Projective ordination by SIMCA: A dynamic strategy for cost-efficient environmental monitoring around offshore installations

A method for environmental monitoring using benthic species profiles as input is developed in this work. The method, referred to as projective ordination, utilises local principal component modelling (SIMCA) to obtain a cross-validated model which spans the natural variation in a region around offshore oil-producing installations. The borderline between regions with disturbed and non-disturbed species communities is subsequently decided from the residual distribution. This distribution is used to design an approximate F-test for assessing whether a community at a particular sampling location is disturbed or not. If so, the nature of the disturbance is determined by projecting the data on the PC model.Projective ordination utilises information from previous surveys to define the permissible variation in species communities, i.e. the limit of the natural variation. In addition, the method is dynamic, in a sense that the sampling locations may vary from survey to survey.Furthermore, our analysis shows that the customary number of replicate samples per station can be reduced. Modelling with only four randomly chosen replicates out of the complete set of five for each sampling location, does not affect the model significantly. On the other hand, taking only 3 replicates into account leads to significant divergences.A model based on the 1990 and 1993 surveys at the Statfjord field is presented as an example of the technique.     

Dynamic interaction of twin vertically overlapping lined tunnels in an elastic half space subjected to incident plane waves

The scattering of plane harmonic P and SV waves by a pair of vertically overlapping lined tunnels buried in an elastic half space is solved using a semi-analytic indirect boundary integration equation method. Then the effect of the distance between the two tunnels, the stiffness and density of the lining material, and the incident frequency on the seismic response of the tunnels is investigated. Numerical results demonstrate that the dynamic interaction between the twin tunnels cannot be ignored and the lower tunnel has a significant shielding effect on the upper tunnel for high-frequency incident waves, resulting in great decrease of the dynamic hoop stress in the upper tunnel; for the low-frequency incident waves, in contrast, the lower tunnel can lead to amplification effect on the upper tunnel. It also reveals that the frequency-spectrum characteristics of dynamic stress of the lower tunnel are significantly different from those of the upper tunnel. In addition, for incident P waves in low-frequency region, the soft lining tunnels have significant amplification effect on the surface displacement amplitude, which is slightly larger than that of the corresponding single tunnel.     

Can unbiased source be retrieved from anisotropic waveforms by using an isotropic model of the medium?

Anisotropy is frequently present in geological structures, but usually neglected when source parameters are determined through waveform inversion. Due to the coupling of propagation and source effects in the seismic waveforms, such neglect of anisotropy will lead to an error in the retrieved source. The distortion of the mechanism of a double-couple point source located in an anisotropic medium is investigated when inverting waveforms using isotropic Green's functions. The anisotropic medium is considered to be transversely isotropic with six levels of anisotropy ranging from a fairly weak to rather strong anisotropy, up to about 24% in P waves and 11% in S waves. Inversions are based on either only direct P waves or both direct P and S waves. Two different algorithms are employed: the direct parametrization (DIRPAR, a nonlinear algorithm) and the indirect parametrization (INPAR, a hybrid scheme including linear and nonlinear steps) of the source. The orientation of the double-couple mechanism appears to be robustly retrieved. The inclination of the resulting nodal planes is very small, within 10° and 20° from the original solution, even for the highest degree of anisotropy. However, the neglect of anisotropy results in the presence of spurious isotropic and compensated linear-vector dipole (CLVD) components in the moment tensor (MT). This questions the reliability of non-double-couple components reported for numerous earthquakes.     

不同云滴数浓度参数化方案对硝酸盐气溶胶 第一间接效应影响的比较研究

在区域气候化学模式系统（RegCCMS）中,分别采用Hegg、Hansen、Ghan、Jones等4种云滴数浓度参数化方案,模拟研究了2003年10月硝酸盐气溶胶的浓度分布和第一间接气候效应,并对不同方案进行比较。结果表明,不同方案模拟的硝酸盐气溶胶分布大体上一致,主要集中在河南、山东、河北、四川等地,地面浓度最大值达18 μg/m3。Hegg、Hansen、Ghan、Jones等 4种云滴数浓度参数化方案计算得到的由硝酸盐气溶胶所造成的第一间接辐射强迫全国平均值分别为-148、-205、-161和-140 W/m2。4种方案模拟的硝酸盐气溶胶间接效应都表现为近地面气温下降,降水减少,其中Hansen方案的间接效应最强,Ghan、Hegg方案次之,Jones方案最弱。     

