Stratospheric wave activity and the Pacific Decadal Oscillation

Using the monthly mean NCEP/NCAR reanalysis and NOAA Extended Reconstructed sea surface temperature (SST) datasets, strong correlations between the SST anomalies in the North Pacific and calculated three-dimensional Eliassen–Palm vertical fluxes are indicated in December 1958–1976 and 1992–2006. These correlations between the interannual variations of the SST anomalies and the penetration of planetary waves into the stratosphere are much less during the decadal sub-period 1976–1992 in the positive phase of the Pacific Decadal Oscillation (PDO) and the decadal cold SST anomalies in the North Pacific. Interannual variations of the polar jet in the lower stratosphere in January are strongly associated with SST anomalies in the Aleutian Low region in December for the years with positive PDO index. This sub-period corresponds well with that of the violation of the Holton–Tan relationship between the equatorial Quasi-Beinnial Oscillation (QBO) and the stratospheric circulation in the extra-tropics. It is shown that interannual and interdecadal variations of stratospheric dynamics, including stratospheric warming occurrences in January, depend strongly on changes of the upward propagation of planetary waves from the troposphere to the stratosphere over North Eurasia in preceding December. These findings give evidences of a large impact of the decadal SST variations in the North Pacific on wave activity in early winter due to changes of thermal excitation of planetary waves during distinct decadal periods. Possible causes of the decadal violation of the Holton–Tan relationship, its relation to the PDO and an influence of the 11-year solar cycle on the stratosphere are discussed.     

层间错动带的强度参数取值探讨

为获得高应力下具有剪切错动历史、延展规模大、组合结构和矿物构成多元化等特点的白鹤滩层间错动带强度值（黏聚力和内摩擦角）,首先介绍了6种错动带试验研究,包括针对错动带泥化软层的环剪试验、高压直剪试验和三轴压缩试验,以及针对错动带复合体的直剪试验、三轴压缩试验和现场试验。综合分析不同试验对象和不同试验条件下获得的错动带强度值,归纳出了错动带黏聚力和内摩擦角与试验方式、加载的法向应力大小、试样特点及含水率之间的关系,并发现白鹤滩错动带强度特性具有典型的组合体结构效应、弱胶结效应、围压效应、水软化效应。在此基础上,提出“原状错动带强度”和“扰动错动带强度”两个概念,并进一步讨论了白鹤滩厂址区原状的和扰动的层间错动带强度参数取值问题。其研究结果可为白鹤滩地下洞室群的安全设计和深部地下工程中同类泥化夹层的力学参数取值提供参考     

华北克拉通北缘及邻区印支期岩浆活动与钼和金成矿作用

对华北克拉通北缘及邻区19处钼矿床和5处金矿床的产出环境、形成时代和成矿机理及其与印支期侵入岩的关系进行了讨论。尽管各个矿床所处的地理位置不同,但是它们大都在前寒武纪或早古生代地层中产出,并且与印支期侵入岩具有密切的时空分布关系。印支期钼矿床的形成作用可以从早三叠世一直持续到晚三叠世,大规模成矿作用高峰期为230~220 Ma。相比之下,金矿床的形成时间明显早于钼矿床,同位素年龄数据集中分布在245~239 Ma。研究结果表明,自早三叠世开始,华北克拉通北缘及邻区曾发生过多期大规模伸展构造作用,并且形成若干条近东西向展布的裂陷带。张裂构造作用所诱发的富碱性岩浆作用及相关流体活动为钼或金矿床的形成提供了动力和物质来源,因此,印支期侵入岩发育区是寻找隐伏钼或金矿床的有利地区。     

渗透系数作为岩体卸荷分带量化指标的研究

渗透系数在一定程度上可以反映岩体内部裂隙发育程度、节理开度及卸荷程度,因此常作为岩体卸荷带划分的定量指标之一。但由于卸荷岩体的非线性特征,以及卸荷带研究方法和工程背景条件等方面的差异,各家划分卸荷带时所采用的渗透系数界限标准各有不同。本文从工程实例出发,通过对定性划分的各卸荷分带内对应钻孔段渗透系数的统计分析,以其统计平均值作为岩体卸荷分带的界线标准。实际应用表明,渗透系数作为卸荷带划分依据具有一定的优势,按渗透系数划分的卸荷带深度与其他方法综合确定的卸荷带深度基本接近。     

