COMPREHENSIVE ANALYSIS OF THE MACRO- AND MICRO-PHYSICAL CHARACTERISTICS OF DENSE FOG IN THE AREA SOUTH OF THE NANLING MOUNTAINS

Using the composite field observational data collected in the area south of the Nanling Mts. and numerical modeling, the seasonal features of dense fog and visibility, fog drop spectrum and physical concept of fog forming have been analyzed. The occurring frequency of low visibility（≤200 m） is very high with a mean of 24.7%, a maximum of 41.8% from the end of autumn to winter and next spring. The fog processes that occur in the area south of the Nanling Mts. in spring and winter result from the interactions of complicated micro-physical processes, the local terrain, water vapor transportation and the influencing weather system. The fog processes are arisen from advection or windward slope, which is much different from the radiation fog. Cooling condensation due to the air lifted by the local mountain plays an important role in fog formation. Windward slope of the mountain is favorable to the fog formation. Dense fog can occur at lower altitudes in the windward slope of mountain, resulting in the lower visibility. The fog is mainly of small-drop spectrum with smaller number-density than that of urban fog, and its drop spectrum has descending trend in the section of smaller diameter. The inverse relationship between fog water content and visibility is the best among several relationships of micro-variables. In addition to micro-physical processes of fog body itself, the motion of irregular climbing and crossing over hillside while the fog body is being transported by the wind are also important reasons for the fluctuation of micro-physical parameters such as fog water content.     

青藏高原北缘变形动力学研究的一些新认识

地质矿产部“八五”重点深部项目“青藏高原北缘变形动力学研究”，通过对青藏高原北缘综合地质调查和研究(期间共完成40条、总长约1000km的路线剖面观察)，获得了一些重要地质信息和认识。     

2016年台湾美浓MW6.4地震震源参数的InSAR和GPS反演

2016年2月6日台湾西南部高雄市美浓区发生了M_W6.4地震.本文结合ALOS2卫星升降轨、Sentinel-1A升轨SAR数据,采用两轨差分干涉技术获取了该区域的同震形变场,形变结果表明震中西北部以抬升为主,最大视线向形变量约为11.2 cm.基于均匀位错模型和多峰值粒子群（MPSO）算法,利用InSAR和GPS形变数据联合反演了美浓地震的断层几何参数,结果表明震源中心位于22.920°N,120.420°E,深度约12 km,发震断层长度约15 km,走向角307°,倾角16.5°,平均滑动角为51.5°,此次地震是以逆冲倾滑兼左旋走滑的破裂模式.利用格网迭代搜索法得到最优倾角为15.7°,GPS和InSAR最优权比为18：1,最优平滑因子为0.06.基于非均匀位错模型,利用非负最小二乘方法进行线性反演,结果显示最大倾滑和走滑量分别为51.7 cm和55.3 cm,对应矩震级为M_W6.38,略小于GCMT （M_W6.4）的结果.通过与已有文献的比较和对该区域断层构造的分析,发现美浓地震的发震断层为单一断层的解释更为合理,我们推测发震断层是位于左镇、后甲里等断层之间的一条东南-西北走向往东北倾斜的盲断层,并初步推测2010年M_W6.3甲仙地震也同该断层有关.     

四川盆地深部地壳结构——深地震反射剖面探测

四川盆地位于扬子地块的西北部,被褶皱构造带所围绕,受周缘构造带的侧向挤压作用,盆地卷入了多期次和多边界的构造变形,为开展盆山耦合作用及多边界、多期次构造叠加与复合关系的研究提供了不可多得的理想野外实验室.为揭示四川盆地地壳结构,本文通过对3条不同时间采集的深地震反射剖面数据进行拼接联线处理,获得跨越四川盆地的330 km深地震反射偏移成果剖面,揭示了四川盆地地壳上地幔细结构:沉积层从西北向东南逐渐变薄,在龙门山前沉积层厚度超过15 km,在华蓥山下沉积层减薄到~8 km,且褶皱变形形成华蓥山薄皮褶皱冲断带;莫霍面出现在13~15 s(双程走时),埋深约40~45 km;并发现从下地壳延伸至地幔的东南向的倾斜反射,从13 s向下延伸至18 s,结合四川盆地及其周边地区其他地球物理和地球化学花岗岩同位素年龄等资料,我们认为这些倾斜反射层是扬子克拉通地台西北缘发生的新元古代俯冲的遗迹.     

CSAMT法三维分辨能力及其物理机制

随着CSAMT法探测应用需求的日益增多,其分辨能力及其物理机制的研究成为人们不得不面对的问题.在CSAMT勘探中,几何效应、电流效应和感应效应是引起电磁场变化的三种物理机制,本文详细介绍了与地下电性结构密切相关的电流效应和感应效应.首先,利用CSAMT法对100 m×100 m×100 m的异常体进行了探测,研究表明存在两个畸变区域.利用电流效应对存在的两个畸变区域进行了解释,进一步研究表明当收发距为10 km时电流效应占据主要地位,感应效应位居次要地位,当收发距增大时电流效应比重下降,感应效应比重增大.选取坐标原点位于电偶极子中心,x方向为电偶极矩方向,z轴垂直向下,随后,研究了CSAMT法对异常体沿x、y及z方向长度变化时的探测灵敏度,研究表明CSAMT法对异常体沿x方向的变化最为灵敏、y方向变化次之、z方向最为迟钝,最后对以上现象给出了解析.     

