AVO analysis of BSR to assess free gas within fine-grained sediments in the Shenhu area,South China Sea

Gas hydrates have been identified from two-dimensional (2D) seismic data and logging data above bottom simulating reflector (BSR) during China’s first gas hydrate drilling expedition in 2007. The multichannel reflection seismic data were processed to be preserved amplitudes for quantitatively analyzing amplitude variation with offset (AVO) at BSRs. Low P-wave velocity anomaly below BSR, coinciding with high amplitude reflections in 2D seismic data, indicates the presence of free gas. The absolute values of reflection coefficient versus incidence angles for BSR range from 0 to 0.12 at different CMPs near Site SH2. According to logging data and gas hydrate saturations estimated from resistivity of Site SH2, P-wave velocities calculated from effective media theory (EMT) fit the measured sonic velocities well and we choose EMT to calculate elastic velocities for AVO. The rock-physics modeling and AVO analysis were combined to quantitatively assess free gas saturations and distribution by the reflection coefficients variation of the BSRs in Shenhu area, South China Sea. AVO estimation indicates that free gas saturations immediately beneath BSRs may be about 0.2 % (uniform distribution) and up to about 10 % (patchy distribution) at Site SH2.     

Estimation of the minimum food requirement using the respiration rate of medusa of Aurelia aurita in Sihwa Lake

We examined the respiration rate of Aurelia aurita medusae at 20 °C and 28 °C to evaluate minimum metabolic demands of medusae population in Sihwa Lake, Korea during summer. While weight specific respiration rates of medusae were constant and irrespective to the wet weight (8?C220 g), they significantly varied in respect to temperatures (p<0.001, 0.11±0.03 mg C g^?1 of medusa d^?1 at 20°C and 0.28±0.11 mg C g^?1 of medusa d^?1 at 28 °C in average, where Q ₁₀ value was 2.62). The respiration rate of medusae was defined as a function of temperature (T, °C) and body weight (W, g) according to the equation, R=0.13×2.62^(T-20)/10 W ^0.93. Population minimum food requirement (PMFR) was estimated from the respiration rate as 15.06 and 4.86 mg C m^?3 d^?1 in June and July, respectively. During this period, increase in bell diameter and wet weight was not significant (p=1 in the both), suggesting that the estimated PMFR closely represented the actual food consumption in the field. From July to August, medusae grew significantly at 0.052 d-1, thus the amount of food ingested by medusae population in situ was likely to exceed the PMFR (1.27 mg C m^?3 d^?1) during the period. In conclusion, the medusae population of higher density during June and July had limited amount of food, while those of lower in July and August ingested enough food for growth.     

上海石化总厂化工物料码头对附近水下地形变化的影响

分析了上海石化总厂化工物料码头周围水下地形工程前后的变化。指出在淤泥质岸段,由于沿岸工程的影响,造成工程附近水域动力环境的改变,水下地形随之作出相应的调整。特别在淤泥质岸段附近流急、含沙量高的水域中构筑沿岸工程,工程的水流下方一侧,水流减缓,水流挟沙能力大大减弱,出现明显的局部淤浅地形,为提高工程效益,对各工程之间的相互影响,应予以重视。     

不同营养条件下铜绿微囊藻(Microcystis aeruginosa)和小球藻(Chlorella vulgaris)的生长竞争行为

蓝藻的暴发通常是藻类之间竞争的结果,了解环境中蓝藻与其它藻类的竞争特点和生存策略对揭示藻华暴发的机制及治理具有重要意义。本文以营养竞争为例,以铜绿微囊藻(Microcystis aeruginosa)和小球藻(Chlorella vulgaris)为受试对象,通过测定细胞密度、胞内C、N、P、S四种主要元素含量以及培养基中总氮(TN)、总磷(TP)的消耗,研究不同营养等级(超富营养、富营养、中营养、贫营养)以及单独N、P限制下两种藻在单独培养和共生培养条件下的生长特征和竞争行为。结果表明:(1)在超富营养、富营养、中营养、贫营养条件时,单独培养下的两种藻生物量与营养丰富程度呈正相关;(2)共培养条件下,在高营养水平时铜绿微囊藻在竞争中占优势,低营养水平时小球藻具有竞争优势;(3)胞内C、N、P、S的测定发现,随着营养水平的下降,两种藻胞内N、P的百分含量逐渐减少,而C、S并未呈现显著变化;(4)N限制时,铜绿微囊藻的半饱和常数Ks及最大比增长率μmax均大于小球藻;P限制条件下铜绿微囊藻的半饱和常数Ks小于小球藻,而最大比增长率μmax大于小球藻。综合分析,同一营养条件下,铜绿微囊藻竞争优势的先决因子是N,小球藻是P。因此,从营养竞争与生物适应力角度考虑,降低水体中富余的N或适当提高P的浓度可让小球藻获得竞争优势,对限制单一物种的形成具有平衡作用,可作为防治藻华的潜在方法。     

