地震前兆群体空间非均匀性指标Cv值及其应用问题探讨

Cv值是描述前兆分布非均匀性的一个有效指标。不同观测指标获取的震前Cv值异常证明了该方法预测地震的有效性。然而Cv值与观测指标的时间(或空间)分布形式(如周期分布、准周期分布、泊松分布、成丛分布等)并不是简单的对应关系。中在回顾Cv值研究与应用进展的基础上，对Cv值与其分布特征的关系进行了深入分析，指出了应用中存在的问题，从而加深对Cv值物理意义的理解。并给出了Cv值识别前兆群体异常的判别法则。     

岩石非均质程度对水压致裂地应力测试方法影响的分析与讨论

准确揭示原位地应力状态,对地下工程开挖支护设计和长期稳定性分析等具有十分重要的意义。利用水压致裂技术开展了纱岭金矿主竖井地应力测试工作,获得了20个测段地应力状态;室内进行了主竖井测试孔岩芯的岩石力学试验,包括巴西劈裂试验、单轴压缩试验及声发射监测试验,获得了岩石空间非均质度和强度分布特征,并分析了岩石非均质度与水压致裂测试结果的关系。结果表明：主应力大小随测量深度近似呈线性增大,测试孔的最大水平主应力值为20.78~45.20 MPa,最小水平主应力值为14.94~35.33 MPa,平均最大水平主应力方向为 NW65°;测试孔岩芯各层位非均质度不同,变辉长岩非均质度系数为0.1~0.3,且岩石不同强度条件下声发射信号数量变化不显著,岩石离散度较小,花岗岩非均质度系数最高,可达1.0,以加载后期强相破裂产生的声发射信号为主;岩石非均质度影响水压致裂裂纹的扩展方向,扩展方向和最大水平主应力方向的夹角$\varphi $影响着最大、最小水平主应力的测量结果,且对最小水平主应力的影响尤为显著。分析水压致裂测量结果与岩石性质之间的关系,对精确探测非均质地层的地应力场分布规律具有一定的指导作用。     

三维激光扫描点密度不均匀性对地形建模精度的影响研究

三维激光扫描技术获取的扫描点由于密度的不均匀性可能导致所建立的模型不能准确地反映实体的形态变化。本文通过建立严格的数学曲面模型,由曲面模型生成原始采样数据,在生成的原始数据上进行重采样作为实验数据,通过Delaunay三角形建立格网模型,定量分析密度对建模精度的影响。     

Thermohaline structure inhomogeneity associated with polynia at the northern margin of Emery Ice-shelf

Based on the hydrographic data in austral summer during the 22nd Antarctic Expedition of China(2005/2006),some features can be found about the northern margin of Emery ice shelf as follows.The heat content in the surface layer(0-50 m) at the eastern end and the western end of the ice-shelf margin is much higher than that at the middle.The upper mixing-layer depth and the seasonal thermocline depth at the middle of the ice-shelf northern margin are much shallower than those at the both ends.However there is much less difference between the middle and the ends in the bottom layer.The remote sensing photos show that the inhomogeneity in the surface-layer water is closely related to the spatial distribution of the floes and polynia in the area.     

3-D velocity images of the crust and upper mantle of the Tianshan area

（胥颐，朱介寿，刘志坚，张华卿，朱燕）３－ＤｖｅｌｏｃｉｔｙｉｍａｇｅｓｏｆｔｈｅｃｒｕｓｔａｎｄｕｐｐｅｒｍａｎｔｌｅｏｆｔｈｅＴｉａｎｓｈａｎａｒｅａ￥ＹｉＸＵ；Ｊｉｅ－ＳｈｏｕＺＨＵ；Ｚｈｉ－ＪｉａｎＬＩＵ；Ｈｕａ－ＱｉｎｇＺＨＡＮＧａｎｄＹａ...     

Inhomogeneities in the circumstellar envelope of the A0E herbig star AB aur

Simultaneous high-resolution spectroscopy in H andUBVRI polarimetric observations are proposed as an effective method for the search for circumstellar inhomogeneities in A0-type Herbig stars. The new results for AB Aur are presented as a successful example of the use of this method. The analysis of about 100 CCD H profiles (R = 30 000) and more than 150 polarimetric measurements obtained in January, 1994 allowed to discover a long-lived stream-like inhomogeneity in the circumstellar gaseous envelope.     

