SEABEAM1185多波束系统的测量精度分析及在堤防监测中的应用

通过与不同型号单波束测深仪的多种方式和角度的比测试验，验证了SEABEAM 1185多波束测深系统具有全覆盖扫测，测量范围大、速度快，测深精度和分辨率高等优点，突出其可靠性和稳定性。介绍了SEABEAM 1185系统的组成及其技术性能，并具体分析了系统在监测广东省某河道堤防险段的使用情况及应用价值。     

Study on the slope break belts in the Jurassic down-warped lacustrine basin in western-margin area, Junggar Basin, northwestern China

The Junggar Basin is one of the large-scale petroliferous basins in northwestern China. During the Jurassic Age it was a down-warped continental basin. Different types of slope break belts with different origins have been identified in the basin, including the fracture, flexure, erosional and depositional slope break belts. Fracture and flexure slope break belts were mainly developed in the western-margin area of the Junggar Basin. Slope break belts can be further divided into two types, which are basin margin and inner basin according to their geographical locations. Tectonic movements are the important origin mechanisms controlling the development of the slope break belts, such as deep-seated thrust structure, inherited paleouplift and secondary fracture movement in the basin. Obviously slope break belts are developed in episodes, developed in multi-stages and are differential in movements and can be inherited and transformed due to the changes of tectonic movements in different periods and different areas. Detailed studies indicate that slope break belts obviously control the strata onlap, the vertical lithologic succession and the vertical and lateral distribution of depositional systems. Slope break belts can control the distribution of different non-structural traps.     

The spatial and temporal distribution of grain‐size breaks in turbidites

Grain‐size breaks are surfaces where abrupt changes in grain size occur vertically within deposits. Grain‐size breaks are common features in turbidites around the world, including ancient and modern systems. Despite their widespread occurrence, grain‐size breaks have been regarded as exceptional, and not included within idealized models of turbidity current deposition. This study uses ca 100 shallow sediment cores, from the Moroccan Turbidite System, to map out five turbidite beds for distances in excess of 2000 km. The vertical and spatial distributions of grain‐size breaks within these beds are examined. Five different types of grain‐size break are found: Type I – in proximal areas between coarse sand and finer grained structureless sand; Type II – in proximal areas between inversely graded sand overlain by finer sand; Type III – in proximal areas between sand overlain by ripple cross‐laminated finer sand; Type IV – throughout the system between clean sand and mud; and Type V – in distal areas between mud‐rich (debrite) sand and mud. This article interprets Types I and V as being generated by sharp vertical concentration boundaries, controlled by sediment and clay concentrations within the flows, whilst Types II and III are interpreted as products of spatial/temporal fluctuations in flow capacity. Type IV are interpreted as the product of fluid mud layers, which hinder the settling of non‐cohesive grains and bypasses them down slope. Decelerating suspensions with sufficient clay will always form cohesive layers near to bed, promoting the generation of Type IV grain‐size breaks. This may explain why Type IV grain‐size breaks are widespread in all five turbidites examined and are commonplace within turbidite sequences studied elsewhere. Therefore, Type IV grain‐size breaks should be understood as the norm, not the exception, and regarded as a typical feature within turbidite beds.     

高红移Lyman Break星系

总结了到目前为止用所谓Lyman Break方法（亦称为UV drop方法）观测得到的高红移（z≈3）Lyman break星系的观测特征，包括光度函数、半光度半径分布、空间密度及成团性、恒星速度弥散、超星风及大尺度气体团块运动和金属丰度等。还对目前的理论工作做了综合介绍，对当前两种主要模型进行了评述并提出了作者的个人观点。     

珠江口盆地坡折带特征及其对沉积体系的控制

本文基于对覆盖全区的二维地震资料研究,在珠江口盆地识别出了大型的陆架坡折及多种小型坡折带,包括侵蚀坡折带、沉积坡折带、断裂坡折带和挠曲坡折带。不同的构造背景发育了不同的坡折带类型。自30Ma年以来,坡折带总体呈向北迁移的趋势。古近纪一早中新世中期以各种小型坡折带为主,主要控制三角洲及扇三角洲等浅水沉积的展布;早中新世中期至今,由于陆架一陆坡体系已形成,坡折带以陆架坡折为主,控制了陆架边缘三角洲及海底扇等较深水沉积的发育。     

Scale variance analysis coupled with Moran's I scalogram to identify hierarchy and characteristic scale

Scale variance is highly sensitive to multi-scale patterns of variables, which is advantageous in identifying spatial hierarchy and characteristic scale(s). However, the significance of peak(s) in scale variance cannot be statistically tested, and different spatial patterns may be obtained when different zoning systems are used to calculate scale variance. To address these two problems, this study compared the scale levels with peaks in scale variance and the scale levels at which there were breaks in the nature of spatial autocorrelation as identified by shifts in Moran's I scalogram. The estimates for three simulated landscapes showed that accordance between scale levels identified employing the two methods can be used to evaluate the significance of peaks in scale variance and choose a more reasonable zoning system. The approach of scale variance analysis coupled with Moran's I scalogram was also applied to the Xilin River Basin of Inner Mongolia, China. The most vital characteristic scale (64 × 32 km) identified for the growing-season net ecosystem productivity (NEP) of the basin was validated by other spatial pattern analysis methods such as semi-variogram, Moran's I correlogram, and wavelet variance analyses, and the directionality of the chosen zoning systems was found to be similar to the orientation of actual dominant vegetation type patches. The results demonstrate that Moran's I scalogram can be used to improve the interpretation of the results of scale variance analysis and increase the reliability of scale variance analysis for landscapes having a repetitive patch pattern or gradient variation and that the proposed approach is suitable for identifying the hierarchy and the characteristic scales of patterns or processes. In summary, this study used a simple approach to solve two problems in scale variance analysis, thereby improving the methodology and enhancing the theoretical basis of multi-scale analysis.     

