal samples and drilling cuttings of the RECOPOL field experiment are compared and used to explain and validate the proposed method. In other words, cleat angle distributions from drilling cuttings are measured by image analysis. The geological framework of the polish coals is described. The image analysis methodologies for the measurement of fracture faces of cuttings and from CT-scan images, derived from these coals, are explained. The results of the methods on the cuttings are compared with cleat orientation distributions from CT-scans and artificial fragments from coal blocks of the same seams. These evaluations show high agreements between the methods. The cleat angle distributions of drilling cuttings of four seams are compared with the cleat orientation distributions of a regional structural geological study. The high correlation in this study shows that cleat angle distributions of coal seams can be used as input parameters for reservoir modelling.     

基于波场传播方向的波动方程偏移有效去噪方法(英文)

本文研究分析了双程波波动方程偏移成像中广泛存在的三种主要噪声,特别是针对过去研究中没能很好解决的存在于高速盐丘悬垂边界附近的射线状噪声,提出了基于优化成像条件的有效去噪方法。射线状噪声主要来自于震源一侧波场的下行透射波分量和接收阵列一侧波场的上行散射波互相关成像。这一部分能量具有较强的互相关性,但并不携带真实的反射面信息。它广泛存在叠前偏移成像中,与信号在强度上同量级。多数情况下偏移成像中的相关噪声由方向性传播的波场能量产生。利用波场梯度得到的波场传播角度,可以分离出噪声对应的波场能量,并在成像条件中减去。采用这一方法可以有效地去除多种噪声,包括直达波噪声、散射波噪声和射线状噪声。该去噪方法不依赖波场外推算子,在需要时可以方便地运用到几乎所有的波动方程偏移中去。并且该去噪方法针对噪声的物理根源,对信号的损害很小。对去噪后的偏移成像结果额外地进行波数域滤波处理,可以进一步提高叠加图像的质量。这一去噪方法在超广角单程波偏移成像中取得良好效果,我们同时期待其在其他双程波波动方程偏移特别是逆时偏移(RTM)中的成功运用。     

不同倾角组合煤岩体的强度与破坏机制研究

对4种不同倾角组合煤岩体进行了试验和数值模拟研究,获得了单轴和三轴压缩条件下组合煤岩体的宏观破坏机制,并分析了煤岩组合体中煤、岩不同倾角交界面对煤岩组合体整体变形破坏的影响。研究表明,单轴荷载条件下煤岩组合体的破坏强度随着组合倾角的增加而出现先微小减小,而后迅速减小;同种倾角条件下,煤岩组合体的破坏强度随着围压的升高而逐渐升高,并且煤岩组合体的倾角越小,破坏强度升高的速率越慢,而倾角越大,升高的速率越快,可见围压对于大倾角裂隙的抑制作用更明显。通过三轴试验获得了煤岩组合体整体结构的黏聚力和内摩擦角,其中组合体黏聚力随着倾角的增加而逐渐减小,但内摩擦角变化规律不明显。通过扩展有限元对试验结果进行了模拟验证,发现随着倾角由0°增加到60°,外力功、屈服应力和弹性应变能都在下降,当倾角超过45°～50°后,外力功和屈服应力将与弹性应变能出现背离,这是煤岩组合体的变形破坏机制由剪切变形机制逐渐转化为界面滑移破坏机制重要标志。     

“照亮”地下

本文介绍利用地震角度偏移法实现照亮地下的理论构想,并做了大量的研究工作,说明地震波角度偏移法在地下空间探测中的巨大作用和应用前景.研究中利用仿生学眼睛的功能,阐述了照亮地下的理论和方法技术,特别研究了眼睛的形觉、光觉、色觉、立体觉与地下空间探测的对比关系.最后结合研究的实测结果说明照亮地下理论的可实现性及效果.     

Constraining the anisotropy structure of the crust by joint inversion of seismic reflection travel times and wave polarizations

In the context of wide-angle seismic profiling, the determination of the physical properties of the Earth crust, such as the elastic layer depth and seismic velocity, is often performed by inversion of P- and/or S-phases propagation data supplying the geometry of the medium (reflector depths) or any other structural parameter (P- or S-wave velocity, density...). Moreover, the inversion for velocity structure and interfaces is commonly performed using only seismic reflection travel times and/or crustal phase amplitudes in isotropic media. But it is very important to utilize more available information to constrain the non-uniqueness of the solution. In this paper, we present a simultaneous inversion method of seismic reflection travel times and polarizations data of transient elastic waves in stratified media to reconstruct not only layer depth and vertical P-wave velocity but also the anisotropy feature of the crust based on the estimation of the Thomsen’s parameters. We carry out a checking with synthetic data, comparing the inversion results obtained by anisotropic travel-time inversion to the results derived by joint inversion of seismic reflection travel times and polarizations data. The comparison proves that the first procedure leads to biased anisotropic models, while the second one fits nearly the real model. This makes the joint inversion method feasible. Finally, we investigate the geometry, P-wave velocity structure and anisotropy of the crust beneath Southeastern China by applying the proposed inversion method to previously acquired wide-angle seismic data. In this case, the anisotropy signature provides clear evidence that the Jiangshan-Shaoxing fault is the natural boundary between the Yangtze and Cathaysia blocks.     

