存在低刚性不均匀体情况下的走滑断裂

在含有椭圆包体的介质中，利用由３型裂纹组成的二维模型分析了不均匀介质中的走滑断裂，以例评估局部或层状不均匀体对断裂发展的影响，表征和控制不均匀介质中断层的主要特征是有效剪切应力的空间变化，有效剪切应力变化范围可解释同一地区的地震事件的各种不同应力降值，在含有低刚性不均匀体的介质中的应力场最明显特征是在不均匀体内有效剪切应力大幅度减少，这个结果可以用来解释沉积层中动态扩展的破裂受到抑制作用，同时它也     

海洋半球台网计划(OHP)与海底地震观测系统的发展

简述了基于海洋半球台网计划(OHP),由日本建立的OHP地震台网、OHP数据中心,日本研制的海底地震观测系统,由ODP(大洋深钻计划)Leg191布设的海底钻孔宽频带地震观测站的总体进展.也阐述了近年来我国自行研发的海底地震观测系统的现状,并提出在我国沿海大陆架海域筹建海底钻孔式长期地震观测站的建议与设想.     

Sensitivity and cost considerations for the detection and eradication of marine pests in ports

Port surveys are being conducted in Australia, New Zealand and around the world to confirm the presence or absence of particular marine pests. The most critical aspect of these surveys is their sensitivity-the probability that they will correctly identify a species as present if indeed it is present. This is not, however, adequately addressed in the relevant national and international standards. Simple calculations show that the sensitivity of port survey methods is closely related to their encounter rate-the average number of target individuals expected to be detected by the method. The encounter rate (which reflects any difference in relative pest density), divided by the cost of the method, provides one way to compare the cost-effectiveness of different survey methods. The most cost-effective survey method is site- and species-specific but, in general, will involve sampling from the habitat with the highest expected population of target individuals. A case study of Perna viridis in Trinity Inlet, Cairns, demonstrates that plankton trawls processed with gene probes provide the same level of sensitivity for a fraction of the cost associated with the next best available method-snorkel transects in bad visibility (secchi depth=0.72 m). Visibility and the adult/larvae ratio, however, are critical to these arguments. If visibility were good (secchi depth=10 m), the two approaches would be comparable. Diver deployed quadrats were at least three orders of magnitude less cost-effective in this case study. It is very important that environmental managers and scientists perform sensitivity calculations before embarking on port surveys to ensure the highest level of sensitivity is achieved for any given budget.     

Monitoring persistent organic pollutants in leatherback turtles (Dermochelys coriacea) confirms maternal transfer

To assess threats to endangered species, it is critical to establish baselines for contaminant concentrations that may have detrimental consequences to individuals or populations. We measured contaminants in blubber and fat from dead leatherback turtles and established baselines in blood and eggs in nesting turtles. In fat, blubber, blood and eggs, the predominant PCBs were 153 + 132, 187 + 182, 138 + 163, 118, and 180 + 193. Total PCBs, 4,4′-DDE, total PBDEs and total chlordanes were significantly and positively correlated between blood and eggs, suggesting maternal transfer. Significant positive relationships also existed between fat and blubber in stranded leatherbacks. Less lipophilic PCBs appeared to more readily transfer from females to their eggs. PBDE profiles in the four tissues were similar to other wildlife populations but different from some turtle studies. Concentrations were lower than those shown to have acute toxic effects in other aquatic reptiles, but may have sub-lethal effects on hatchling body condition and health.     

Benthic macroinvertebrates as indicators of environmental deterioration in a large microtidal estuary

This study tested the hypothesis that, during recent years, the benthic macroinvertebrate fauna of the large basin of the Swan-Canning Estuary has changed in ways consistent with deteriorating environmental conditions in that estuary. Between 1986/7 and 2003/4, the compositions of that fauna altered markedly at the species and even family levels. Thus, the densities and number of species of molluscs, and especially of crustaceans, which are particularly susceptible to environmental stress, declined, while those of the more tolerant polychaetes increased. However, taxonomic distinctness declined consistently only at one of the four widely-spaced sampling sites and the dispersion of samples did not differ markedly between periods, indicating that the benthic fauna has not undergone such extreme changes as in the nearby Peel-Harvey Estuary. It is thus proposed that benthic macroinvertebrates can act as important indicators of the severity of environmental degradation in microtidal estuaries in regions where such perturbations are increasing.