Spatiotemporal simulation and risk analysis of dam-break flooding based on cellular automata

Chapinghe Barrier Lake was the largest among the barrier lakes formed in the aftermath of the magnitude 5.12 Wenchuan Earthquake. A rapid quantitative method for the evaluation of potential risk to lives and properties downstream was of the utmost importance for disaster management. The proposed method is based on spatiotemporal simulation using different dam-break scenarios and downstream hazard distribution analyses. This article adopts a cellular automata (CA) model to synthetically integrate multiple sets of geographic layers, including those containing the models needed for routine computation of flood hazards and those needed for vulnerability analysis of the people living downstream. A CA-based simulation and analysis method integrating hydrologic/hydraulic mechanisms is herein introduced, and relevant techniques are investigated. Our prototype experiment demonstrates that the proposed CA-based flood-hazard model can be conveniently integrated into a digital earth system and can further provide real-time simulation analyses of dam-break flood risks.     

基于围岩片帮形迹的宏观地应力估计方法探讨

基于深部地下勘探隧洞围岩应力型片帮破坏是岩体初始地应力作用的最直观结果的认识,建立借助围岩片帮形迹分析工程区岩体宏观地应力的估计方法。该方法通过对比分析地应力作用下多个交叉隧洞围岩的片帮空间分布特征和烈度强弱关系,建立岩体3个初始主应力的空间大小和方向关系;采用片帮劈裂纹方位角统计获得岩体最大主应力方向;依据片帮的应力门槛值和起裂应力门槛值估算出3个主应力量值。现场实测地应力数据和多工况数值计算分析都有力地表明,借助该分析方法获得的白鹤滩右岸厂址区域三维地应力是科学、合理的,这也为深入认识工程区地应力特征提供了一条新思路     

Dam-break flood simulation under various likely scenarios and mapping using GIS: Case of a proposed dam on River Yamuna, India

The precision modeling of dam break floods can lead to formulation of proper emergency action plan to minimize flood impacts within the economic lifetime of the assets.Application of GIS techniques in integration with hydrological modeling for mapping of the flood inundated areas can play a momentous role in further minimizing the risk and likely damages.In the present study,dam break analysis using DAMBRK model was performed under various likely scenarios.Probable Maximum Flood (PMF)calculated for a return period of 1000 years using deterministic approach was adopted for dam break analysis of the proposed dam under various combinations of breach dimensions.The available downstream river cross-sections data sets were used as input in the model to generate the downstream flood profile.Dam break flow depths generated by the DAMBRK model under various combinations of structural failure are subsequently plotted on Digital Elevation Model(DEM)of the downstream of dam site to map the likely affected area.The simulation results reveals that in one particular case the flood without dam may be more intense if a rainfall of significant intensity takes place.     

Highly restricted gene flow between disjunct populations of the skunk clownfish (Amphiprion akallopisos) in the Indian Ocean

The skunk clownfish (Amphiprion akallopisos) has a disjunct distribution, occurring in the Eastern Indian Ocean (EIO) and the Western Indian Ocean (WIO), separated by several thousands of kilometres. Information on connectivity of marine species is very important for the correct spacing of marine protected areas, a powerful instrument for the protection of coral reefs. The population genetic structure of A. akallopisos was analysed in order to investigate connectivity amongst populations and to explain the disjunct distribution of the species. A fragment of the mitochondrial control region was used to investigate the genetic population structure. Fin clips were collected from 263 individuals at 14 sites in the WIO and three sites in the EIO. The obtained DNA sequences were used to calculate genetic diversity, evaluate demographic history and to construct a haplotype network. An analysis of molecular variance (AMOVA) was conducted to evaluate the significance of the observed genetic population structure. None of the identified 69 haplotypes was shared between the WIO and EIO. Haplotype as well as nucleotide diversity was considerably higher in the EIO than in the WIO. Significant genetic population structure was revealed by an AMOVA with an overall φ_st‐value of 0.28 (P < 0.001) in the Indian Ocean. The overall AMOVA (φ_st = ?0.00652) was not significant in the EIO, but was significant in the WIO (φ_st = 0.016; P < 0.01). Demographic analysis indicated population expansion in the EIO and WIO. Population genetic analysis revealed highly restricted gene flow between the EIO and WIO. Genetic diversity was much higher in the EIO than in the WIO, suggesting that the EIO is the geographical origin of the species. Given the large distance between the disjunct populations and the short pelagic larval duration, long‐distance dispersal is rather unlikely. A stepping stone model involving islands in the Central Indian Ocean is a more likely scenario for colonization of the WIO.