Functional diversity of fish and invertebrates in coral and rocky reefs of the Eastern Tropical Pacific

To define the functional groups of fish and macroinvertebrates in the Eastern Tropical Pacific (ETP), visual censuses were performed in 18 areas of four biogeographic provinces: Cortés, Mexican, Panamic and Oceanic Islands. A total of 257 fish and macroinvertebrate species were recorded, and from them, 27 morpho‐functional groups (MFGs) were constructed on the basis of trophic level, maximum size, taxonomy and morphology. Biomass, richness, diversity and evenness of MFGs were calculated for each province and compared statistically; a regression analysis between taxonomic and functional diversity was conducted to observe the relationship between these two indicators. There were significant differences in all ecological indices (p < .002), highlighting the high biomass and richness of MFGs in the Cortés and Oceanic Islands provinces (>400 g/m²), associated with the influence of cold currents in the northernmost region and less fishing pressure in protected areas. A decreasing pattern of MFG richness towards the tropics was observed, which demonstrates that in the ETP, the relationship between habitat heterogeneity and species diversity has been translated into functional complexity. The Mexican province was the most functionally diverse (biomass well distributed in the MFG; H′ = 0.46 ± 0.009). Related to this, it is predicted that biomass is biased towards certain functional groups (i.e., large carnivores), which shows that the H′ index of the MFG is not a good indicator of the conservation status of ETP reefs. Finally, regression analysis suggests that functional diversity increases at low species diversity but eventually reaches an asymptote (almost all possible functions are represented).     

跨河水准测量的一种新方法

提出了GPS RTK技术在跨河水准测量中的新应用，分析了影响RTK高程实时解算精度的主要因素，RTK技术应用于跨河水准测量的实施原则、成果比较及精度分析，并提出了一些有益的建议。     

WA-PLS diatom-based pH, TP and DOC inference models from 42 lakes in the Abitibi clay belt area (Québec, Canada)

The relationship between surficial sediment diatom species and measured environmental variables was explored in lakes from the Abitibi region of western Quebec. Diatom assemblages in 42 lakes were identified and their relationship with measured environmental variables was examined using multivariate statistical methods. Canonical correspondence analysis with forward selection and Monte Carlo permutation tests revealed that the three environmental variables pH, TP and DOC each accounted for statistically significant fractions of the variation in diatom taxa. A training set with 164 modern diatom taxa was used to derive transfer functions for lake-water pH, TP and DOC using weighted-averaging-partial-least-squares (WA-PLS) techniques. The models were developed to infer lake water pH, TP and DOC within the ranges 4–8 for pH, 2.75–30.0 g l^–1 for TP, and 2.9–18.5 mg l^–1 for DOC. These quantitative inference models may now be used to help identify and estimate the effects of natural disturbances on the biogeochemistry of Abitibi lakes during their historical development.     

A framework for economic loss estimation due to seismic transportation network disruption: a spatial computable general equilibrium approach

This paper presents a framework for assessing the economic impact of disruption in transportation that can relate the physical damage to transportation networks to economic losses. A spatial computable general equilibrium (SCGE) model is formulated and then integrated with a transportation model that can estimate the traffic volumes of freight and passengers. Economic equilibrium under a disruption in the transportation network is computed subject to the condition that the adjustment of labor and capital inputs is restricted; the model reflects slow adjustment of these linked to the state of recovery. As a case study, the model reviews the large Niigata-Chuetsu earthquake of 2004. Considering the damage to the transportation infrastructure, the model indicates the extent of the economic losses arising from the earthquake distributed over regions as a consequence of the intra- and interregional trade in a regional economy. The results show that 20% of the indirect losses occur in the Niigata region directly affected by the earthquake, whereas 40% of the total losses are experienced in the Kanto region and non-negligible losses reach rather remote zones of the country such as Okinawa.     

珠江口及邻近水域鱼类群落结构研究

根据1986～1987年珠江口及邻近水域底拖网鱼类采样资料,运用系统聚类与排序等多元分析方法和群落多样性指数,研究该水域鱼类群落结构及其与环境因素的关系,分析结果把该水域鱼类划分为淡水、河口和沿岸3个群落,分别位于莲花山,虎门河道、珠江河口伶仃洋和珠江口浅海水域,各群落结构组成呈沿盐度梯度而成带分布的格局.淡水群落结构简单稳定,沿岸群落结构比较复杂,河口群落受水动力过程和生物活动影响最大,群落结构的季节变化较为显着.