垂直重力梯度反演Moho面的频谱域公式及其应用

通过求解引力相等原则下的Fredholm积分方程,可以得到不规则单一密度界面(Moho面)的起伏.本文充分参考了前人的理论研究,推导出扰动垂直重力梯度确定Moho面深度的频谱域表达式,该式具有二次项迭代精度.运用此公式进行了全球Moho面的恢复计算,并将该结果与CRUST1.0模型和GEMMA Moho模型进行了对比和验证.     

不规则载荷影响地表近场垂向位移和倾斜观测的定量计算﹡

基于均匀的、各向同性的半无限弹性体的点状载荷模型引起周边垂向位移场变化的解析解,本文推导了水平倾斜场的解析解计算方法,给出了二维、三维不规则形状载荷对地面或地下某点的垂直位移和水平倾斜的解析解计算方法。并对比分析了质点简化模型和不规则模型的差异性。最后给出了据不规则形状载荷模型得到的近场垂直位移以及水平倾斜场的展布特征。研究结果表明,相对质点简化模型,不规则载荷模型对近场的刻画具有一定优势;二维不规则形状载荷模型的建立可将载荷散点化后将矢量叠加进行计算;三维不规则形状载荷模型在载荷散点化后,通过赋予散点的不同权重进行载荷重新分配,然后用矢量计算法获取位移场的变化;在二维和三维不规则载荷散点化后的矢量叠加过程中都存在着较明显的收敛过程,表明该计算方法的正确性和可行性。     

呼图壁地下储气库部分区域地表垂直形变机理研究

利用在呼图壁地下储气库开展的2013~2015年7期二等水准测量获得的高差数据,对受地表气井压力变化影响而发生的地下储气库地表垂直变形进行了分析。研究表明,呼图壁地下储气库区的地表变形除了构造成因引起的盆地下沉以外,其他成因有2个方面:一个是呼图壁地区的地下水超采影响着该地区的地表垂直变化;另一个是储气库集采气期间受井口压力变化影响的地表沉降,根据计算,储气库每MPa气井压力变化影响到的地表变化为0.625~1.125mm。     

一次西南涡暴雨的等熵位涡特征分析

应用常规资料和0.5°×0.5°的GFS再分析资料,对2010年7月19日发生在河北山东的一次西南涡暴雨过程产生的条件及其等熵位涡演变特征进行了分析。结果表明：西南涡、高、低空急流、地面低压是这次暴雨过程的主要影响系统;等熵位涡的演变和形态对冷空气活动有很好的示踪作用;等熵位涡中心两侧气流辐合,利于地面低压发展;高位涡下传,导致了大暴雨产生;等熵位涡大值区及移动方向与降水落区有很好的对应关系。     

利用小波分析研究河西地区地壳垂直形变特征

利用小波分析对河西地区1971—1979、1979—1983年的地壳垂直形变场进行计算,结果表明:三阶以内的小波分解结果与地质构造走向基本一致,说明河西地区地壳垂直运动的短波主要反应的是断层活动;四阶小波变换结果为地壳垂直形变的低频部分,反映的是大区域地质构造运动所引起的地壳垂直形变。1971—1979年,门源南部的地壳垂直运动相对剧烈,而到了1979—1983年,门源地区地壳垂直运动主要活动区域由门源南部地区转移到门源附近区域,这可能与门源6.4级地震孕育的区域构造活动有关。     

宁蒗5.7级地震前通海垂直摆倾斜异常变化分析

对通海地震台垂直摆倾斜仪观测资料在宁蒗5.7级地震前出现的异常进行了分析,结果表明通海台倾斜仪在震前出现明显的中期、短临异常,有明显的趋势转折、破年变、矢量反向、速率超二倍均方差等现象。     

基于无人机垂直观测的南京PM2.5污染个例研究

为了深入理解边界层内气温、相对湿度对PM2.5垂直分布和近地面污染的影响,本文使用搭载了多参数大气环境探测传感器的无人机对南京2017年12月3～4日和12月23～24日的PM2.5浓度、气温和相对湿度进行垂直观测,结合对气象数据的分析及HYSPLIT4（Hybrid Single Particle Lagrangian Integrated Trajectory version 4）轨迹计算模式的应用,对这两次PM2.5的垂直分布特征及污染过程的成因进行了分析。结果表明,PM2.5浓度和相对湿度呈明显的正相关关系,在12月23～24日的6次观测中相关系数均值达到0.96。逆温层下部,PM2.5浓度和相对湿度高且垂直差异较小;逆温层以上,PM2.5浓度和相对湿度随高度升高而迅速降低。由于大气扩散条件较差,导致PM2.5在华北平原南部不断累积,之后受到高压系统的影响分别向南和东南转移。这两次PM2.5污染过程都明显受到外部输送的影响,大气逆温对PM2.5和水汽的向上输送有明显的抑制作用,外部输送和局部逆温是导致这两次PM2.5污染的主要原因。     

