南海东北部陆坡与恒春海脊天然气水合物分布的地震反射对比

经过对"探宝号"调查船在2001年8月在南海东北部陆坡及台湾南部恒春海脊海域采集的多道地震剖面资料进行的地震反射波数据分析、研究和解释,结果表明:(1)南海东北部陆坡段区域和台湾南部恒春海脊海域地震剖面上均显示有被作为天然气水合物存在标志的BSR,但两区域构造成因、形式和相关地质环境的不同造成了此两处的天然气水合物成因及过程的不同.(2)南海东北部陆坡区域的水合物形成与该区广泛发育的断裂带、滑塌构造体及其所形成的压力场屏蔽环境有关,而台湾南部恒春海脊海域的天然气水合物的形成则与马尼拉海沟俯冲带相关的逆冲推覆构造、增生楔等及其所对应的海底流体疏导体系有关.(3)南海陆缘区域广泛发育有各种断裂带、滑塌构造体、泥底辟、俯冲带、增生楔等,且温压环境合适,是天然气水合物矿藏极有可能广泛分布的区域.     

武夷地块中南平-宁化构造带南华纪弧火山岩属性及其对华夏板块多微地体拼合的启示

武夷地块中各地体的活动解析是认识华夏板块构造活动演化的窗口。南平-宁化构造带作为划分南武夷地体和北武夷地体的重要边界活动带,其构造属性对我们认识武夷地块中南、北武夷地体的构造演化具有重要意义。前人对南平-宁化构造带中变质火山岩类的研究和认识存在争议,限制了我们对南平-宁化构造带的构造属性的理解。因此,本文利用野外路线地质调查、年代学测定、同位素地球化学测试等手段,对该套变质火山岩做了重点研究,结合前人的研究成果,我们得到以下认识:南平-宁化构造带中的变质火山岩类主要形成于756～720 Ma,主要形成于活动大陆边缘或岛弧环境,表明南平-宁化构造带可能代表了南武夷地体和北武夷地体之间的一条南华纪的近东西向的岛弧火山活动带,结合带中构造变形反映的南北向对冲的汇聚极性,我们认为南武夷地体和北武夷地体之间在南华纪可能还存在洋-陆碰撞乃至陆-陆拼合过程,这也反映了多微地块、多期拼合过程可能更符合华夏板块大地构造演化的主旋律。     

鄂尔多斯块体北缘Pn波层析成像研究

基于鄂尔多斯块体北缘2008～2018年台网数字化波形记录,利用Pn波层析成像技术获得研究区高精度的上地幔速度结构与各向异性。结果表明,研究区上地幔顶部Pn波速度存在明显的横向不均匀性,且与研究区构造活动及地震分布密切相关;河套断陷带各向异性快波方向呈近EW向。研究区多数历史强震发生在低速异常区或高低速异常过渡带上,该结果为理解研究区地震发生的相关性提供了新的地震学依据。     

Size distribution of urban blocks in the Tokyo Metropolitan Region: estimation by urban block density and road width on the basis of normative plane tessellation

The size distribution of urban blocks is important for the characterisation of urban block patterns and is known to follow several parametric statistical distributions. However, it has not previously been analysed on the basis of a normative plane tessellation and in terms of urban block density and mean road width. In this article, we formulate the size distribution of Voronoi cells using the gamma distribution estimated by urban block density and mean road width. We found that (1) both log-normal and gamma distributions can be good candidates for the size distribution of urban blocks at the scale of a region that consists of regular urban blocks and that has a uniform road width; and (2) the size distribution of urban blocks depends on the balance between pattern and width improvement effects. Based on one study region in Tokyo, if the pattern improvement effect is more prominent than the width improvement effect, the mode of urban block sizes tends to be larger than if it is not. These findings are expected to provide scientific support for urban planning (e.g. land readjustment projects).     

扬子地块东南缘多期构造变形及其油气意义

扬子地块的构造演化及其动力学机制约束着古生代海相油气成藏,而扬子地块东南缘的构造变形特征是理解整个扬子地块构造变形的关键所在.通过对武夷、云开和肇庆地区的构造特征研究,初步划分出扬子地块东南缘的三期重要变形①早古生代末期云开地区NW向剪切变形,武夷山地区ESE向剪切变形;②中生代早期云开、肇庆地区NE向逆冲推覆作用;③中生代晚期武夷山地区的脆性构造变形.在重新认识区内构造演化的基础上,对其动力学作了初步探讨.这些认识有助于今后中国南方碳酸盐岩含油气远景的评价.     

