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881.
Tan K. Wang Ben Jhong Yang Jia-Ming Deng Chao-Shing Lee Char-Shine Liu 《Marine Geophysical Researches》2010,31(1-2):59-76
Horizon velocity analysis and pre-stack depth migration of seismic profiles collected by R/V Maurice Ewing in 1995 across the accretionary prism off SW Taiwan and along the continental slope of the northernmost South China Sea were implemented for identifying gas hydrates. Similarly, a survey of 32 ocean-bottom seismometers (OBS), with a spacing of about 500 m, was conducted for exploring gas hydrates on the accretionary prism off SW Taiwan in April 2006. Travel times of head wave, refraction, reflection and converted shear wave identified from the hydrophone, vertical and horizontal components of these OBS data were applied for imaging P-wave velocity and Poisson’s ratio of hydrate-bearing sediments. In the accretionary prism off SW Taiwan, we found hydrate-bearing sediment, with a thickness of about 100–200 m, a relatively high P-wave velocity of 1.87–2.04 km/s and a relatively low Poisson’s ratio of 0.445–0.455, below anticlinal ridges near imbricate emergent thrusts in the drainage system of the Penghu and Kaoping Canyons. Free-gas layer, with a thickness of about 30–120 m, a relatively low P-wave velocity of 1.4–1.8 km/s and a relatively high Poisson’s ratio (0.47–0.48), was also observed below most of the bottom-simulating reflectors (BSR). Subsequently, based on rock physics of the three-phase effective medium, we evaluated the hydrate saturation of about 12–30% and the free-gas saturation of about 1–4%. The highest saturation (30% and 4%) of gas hydrates is found below anticlines due to N–S trending thrust-bounded folds and NE-SW thrusting and strike-slip ramps in the lower slope of the accretionary prism. We suggest that fluid may have migrated through the relay-fault array due to decollement folding and gas hydrates have been trapped in anticlines formed by the basement rises along the thrust faults. In contrast, in the rifted continental margin of the northernmost South China Sea, P-wave velocities of 1.9–2.2 km/s and 1.3–1.6 km/s, and thicknesses of about 50–200 m and 100–200 m, respectively, for a hydrate layer and a free-gas layer were imaged below the remnant and erosional ridges in the upper continental slope. High P-wave velocity of hydrate-bearing sediment below erosional ridges may also indicate high saturation of hydrates there. Normal faults due to rifting in the South China continental crust may have provided conduits for gas migration below the erosional ridges where P-wave velocity of hydrate-bearing sediment in the passive continental margin of the northernmost South China Sea is greater than that in the active accretionary prism off SW Taiwan. 相似文献
882.
883.
多尺度分析方法实现了信号分析的时频局部化,是测井数据时频分析与地质解释恰当的数学工具.测井资料作为地层岩性、物性的反映,其中必然蕴含了大量与沉积地层旋回变化有关的信息.以胜坨油田某井为例,采用db4最佳小波基分别对自然伽马、自然电位和声波等测井曲线进行了多尺度分析,将一维测井数据拓展为二维深度-尺度空间,提取小波变换系数的时频色谱信息和能量信息,从而确定出测井曲线识别准层序界面的最佳尺度.依据最佳尺度下的小波系数幅度振荡特征和时频色谱信息实现了对准层序界面的自动划分,与传统方法所划分的界面基本一致.这些探索为层序地层的定量划分提供了一种新的思路. 相似文献
884.
关注生态系统服务价值(Ecosystem service value,ESV)与城市化耦合协调互动关系,对黄河流域高质量发展大有裨益。文章运用熵权法、耦合协调模型、空间自相关模型,障碍度模型分析了城市化与ESV的耦合协调关系及主导障碍因素。结果表明:(1)1995—2018年,黄河流域ESV发生了很大的改善,整体增加了33.05×109元,且以调节服务为主导,草地、林地、耕地服务价值对总ESV贡献率较高。单位面积生态系统服务价值(PE)呈现南高北低、中游高上下游低的空间格局。(2)PE与城市化耦合协调度(Coupling coordination degree,CCD)逐渐改善,轻度耦合协调增加了27.12%,严重失调类型减少了45.46%,耦合亚型从城市化滞后型转变为ESV滞后型;从空间上看,CCD呈现南高北低、中游优于上游和下游的空间格局,协调度具有显著的空间正相关性,存在明显的高-高和低-低集聚特征,高-高集聚区主要分布在ESV高且城市化水平相对较高的中游和下游地区,低-低集聚区主要分布在ESV较低的上游地区。(3)1995—2018年主导障碍因素未发生明显... 相似文献
885.