1992年6月26日Hα耀斑后环的不均匀性和物质运动的可能解释

本文利用电流不稳定性线性理论讨论了１９９２年６月２５日至２６日耀斑后环中出现不均匀“结”状结构（“ｋｎｏｔ”或“ｂｌｏｂ”）的可能性,并且在同时考虑重力、磁力和环顶物质下落初速的情况下,理论计算了１９９２年６月２６日Ｈα耀斑后环物质运动的规律。理论计算与观测求得的视向速度随高度分布的曲线基本符合。     

Acceleration of near-field scattering from an inhomogeneous spherical shell

The three dimensional scattering of near-field, from a point source, is studied for acceleration in the time domain. The perturbation method is applied to define the acceleration for the first order scattering from a weak inhomogeneity in a homogeneous surrounding. A body force, arising from the interaction between the primary waves and the inhomogeneity, acts as the source generating the scattered motion. The acceleration of scattered waves is related to the velocity and density fluctuations of the inhomogeneity. No restrictions are placed on the inhomogeneity size or locations of the source and receiver. Decoupling of scattered motion enables the identification of different phases. Integral expressions are derived for the scattering acceleration due to the incidence of near-field wave (from an impulsive point force) at a radially inhomogeneous volume element. These integrals are solved further for scattering from an inhomogeneous spherical shell. The accelerations for back scattering are obtained as a special case. These accelerations are simple analytically solvable expressions in closed form. Only spherical asymmetry ofP wave velocity inhomogeneity can affect the scatteredS acceleration. ScatteredP acceleration is affected by the gradient ofS wave velocity inhomogeneity. The back scattering of near-field from a spherical shell, is independent of radial inhomogeneity ofP wave velocity. Inhomogeneity with smoothly perturbedS wave velocity does not back-scatter any acceleration. Accelerations are computed numerically for scattering from a part of inhomogeneous spherical shell. Hypothetical models are considered to study the effects of the distances of spherical shell from source, receiver, its thickness and its position relative to the direction of impulsive force.     

Grounded-source transientE-field modeling of a shallow resistive layer with 3-D inhomogeneity

There is growing interest in the use of transient electromagnetic (TEM) sounding for shallow geotechnical, environmental and groundwater investigations. Two commonly used transmitterreceiver configurations for TEM sounding are 1) loop-loop or its variation, in-loop configuration and 2) wire-loop configuration. The less common configuration of a horizontal electric dipole (HED) transmitter and receiver is treated in this study and called wire-wire configuration.Two important problems of shallow investigation in hard and soft rocks respectively are, defining 1) a fractured/fissured zone of medium resistivity, sandwiched between an overlying surface weathered rock of low resistivity and an underlying fresh compact rock of high resistivity and 2) a body of resistive sand buried in conductive clay. Lateral change in the middle layer resistivity is modeled by including a 3-D body of anomalous resistivity. The effect of perturbing the resistivity of the 3-D inclusion and the host middle layer for the wire-wire configuration is compared with that of the commonly used loop-loop configuration. The wire-wire configuration is found more sensitive to the model perturbations than the loop-loop configuration.1-D inversion of synthetic 1-D data sets for the wire-wire configuration finds resolution and estimation errors to be less than 10 percent for all the model parameters. For 3-D models, 1-D inversion results give a resolution error of 10 percent or less for the depth to, resistivity and thickness of, the 3-D inclusion. The estimate is within 10 percent of the true value for the first parameter but 40 percent for the other two. Resolution as well as estimation of the basement resistivity is always very poor.Using the wire-wire configuration, it is theoretically possible to define a buried resistive layer and any lateral change in its resistivity, subject to the above limitations of 1-D inversion. However, the basement resistivity cannot be estimated with reasonable accuracy in the presence of a lateral inhomogeneity in the overlying layer.     

中国西北空中可降水量的年内非均匀性特征

利用NCAR/NCEP资料,通过引进表征时间分配特征的参数集中度和集中期对西北上空大气可降水量年内非均匀性特征进行分析,结果表明:一致性异常分布是西北上空大气可降水量集中度和集中期的最主要的空间分布特征;西北地区上空大气可降水量集中度和集中期近45年来主要表现为2~4年、6~8年的高频振荡;西北上空大气可降水量集中度异常强弱年其水汽输送特征存在显著差异,在集中度异常强年,西北东南部西南季风水汽输送较常年偏强,其余区域西风带水汽输送较常年偏强,由于充足的水汽供应使得整个西北地区上空大气可降水量与常年相比偏多;反之亦然。