Vendian stage in formation of the Early Caledonian superterrane in Central Asia

Granitoids and metamorphic rocks of the Baidarik basement block of the Dzabkhan microcontinent are studied in terms of geology, geochronology (U-Pb dating of zircon microfractions and individual grains) and Nd isotopic-geochemical systematics. As is established, the formation history of metamorphic belt (disthene-sillimanite facies) in junction zone of the Baidarik block and Bayankhongor zone of the Late Riphean (～665 Ma) ophiolite association characterizes development of the Vendian (～560–570 Ma) active continental margin. The high-P metamorphic rocks of that time span evidence formation of structures with the Earth’s crust of considerable thickness. In Central Asia, events of the Vendian low-gradient metamorphism are established also in the Tuva-Mongolian massif, Kan block of the East Sayan Mountains, and South Chuya inlier of the Caledonides in the Altai Mountains. Based on these data, it is possible to distinguish the Late Baikalian stage in development of the Early Caledonian superterrane of Central Asia, which antedated the subsequent evolution of this structure during the Late Cambrian-Ordovician. The high-gradient metamorphism that affected most intensively the southeastern part of the Baidarik block can be correlated with the Early Paleozoic (525–540 Ma) evolution of active continental margin and associated development of the Vendian oceanic basins and island arcs of the Ozernaya zone.     

Removal of selected metals from drinking water using modified powdered block carbon

This paper presents the possible alternative removal options for the development of safe drinking water supply in the trace elements affected areas. Arsenic and chromium are two of the most toxic pollutants, introduced into natural waters from a variety of sources and causes various adverse effects on living bodies. Performance of three filter bed method was evaluated in the laboratory. Experiments have been conducted to investigate the sorption of arsenic and chromium on carbon steel and removal of trace elements from drinking water with a household filtration process. The affinity of the arsenic and chromium species for Fe/Fe₃C (iron/iron carbide) sites is the key factor controlling the removal of the elements. The method is based on the use of powdered block carbon (PBC), powder carbon steel and ball ceramic in the ion-sorption columns as a cleaning process. The PBC modified is a satisfactory and practical sorbent for trace elements (arsenite and chromate) dissolved in water.     

GNSS辅助摄影测量中几个问题的探讨

GNSS辅助摄影测量是在数字摄影测量基础上发展起来的一种技术手段。它使航空摄影、像片控制点布设、外方位元素的获取和空中三角测量进入了一个新时代。本文对航摄分区和补摄、区域划分以及像控点布设应注意的问题进行了探讨,同时,对应用前景进行了概述。     

Exploring the performance of spatio-temporal assimilation in an urban cellular automata model

Urban cellular automata (CA) models propagate and accumulate errors during the modeling process due to the model structure or stochastic processes involved. It is feasible to assimilate real-time observations into an urban CA model to reduce model uncertainties. However, the assimilation performance is sensitive to the spatio-temporal units in the assimilation algorithm, that is, spatial block size and window length (temporal interval). In this study, we coupled an assimilation model, an ensemble Kalman filter (EnKF) and a Logistic-CA model to simulate the urban dynamic in Beijing over a period of two decades. Our results indicate that the coupled EnKF-CA model outperforms the CA-alone counterpart by about 10% in terms of the figure of merit, which reflects the agreement of modeled pixels. We also find that the assimilation performance using a finer block (1 km) is better than that using a coarser block (5 km and 10 km) because of the better depiction of spatial heterogeneity using a finer block. Moreover, the improvement of intermediate outputs using the coupled EnKF-CA model is effective for a certain period (e.g. 5 years). This implies that a high-frequency assimilation may not significantly improve the model performance. The sensitivity analyses of spatio-temporal assimilation in the EnKF-CA model provide a better understanding of the assimilation mechanism that couples with land-use change models.     

应用GPS建立航测区域控制网的设计与实践

介绍了应用GPS建立西安市1:500航测数字化成图的区域控制网的设计方案、外业施测、数据检核与数据处理的方法与经验.