谭术魁 《中国地理科学(英文版)》1999,9(1):1-11
Duringthefloodperiodof1998,someregionsofChinasufferedseriousfloodingandwaterlogging.EspeciallyintheChangjiangRiver,thewholebasinfloodonceemergedin1954occurredagain,andthemostseverefloodinthehistoryalsoemergedintheSonghuaRiverandtheNenjiangRiver,whicharousedmuchattentionacrossthewholecountry.Accordingtoincompletestatistics,till22ndofAugust,29provinces,autonomousregionsandmunicipalitieshadbeenaffectedbythefloodsinvaryingdegrees.ZI.2millionhaoflandwereinundated,223millionPeOPlewereaffeCted,3… 相似文献
886.
887.
As a hot topic in Landscape Ecology study, ecological connectivity is an important indicator for regional land sustainable use and biological protection. This paper conducted a systematic assessment of ecological connectivity using remote sensing images of Dongshan Island in 1994, 2003 and 2011. Based on least-cost modelling, the method takes into consideration the type of barrier, the distance impact, and the adjacent land use types to obtain the Barrier Effect Index (BEI) and Ecological Connectivity Index (ECI). The application of this method to Dongshan Island showed the ecological connectivity index (ECI) was low in 1994, improved in 2003, and decreased significantly in 2011. The results of the dynamic analysis of landscape structure showed farmland and roads were the main landscape classes that caused the low observed ECI in 1994 and 2003; these tended to divide the landscape and cause fragmentation. Construction land and roads were the main landscape classes resulting in low ECI in 2011, while forest and grassland had a high ECI. Trajectory analysis showed ECI tended to decrease in the low mountain forest zone of the northwestern and southeastern parts of Dongshan Island as well as in the coastal protection forest area. The areas where ECI became high were located in the northeastern part of Dongshan Island where cities and towns are concentrated with high human populations. Therefore, rapid urbanization has been the most important factor driving changes in landscape structure and patterns during the last 17 years on Dongshan Island. The approach not only assists us in revealing the driving mechanism of landscape dynamics from another aspect, but also can assess the impacts of regional and urban plans on landscape structure and function. 相似文献
888.
?????й?????????????缰?????沿??GNSS???????и????????????GPS???????????????忦?????????????????????????????????????????????????????????????????????? 相似文献
889.
An experiment was performed to determine the dietary phosphorus requirement of the young abalone,Haliotis discus hannai. Five semi-purified diets were formulated to provide a series of graded levels of dietary total phosphorus (0.23%–1.98) from
monobasic potassium phosphate (KH2P04). The brown alga,Laminaria japonica, was used as a control diet. Similar size abalone were distributed in a single-pass, flow-through system using a completely
randomized design with six treatments and three replicates each treatment. The abalone were hand-fed to satiation with appropriate
diets in excess, once daily at 17:00. The feeding trial was run for 120-d. Survival rate and soft-body to shell ratio (SB/S)
were constantly maintained regardless of dietary treatment. However, the weight gain rate (WGR), daily increment in shell
length (DISL), muscle RNA to DNA ratio (RNA/DNA), carcass levels of lipid and protein, soft-body alkaline phosphatase (SBAKP),
and phosphorus concentrations of whole body (WB) and soft body (SB) were significantly (ANOVA, P<0.05) affected by the dietary
phosphorus level. The dietary phosphorus requirements of the abalone were evaluated from the WGR, DISL, and RNA/DNA ratio
respectively, by using second-order polynomial regression analysis. Based on these criteria, about 1.0%–1.2% total dietary
phosphorus, i.e. 0.9%–1.1% dietary available phosphorus is recommended for the maximum growth of the abalone.
Project 39670572 supported by the NSFC. 相似文献
890.
我国土壤中结合态硒的含量和分布规律 总被引:18,自引:3,他引:15
本文提出并建立了Jackson法系统分离土壤中不同形态硒的实验程序,研究了我国几种土壤表层(0—20cm)中硒的结合形态及其地理分布规律,并对植物可利用性作了评价。 相似文献