Apatite fission-track analyses on basement granites from south-western Meseta, Morocco: Paleogeographic implications and interpretation of AFT age discrepancies

This work is based on apatite fission-track analysis of samples (mostly granites) from the basement of the Cretaceous-Tertiary Phosphate and Ganntour Plateaus, exposed in the Jebilet and Rehamna massifs (Western Meseta, Morocco). This basement belongs to the Carboniferous-Early Permian Variscan Belt, and the earlier marine onlap is Late Triassic in age. However, the AFT ages are post-Triassic and different in the Jebilet (186-203 Ma) and Rehamna (148-153 Ma). Track length modelling support the occurrence of moderate heating events during the Jurassic and the Eocene, respectively, with cooling during the Permian and Cretaceous intervals. These results are partly accounted for by considering a moderate subsidence during the Late Triassic-Liassic, which is a noticeable change in the regional paleogeographic concept of “West Moroccan Arch”. However, the discrepancies between the AFT results from the studied massifs make necessary to explore further explanation. We interpret the observed discrepancies by the difference in age and depth of crystallization of the sampled granites in the Variscan Orogen, i.e. 330 Ma, 5-6 km in the Jebilet versus ~ 300 Ma, 8-10 km in the Rehamna. The importance of the Late Jurassic-Early Cretaceous uplift and erosion of the entire Meseta and that of its Late Eocene burial are emphasized.     

Effect of local variations of vertical and horizontal stresses on the Cenozoic structuring of the mid-Norwegian shelf

The mid-Norwegian margin has a complex history and has experienced several phases of changing horizontal and vertical stresses on regional and local scale during the Cenozoic time. In addition to regional stresses related to the opening of the North Atlantic (i.e. ridge push), local variations in stress history may be important for development, distribution and reactivation of structures in the Vøring area in Cenozoic time. Presence and stability of flexural hinge zones between areas of relative uplift and subsidence have played an important role for focusing shallow horizontal stresses within the basins. Emplacement of lower crustal bodies during break-up will, whatever the nature of these bodies, have substantial isostatic effects, and modelling show that this could cause many hundred meters of temporal uplift above the lower crustal bodies, locally exceeding 1300 m of surface uplift. Effects of intra plate stress (IPS) are modelled along three 2D transects across the Vøring Basin. Modelling shows that IPS may have given substantial vertical motions in certain areas of the mid-Norwegian shelf, both with extensional IPS at the time of break-up, and later with compressive IPS during Tertiary time. The modelling assumes a strongly reduced effective elastic thickness (EET) due to lithospheric heating at break-up and later increasing EET as the lithosphere cooled towards present time. Our modelling takes into account the tectonic and isostatic effects of loading faulting and lithospheric thinning throughout the geological history, including several phases of extension prior to the Cenozoic compression. This approach emphasizes the importance of the deformation history of the lithosphere compared to other studies that only take into account the effects of Cenozoic processes of compression and loading on the sedimentary units. We do not state that isostatic uplift or intra plate stress are the most important causes for Cenozoic uplift and compressional deformation in this area, but point to the fact that these factors locally may have played an important role in focusing deformation caused by an interplay of different mechanisms.     

Flow dynamics inside the rotor of a three straight bladed cross-flow turbine

In this work we study experimentally the flow dynamics inside the rotor of a three straight-bladed Cross-Flow Turbine (CFT). The CFT model used in the experiments is based on symmetric NACA-0015 profiles, with a chord to rotor diameter ratio of 0.16. The turbine model was designed in order to quantify the flow inside and around the rotor using planar Digital Particle Image Velocimetry (DPIV). Tests were made by forcing the rotation of the turbine with a DC motor, which provided precise control of the Tip Speed Ratio (TSR), while being towed in a still-water tank at a constant turbine diameter Reynolds number of 6.1 × 10⁴. The range of TSRs covered in the experiments went from 0.7 to 2.3.The focus is given to the analysis of the blade-wake interactions inside the rotor. The investigation has allowed us to relate the interactions with the performance differences in this type of turbines, as a function of the operational tip speed ratio.