华北北部地区地下水10年准周期及其与地震活动关系分析

1966年以来华北北部发生5．0级以上地震16次,根据时间上的密集程度可分为5个地震丛。地下水资料经过排出地下水超采造成的趋势下降干扰后,多井地下水资料呈现出10年准周期变化的同步性特征。地震丛发生在地下水多年周期的高值段,低值年份则没有中强以上地震发生。将10年准周期按一定规则分成低值段、上升段、高值段和下降段,在地下水10年周期4个时段的发震概率分别为0％、25％、50％、25％。     

台湾与长-南地震带中强地震活动的周期性与相关性研究

依据板块运动的学说,在分析台湾与长-南(长江中下游-南黄海,下同)地震带地质构造内在联系的基础上,运用极值理论对1970年至2005年间台湾和长-南地震带的地震分别进行统计研究。得出了相应震级地震的复发周期T(M)和发震概率(P)及其概率阈值(Po)。通过对T(M)的同比分析,发现两地中强地震存在着较好的相关性。用以上研究结果对长-南地震带5级以上地震的危险性、发震时间和地震强度进行了综合判定,收到了较好的预报效能。     

Derivation and relative performance of strings of line elements for modeling (un)confined and semi-confined flow

In the analytic element method, strings of line-sinks may be used to model streams and strings of line-doublets may be used to model impermeable walls or boundaries of inhomogeneities. The resulting solutions are analytic, but the boundary conditions are met approximately. Equations for line elements may be derived in two ways: through integration of point elements (the integral solution) and through application of separation of variables in elliptical coordinates (the elliptical solution). Using both approaches, two sets of line elements are presented for four flow problems: line-sinks and line-doublets in (un)confined flow, and line-sinks and line-doublets in semi-confined flow. Elliptical line elements have the advantage that they do not need a far-field expansion for accurate evaluation far away from the element. The derivation of elliptical line elements is new and applicable to both (un)confined flow and semi-confined flow; only the resulting expressions for elliptical line elements for semi-confined flow have not been found in the current groundwater literature. Existing solutions for elliptical line elements for (un)confined flow were intended for the modeling of isolated features. Four examples are presented, one for each flow problem, to demonstrate that strings of elliptical line elements may be used to obtain accurate solutions; elliptical line-doublets for semi-confined flow can only be strung together in combination with two integral line-doublets. For a zigzag canal in (un)confined flow, a string of elliptical line-sinks performed better than a string of integral line-sinks of the same order when the smallest angle between two adjacent segments is less than 130°. Elliptical line-doublets performed better than integral line-doublets for a square inhomogeneity in a uniform, confined flow field; the difference was smaller for an octagonal inhomogeneity. For semi-confined flow, the difference between the integral and elliptical line-sinks was small when modeling a zigzag canal.     

A stochastic model for initial movement of sand grains by wind

A stochastic model for entrainment of sand grains by wind is presented through analysis of the forces exerted on a single spherical grain, coupled with fluctuations of wind velocity and the change in grain position on the surface. The structure of the stochastic model is consistent with experimental data in the literature. The probability of initial motion increases first, and then decreases, with grain size. It reaches a maximum at diameters of about 0·9 mm. Some sand grains are still in motion at less than the conventional threshold velocity, even at very low velocities. The probability of sand grain movement reaches unity at twice the conventional threshold velocity. Considerable discrepancies amongst conventional threshold formulae may result from the different probabilities of initial movement implied in these formulae. Copyright © 2008 John Wiley & Sons, Ltd.     

