Comparison of non-Gaussian multicomponent and periodic autoregressive models for river flow

The Non-Gaussian Multicomponent model for river flow (NGM) of Vandewiele and Dom is modified in order to facilitate maximum likelihood estimation. It is also generalized so that a wider variety of river flows at a diversity of time steps can be modeled. This model is applied to two basins in Belgium and France with very different areas, both at monthly and weekly time scale. Results on the quality of forecasting and simulation (especially simulation of low and high flow volumes) are compared with those of classical Periodic Autoregressive models (PAR). Results with NGM are always better, in most cases considerably better. This is due to the fact that NGM models explicitly take into consideration the presence of so called flow components, like baseflow and direct flow recession, which are phenomena well known to hydrologists.     

岩石突发失稳序列的实验研究

根据三轴压缩条件下岩石试件变形过程中多次重复发生的粘滑失稳事件，着重研究了突发失稳序列的演变特征及其影响因素。研究表明，随着错动量的增大，突发失稳的临界差应力和应力降呈现“正坡”、“负坡”和“平缓跳动”等阶段性变化，而应力降比率则渐趋减小；其变化原因主要与错动面的密接和凹凸程度、碎屑厚度、粒度、以及试件受力和刚度约束条件的改变等因素有关。突发失稳序列的变化特征，有可能为预测后续地震强弱变化的趋势提供依据     

大同－阳高两次地震的对比分析

１９８９年１０月，１９９１年３月，在山西北部大同盆地先后发生Ｍｓ６．１、Ｍｓ５．８两次中强地震。对比这两次地震的序列、空间分布及能量释放等存在很大差异。两次地震属同一地震序列，５．８级地震的活动规律具有晚期强余震的特点，是６．１级地震活动的一次大的起伏。进一步分析表明，大同—阳高的两次地震活动，以及在此期间山西地区发生的一系列５级左右地震活动，是华北地区区域应力场增强，较大范围内应力增加和传递的结果。     

华北地震区地震平静幕持续时间的变化及其解释

本文研究了华北地震区地震平静幕持续时间的变化。发现在每个地震活动期里地震平静幕的持续时间以非线性方式衰减。笔者用灰色系统ＧＭ（１，１）模型拟合了这一非线性特点并用流变体模型对这个特点作了初步解释。     

日本俯冲带应力产生与传播的数值模拟

用三维有限元模拟了日本地冲带，分析了板块推力、板块拉力、动态闭锁断层和解耦板间地震对上覆板块内部应力状态的贡献，表明大洋板块推力是海沟。岛弧地区挤压应力的主要来源，这种应力仅有小部分传播到上覆板块内部，软流圈的蠕变能促进这个应力传播过程使岛弧区的应力增大，由密度差异引起的板块拉力产生了分散的挤压应力和拉张应力。断层闭锁导致应力局部集中，板间地震的断层错动只对破裂附近小范围的应力状态产生影响     

华北北部地区主要断裂带的小构造和显微构造研究

利用计算机和电子显微镜对华北北部地区主要断裂带的构造节理和断层泥的测量、统计和研究，仅得到２０％左右的构造节理是处在有利于现代构造应力场易于活动的方位上。这些构造节理基本上是在与断裂带形成有关的局部构造应力条件下形成。ＳＥＭ显微构造研究得到了这些断裂带最近一次活动的相对年代和它们曾经历过的运动方式。这些方法的运用，对于断层活动性的研究起到拓宽视野的作用，并可提供更多的证据     

水库蓄水引起的附加应力场,孔压场和形变场

针对５种模拟库区：库心存在正断层；库心存在逆断层；库边存在正断层，水库蓄水在上盘；库边存在正断层，水库蓄水在下盘；库心存在带内由胶结程度更好的介质所填充的正断层，分别计算了水库蓄水引起的附加应力场、孔压场和形变场，并对它们的分布特征作了综合分析。     

Debris-fan constrictions and flood hydraulics in river canyons: Some implications from two-dimensional flow modelling

Rapids in river canyons are frequently found at sites where debris fans constrict flow along the channel. Whereas some fans may have persisted in the same location with unchanging geometry for centuries to millennia, others have changed in response to flow conditions imposed by successive floods. Such a change in boundary conditions may alter local flow hydraulics. This paper utilizes two-dimensional flow modelling to compare flood hydraulics along two alternative versions of an idealized reach of a river canyon: one with uniform width, gradient and cross-section, and a second perturbed by a prominent debris fan along the valley wall. The flow pattern along the reach with the fan is far more complex than the pattern along the uniform reach. Maximum velocity along the debris-fan reach is up to 50 per cent higher than along the uniform reach, maximum bed shear stress is up to three or four times higher, and an area of supercritical flow is predicted extending from the nose of the fan into the zone of flow expansion immediately downstream. Comparison of model output along longitudinal profiles of the two reaches indicates that the backwater effect of the fan extends several valley widths upstream. Predicted flows based on the same stage are as much as 190 to 230 per cent greater along the uniform reach than along the debris-fan reach. Reconstruction of palaeoflood discharge based on remnant flood marks in the vicinity of the fan would be sensitive to assumptions about boundary conditions that existed in the past; this effect relaxes over a longitudinal distance of several hundred metres. Furthermore there are significant cross-stream gradients that change slope and direction several times in the vicinity of the fan, calling into question the utility of one-dimensional step-backwater hydraulic models for predicting high-water marks in areas of complex valley morphology.     

Visualization of the turbulent flow structure in a gravel-bed river

A novel technique for visualizing turbulent flow data from a gravel-bed river is presented. The time development of flow velocity and shear stress at three heights is displayed using a computer program. This can be used to observe how the fluctuations of velocity and shear stress interact both spatially and temporally. We highlight examples of flow events which are important for the understanding of flow dynamics. The visualization suggests that the turbulent flow-field is characterized not only by coherence over time at a point, but also by spatial interdependence between points. We suggest that this new visualization approach will assist further interpretation of statistical analyses of turbulent signals, as well as focusing future measurement strategies by providing a clearer spatio-temporal picture of the flow structure.     

湄洲湾中央深槽及白牛浅滩的成因探讨

通过流场和地形特征的分析，研究湄洲湾中央深槽及白牛浅滩的形成机理。从湾顶延伸至口外的中央深槽，在半岛、岛屿和岬角控制下，由潮流塑造而成，但发育过程各段不尽相同，有涨潮流作用为主、落潮流作用为主和涨落潮流共同作用的三种类型。白牛浅滩的地貌形态，似沙嘴，如沙脊，又像独立的堆积体，形成模式与众不同，是湄洲湾中一个特殊的浅滩。