RT模式下刚性挡墙土压力计算方法研究

针对绕墙顶向外转动的刚性挡土墙,提出一种土压力计算方法。根据土体渐进破坏机理,考虑土拱效应,建立了填土内摩擦角及墙土接触面上外摩擦角的发挥与土体位移的非线性关系,并根据初始应力条件确定初始内摩擦角。采用改进的水平层分析法计算各转角下的土压力分布,并得到土压力合力大小及其作用点的计算公式。通过比较,不同转角下土压力强度、合力大小以及作用点计算值与模型试验实测结果接近。     

自适应空间分区裂步傅立叶偏移方法

本文提出了一种新的偏移方法——自适应空间分区裂步傅立叶（ASDSSF）偏移方法。该方法将剥层相位移方法的思想推广到裂步傅立叶偏移方法，使之当速度场出现强间断时也能精确而有效地成像。原理上ASDSSF偏移属于多参考慢度（MRS）偏移方法，本文的重点是，在不损失精度的同时选取比同类MRS偏移方法更少的参考慢度。我们根据全局速度函数的变化和误差控制参数来选择参考慢度，同一个参考慢度所对应的速度构成一个分区，每一个空间分区可以由几个空间上不连续的子分区组成，从而有效地减小了参考慢度的个数。每一延拓步的参考慢度以及参考慢度的个数和如何构建分区都是根据速度函数自动生成，因此更为合理。为了消除速度场强间断产生的人为噪音，设计了简单有效的f-k域的光滑滤波。我们对一个生成的二维叠前模型和SEG／EAEG盐丘模型进行了试算。     

Textural Maturity of Cumulates: a Record of Chamber Filling, Liquidus Assemblage, Cooling Rate and Large-scale Convection in Mafic Layered Intrusions

Textural maturity describes the extent to which a rock has evolvedfrom the initial reaction-controlled texture towards texturalequilibrium controlled by the minimization of interfacial energy.Solidification in a magma chamber results in the formation ofan impingement texture by the random juxtaposition of planar-sidedgrains. Orthocumulates, in which the initial melt-filled poresare pseudomorphed by later-crystallizing phases, have an ophiticor intersertal texture immediately after complete solidification,which then evolves towards solid-state equilibrium by roundingof initially planar grain boundaries and an increase in themedian dihedral angle subtended at the junctions of two primocrysticgrains with the interstitial phase. The bulk of the increasein angle occurs just below the solidus temperature in kilometre-scalemafic plutons. Quantification of textural maturity via measurementof dihedral angle populations in troctolitic and gabbroic cumulatesfrom the Rum Eastern Layered Intrusion and the Skaergaard Intrusiondemonstrates that the rocks preserve a record of thermal eventsrelated to magma chamber replenishment and the onset of chamber-wideconvection. Textural maturity is also a function of the liquidusphase assemblage: for systems in which only olivine and plagioclaseare liquidus (i.e. cumulus) phases in the main magma body abovethe crystal mush, the texture is significantly less mature thanthat in systems in which clinopyroxene is an additional liquidusphase. The difference in textural maturity reflects differencesin the cooling and solidification rate, and demonstrates directlythat the liquidus phase assemblage plays a role in determiningthe thermal history of plutons. KEY WORDS: cumulates; dihedral angles; Rum; Skaergaard; textures     

Rotation of the Earth as a Triaxial Rigid Body

The Earth is taken as a triaxial rigid body, which rotates freely in the Euclidian space. The starting equations are the Euler dynamic equations, with A smaller than B and B smaller than C. The Euler equations are solved, and the numerical results are provided. In the calculations, the following parameters are used: (C-B)/A=0.003 273 53; (B-A)/C=0.000 021 96; (C-A)/B=0.003 295 49, and the mean angular velocity of the Earth's rotation, ω =0.000 072 921 15 rad/s. Calculations show that, besides the self-rotation of the Earth and the free Euler procession of its rotation, there exists the free nutation: the nutation angle, or the angle between the Earth's momentary rotation axis and the mean axis that periodically change with time. The free nutation is investigated.