岩体不连续面迹长与直径间的概率关系模型分析

由于“随机”概念的模糊性,在假定不连续面为薄圆盘及弦长作为迹长的前提下,基于迹线端点在圆周上均匀分布、迹线中点在直径上均匀分布、迹线中点在圆面域内均匀分布这3种明确而又不同的“随机”含义,可以得到3种合理的迹长 与直径 间的概率关系模型。通过对这3种模型进行分析认为：其在各自的“随机”含义下都是正确的,只是适用条件各异;野外实际可行的条件是介于模型2 和模型3之间的,合理地分析应该同时考虑这两种模型。在实际应用中,应该首先对所有取样面产状之间的关系进行分析,根据其结果来分配给模型2和模型3以某种权重,这样得到的迹长与不连续面直径之间概率关系更具合理性,其结果弥补了目前国内外进行的相关研究仅仅考虑到第2类模型的不足。     

异地海域年极值风暴增水同现规律的探讨

以塘沽和龙口海洋观测站20年极值增水值为样本，基于二维冈贝尔逻辑分布模式，探讨了不同海域风暴潮增水极值的联合分布规律。通过对二维分布的联合概率密度、条件概率密度和同现概率的计算，给出了相应的工程设计参数，供有关部门在防潮规划时参考。     

Prediction of Extreme Sea-State Encountered by Oceangoing Vessels

In order to determine the extreme sea-state encountered by oceangoing vessels,a method forthe prediction of wave parameters based on the data of long-term distribution sample is developed by useof the fitting approach with the Weibull probability functions and the power functions.As an example aspecial calculation result is given including the analysis of wave parameters for the data of the NorthAtlantic Basin and the computation of motion and load encountered by two container ships CSLR andCSBV in different loading conditions.All computation results are satisfactory compared with corre-sponding design results.     

基于实测资料的畸形波概率及波浪要素分析

根据Kjeldsen对畸形波的定义：波高大于有效波高的2倍（H/H_1/3＞2）,基于实测波浪资料,统计分析了江苏射阳海域和广东南澳海域的畸形波个数和波浪要素。江苏射阳海域畸形波发生概率为0.005 7%,广东南澳海域畸形波发生概率为0.007%。用Rayleigh分布、双参数Weibull 分布和MER分布对实测数据得到的特征波高进行了拟合,研究了海域内畸形波发生的概率分布。拟合结果表明：MER分布更适合描述两个海域畸形波的发生概率,两个海域畸形波的发生概率均高于Rayleigh分布和Weibull分布。在测量数据期间,台风在海域过境可能增加畸形波的发生概率;同时两个海域的双峰谱占比为22.7%和5.8%,可能也是导致畸形波发生概率增加的原因之一。     

西江水文干旱历时与强度的遭遇概率分析

利用西江下游马口水文站1959 2009年月径流量数据计算径流干旱指数,经游程理论提取了水文干旱特征值.应用Copula函数分析水文干旱强度和历时之间的联合概率分布.对构建的干旱历时和强度联合分布模式进行分析,结果表明:(1)径流干旱历时和强度之间具有高关联性,秩相关系数达0.617;(2)三参数Weibull分布较好地描述了干旱历时和强度的边缘分布特征;(3)经拟合优度检验结果优选的干旱历时和强度之间的较优连接函数为Archimedean类的Gumbel-Hougaard Copula函数;(4)5～10年重现期和20年重现期的水文干旱分别达到了重旱级别和特旱级别;(5)干旱历时和强度之间的遭遇概率可为特定干旱历时与水文干旱级别或特定干旱强度与干旱历时之间的对应关系提供概率意义上的干旱特征诊断与预测.     

山东某场地概率地震危险性分析

利用概率地震危险性分析(CPSHA)方法,对山东某场地进行地震危险性分析,通过对该场地划分潜在震源区,确定地震活动性参数及地震动衰减关系,计算分析地震危险性概率,基本确定对该场地地震动峰值加速度起主要贡献的几个潜在震源区及贡献值,并确定该场地50年超越概率10%的水平向基岩地震动加速度峰值。结果发现,CPSHA方法以具体的构造尺度和更加细致的构造标志来划分潜在震源区,使潜在震源区规模缩减,从而更能反映地震活动在空间分布上的不均匀性。