鲁科一井上白垩统沉积岩岩石磁学和天然剩磁分析:兼论利用剩磁方向恢复钻孔岩芯原始方位的可行性

本文对"鲁科一井"(CCSD-LK-Ⅰ)768.9~1112.3m之间的上白垩统沉积岩样品进行了岩石磁学、磁化率各向异性(AMS)以及天然剩磁组分的研究.在此基础上,分析了利用特征剩磁(ChRM)和黏滞剩磁(VRM)方向恢复岩芯原始方位的可行性.三轴等温剩磁热退磁曲线、磁滞回线、反向场退磁曲线、一阶反转曲线等岩石磁学测量结果表明,沉积岩的主要载磁矿物为磁铁矿和赤铁矿.335块样品的AMS测量结果表明磁化率椭球主轴的最大轴K1和中间轴K2与水平面夹角较小,最小轴K3接近垂直于水平面分布,说明沉积岩保留了原始沉积磁组构特征.系统热退磁实验表明,多数样品在25~350℃和500~690℃温度段分别获得VRM和ChRM分量.利用ChRM偏角方向,并考虑构造旋转量校正,对VRM偏角方向进行恢复,Fisher统计得到DVRM=-1.3°,IVRM=59.6°,与当地现代地磁场方向(D=-6.7°,I=53.9°)基本一致.用ChRM偏角方向对磁化率主轴K1偏角方向进行校正,校正的结果为:D_(ch_K1)=349.2°,I_(ch_K1)=-0.7°.本文研究结果对于地质勘探中利用古地磁学方法恢复钻孔岩芯原始方位具有一定参考意义.     

Spatial behaviour of Rayleigh waves in layered half‐spaces under active surface sources

In the free state, Rayleigh waves are assumed to travel in the form of planar wavefronts. Under such an assumption, the propagation behaviour of the modes of Rayleigh waves in layered half‐spaces is only frequency dependent. The frequency behaviour, which is often termed as dispersion, is determined by the shear wave velocity profile of layered soils within the depth related to wavelength (or frequency). According to this characteristic, the shear wave velocity profile can be back‐analysed from the dispersion. The technique is widely used in the surface wave testing. However, the wavefronts of Rayleigh waves activated by the surface sources are non‐planar. The geometric discrepancy could result in Rayleigh waves manifesting distance‐dependent behaviour, which is referred to as spatial behaviour in this paper. Conventional analysis ignoring this spatial behaviour could introduce unexpected errors. In order to take the effects of sources on the propagation behaviour into account, a new mathematical model is established for Rayleigh waves in layered elastic media under vertical disc‐like surface sources using the thin‐layer method. The spatial behaviour of the activated modes and the apparent phase velocity, which is the propagation velocity of Rayleigh waves superposed by the multiple modes, are then analysed. Aspects of the spatial behaviour investigated in this paper include the equilibrium path, the particle orbit, and the geometric attenuation of the activated Rayleigh waves. The results presented in this paper can provide some guidelines for developing new inverse mathematical models and algorithms.     

K型加强节点承载力及滞回性能分析

K型相贯节点区域容易出现主管管壁的局部屈曲与撕裂,可以采用主管与内套管之间夹层灌混凝土的方法进行加强。采用有限元软件ANSYS,对加强前后节点的静力极限承载力和滞回性能进行分析。结果表明:在主管与内套管之间夹层灌混凝土可有效改善节点的破坏模式,减小节点附近的应力集中问题,同时增强节点的刚度与承载力;无加强节点滞回曲线较为丰满,承载力下降相对平缓,但和加强节点比较,承载力相差明显;减小内套管的尺寸在一定程度上可以提高节点的极限承载力。     

前板可旋转的双垂板结构水动力特性的理论研究

振荡水柱波能转换装置的最大转换效率往往受到腔内水柱共振机制的直接影响。通过对装置的基本结构进行简化,提出了一种前墙可绕固定轴旋转的双垂板式结构系统,旨在通过前墙的旋转运动进一步加剧水柱的振荡,从而对腔内水柱的共振机制进行调节和控制。基于线性波理论,采用匹配特征函数展开法对波浪与双垂板结构的相互作用进行理论研究,针对流场在结构物尖角附近的奇异性特征,将公共界面上的速度分布基于切比雪夫多项式近似展开,并应用区域间的速度与压力连续条件进行求解。通过分析结构的几何参数对反射透射系数、平均波面高程、前墙旋转振幅以及前墙与水面间相位差的影响,深究其共振机理,为振荡水柱波能转换装置的效率优化机制提供理论依据。结果表明,在所研究的波浪频率范围内,前墙的自由旋转运动会加剧板间的平均波面高程,应用于波浪能转换装置中能进一步拓宽高效频率带宽。     

Direct Conservative Domain in the Continuous Galerkin Method for Groundwater Models

The continuous Galerkin finite element method is commonly considered locally nonconservative because a single element with fluxes computed directly from its potential distribution is unable to conserve its mass and fluxes across edges that are discontinuous. Some literature sources have demonstrated that the continuous Galerkin method can be locally conservative with postprocessed fluxes. This paper proposes the concept of a direct conservative domain (DCD), which could conserve mass when fluxes are computed directly from the potential distribution. Also presented here is a method for modifying the advection fluxes to obtain different conservative domains from the DCDs. Furthermore, DCDs are used to analyze the local conservation of several postprocessing algorithms, for which DCDs provide the theoretical basis. The local conservation of DCDs and the proposed method are illustrated and verified by using a hypothetical 2‐D model.