拓扑模型下的导航地图道路曲率引入

随着道路曲率的作用逐渐被认识,道路曲率引入导航地图,成为实现先进驾驶辅助系统(ADAS)的重要途径,也是未来导航地图的发展趋势之一。曲率依附于曲线存在,难以直接引入基于拓扑模型的导航地图。为了避免模型转换带来的巨大工作量和不确定性,本文尝试了拓扑模型下道路曲率引入的研究。首先在现有导航地图道路数据基础上,使用了完全曲线拟合与组合线型拟合两种方法计算曲率;然后结合两种计算方法对应的曲率存在形式,探索了在拓扑模型下的道路曲率引入方式,分别是引入点、引入线和引入多线;最后使用导航地图道路数据进行曲率计算和曲率引入的试验。结果表明,本文的方法具有可行性,为今后大数据量的导航地图道路曲率引入打下了铺垫。     

天津地区台基背景噪声特征分析

利用Welch算法,选取天津数字地震台网31个台站记录资料中不同时段的无震记录,对无震观测资料进行功率谱计算,然后进行统计分析,得出了天津地区的背景噪声特征:就季节而言,背景噪声值的高值出现在夏天和秋天,低值出现在春天和冬天;就时间而言,高值出现在白天的14时,低值出现在夜间的2时。对比噪声功率谱曲线发现,在0.125~1 Hz频段内有一个明显的峰值,这主要是受海洋的影响。在1~20 Hz频段内,天津地区的背景噪声值高值区出现在中心城区、静海、滨海新区,低值区出现在蓟县、宝坻、宁河、武清,且中心城区、静海、滨海新区白天时段的背景噪声值明显高于夜间时段,这主要是受人为噪声的影响,而在0.125~1 Hz频段内,天津所有地区差异不大。     

利用地震P波方位/角度信息预测煤层裂隙发育——以阳泉矿区为例

查明煤层瓦斯富集区域,对可能的瓦斯突出点进行预报,是当前煤矿生产中亟待解决的重要课题.利用地震P波对裂缝性地层所表现出的方位各向异性特征和AV0特征,应用地震P波方位/角度信息评价煤层裂隙发育带.通过对阳泉新景煤矿三维地震资料的处理,获得4个方位的偏移数据体和8个方位/角度的偏移数据体,从中提取了3种对煤层裂隙响应灵敏的地震属性,综合利用3种地震属性计算出裂隙的发育密度.预测结果表明,利用P波方位/角度信息比仅利用P波方位信息评价煤层裂隙发育带更具有优势,它能同时利用煤层反射波的各向异性特征和AVO特征,更有利于进行煤层的岩性解释.     

Petrogenesis of diabase from accretionary prism in the southern Qiangtang terrane,central Tibet: Evidence from U–Pb geochronology,petrochemistry and Sr–Nd–Hf–O isotope characteristics

The Bangong–Nujiang suture (BNS) between the Lhasa and Qiangtang terranes is an important boundary and its petrogenesis is controversial. Diabase from the accretionary prism in the southern Qiangtang terrane yields a zircon U–Pb age of 181.3 ± 1.4 Ma. All the diabases show tholeiitic basalt compositions, gentle enrichment patters of light rare earth elements (REE), variable enrichment in incompatible element concentrations (e.g. Th and Rb), and no anomaly in high field strength elements (e.g. Nb and Ta), similar to that of enriched mid‐ocean ridge basalt (E‐MORB). They have relatively homogeneous whole rock Nd (εNd(t) = 7.3–9.1) and zircon Hf–O isotopic compositions (εHf(t) = 14.8–16.1, and δ¹⁸O = 4.57–6.12‰), possibly indicating melting of the depleted mantle and no significant crustal contamination during the petrogenesis. The element variations suggest that the diabases were formed by plume–ridge interaction at a mid‐ocean ridge within the Bangong–Nujiang ocean.     

Time-domain solution for transient dynamic response of a large-diameter thin-walled pipe pile

The propagation of stress waves in a large-diameter pipe pile for low strain dynamic testing cannot be explained properly by traditional 1D wave theories. A new computational model is established to obtain a wave equation that can describe the dynamic response of a large-diameter thin-walled pipe pile to a transient point load during a low strain integrity test. An analytical solution in the time domain is deduced using the separation of variables and variation of constant methods. The validity of this new solution is verifi ed by an existing analytical solution under free boundary conditions. The results of this time domain solution are also compared with the results of a frequency domain solution and fi eld test data. The comparisons indicate that the new solution agrees well with the results of previous solutions. Parametric studies using the new solution with reference to a case study are also carried out. The results show that the mode number affects the accuracy of the dynamic response. A mode number greater than 10 is required to enable the calculated dynamic responses to be independent of the mode number. The dynamic response is also greatly affected by soil properties. The larger the side resistance, the smaller the displacement response and the smaller the refl ected velocity wave crest. The displacement increases as the stress waves propagate along the pile when the pile shaft is free. The incident waves of displacement and velocity responses of the pile are not the same among different points in the circumferential direction on the pile top. However, the arrival time and peak value of the pile tip refl ected waves are almost the same among different points on the pile top.