胶州湾大沽河口洪水期三维水沙数值模拟研究

大沽河是胶州湾最大的入海河流,每年都会给胶州湾带来大量泥沙。本文利用三维的ECOMSED水动力-泥沙数值模型对洪水期的大沽河进行了数值模拟,得到了洪水存在期间以及洪水结束后胶州湾的余流分布、大沽河河道上中下游各层盐度、泥沙浓度随时间变化的趋势以及入海冲淡水和泥沙对胶州湾的影响。     

九龙江口鳗苗溯河生态与资源研究

九龙江口Ｌｉ苗１９９４￣１９９６年溯河期为１９９４年１１月２０至１９９５年４月底。１９９５年１２月２０日至１９９６年５月底。鳗苗溯河期水温范围１１．５￣２２．５℃,盐度１．９８￣２５．００,透明度０．２￣１．１ｍ,九龙江口打石坑－嵩屿断面溯河鳗苗资源量１９９５年１９３ｋｇ,１９９６年２０８ｋｇ;海澄断面１９９５年３５ｋｇ,１９９６年５５ｋｇ。     

基于COSMIC掩星数据分析中低纬度地区电子密度分布变化

利用COSMIC掩星2009年电子密度剖面数据,筛选数据进行网格划分,网格内数据统计平均,基于球谐函数计算模型值,分析电离层中低纬度地区最大电子密度的地磁季节变化、昼夜测分布相对变化,及地磁活动对电子密度的分布影响.结果表明,最大电子密度昼测值明显高于夜测值,在中纬度部分区域增大明显.电子密度昼测值在地磁活动期间高度150-550 km中低纬度范围为正相扰动,随纬度变化存在区域差异,随高度增加,扰动加强.     

Application of a multi‐temporal,LiDAR‐derived,digital terrain model in a landslide‐volume estimation

Sediments produced by landslides are crucial in the sediment yield of a catchment, debris flow forecasting, and related hazard assessment. On a regional scale, however, it is difficult and time consuming to measure the volumes of such sediment. This paper uses a LiDAR‐derived digital terrain model (DTM) taken in 2005 and 2010 (at 2 m resolution) to accurately obtain landslide‐induced sediment volumes that resulted from a single catastrophic typhoon event in a heavily forested mountainous area of Taiwan. The landslides induced by Typhoon Morakot are mapped by comparison of 25 cm resolution aerial photographs taken before and after the typhoon in an 83.6 km² study area. Each landslide volume is calculated by subtraction of the 2005 DTM from the 2010 DTM, and the scaling relationship between landslide area and its volume are further regressed. The relationship between volume and area are also determined for all the disturbed areas (V_L = 0.452A_L^1.242) and for the crown areas of the landslides (V_L = 2.510A_L^1.206). The uncertainty in estimated volume caused by use of the LiDAR DTMs is discussed, and the error in absolute volume estimation for landslides with an area >10⁵ m² is within 20%. The volume–area relationship obtained in this study is also validated in 11 small to medium‐sized catchments located outside the study area, and there is good agreement between the calculation from DTMs and the regression formula. By comparison of debris volumes estimated in this study with previous work, it is found that a wider volume variation exists that is directly proportional to the landslide area, especially under a higher scaling exponent. Copyright © 2013 John Wiley & Sons, Ltd.     

汶川8．0级地震与日本9．0级地震的同震响应特征——庐江地震台动水位与水温

自2000年庐江地震台数字化水位、水温观测以来,在多次大地震中水位、水温均有明显的同震效应,四川汶川8．0级地震、日本本州9．0级地震引起汤池1号井水位、水温的同震特征。动水位同震效应表现为脉冲变化,震后水位逐渐升高;水温表现为阶跃下降,震后水温缓慢恢复到正常状态。     

龙门山断裂带上“破裂空段”的发震概率研究

本文采用分层粘弹性介质模型计算了汶川地震对芦山震中产生的库仑应力加载的影响,进而结合Dieterich(1994)提出的速率状态摩擦定律给出芦山附近区域6级地震累积发震概率随时间的变化。结果显示,2013年芦山7.0级地震时其累积发震概率达18%,说明汶川地震产生的应力扰动加速了芦山地震的发生。本文还计算了汶川、芦山2次地震对其间"破裂空段"处产生的累积库仑应力扰动的影响,结合背景地震发生率,给出了"破裂空段"处6级地震累积发震概率变化。虽然计算结果可能受到大邑地震、介质模型参数的选取和背景地震发生概率等因素影响而存在一定误差,但"破裂空段"在2次强震应力加载下累积发震概率是不断增大的,因此我们认为"破裂空段"处发生中强地震的紧迫性不断增强。