根据特定场地的设计地震对设计地震动的一种评估方法

引言地震地面运动的特征取决于震源、地震波的传播路径和局部场地条件。近来,地震学、地震工程学和地质学等领域积累了大量有价值的知识,为评估地震动提供了可利用的资料。实际上,为了设计实用的建筑物,首     

利用超导重力仪数据对2004年Mw=9级苏门答腊地震后极低简正模式的高分辨率分析

2004年12月26日苏门答腊一安达曼地震（Mw=9）强烈地激发了低频地震简正模式，为改善极低地震简正模式频率及阻尼测量提供了难得的机会。为改进地球一维密度模型，需对低于1mHz的地震简正模式的频率分裂进行精确估算。本次地震中，首次在超导重力仪和地震波记录无叠加的情况下观测到2S1。本文报告来自11个观测台测得的超导重力仪数据的分析。单个观测台的超导重力仪记录频谱清晰地显示了0S2分裂成5个完全可分辨的单线，0S3分裂成7个单线。给出的结果表明超导重力仪可为低频地震模式的精确分析提供高质量数据。     

慢地震的定标律

最近,发现了一系列异乎寻常的地震现象,包括间歇性深部颤动(Obara,2002)、低频地震(Katsumata and Kamaya,2003)、甚低频地震(Itoet al,2006)、慢滑动事件(Hirose and Obara,2005)及寂静地震(Hi-roseet al,1999;Kawasakiet al,1995,2001;Ozawaet al,2002;Kostaglodovetal,2003)。已经表明,就像常规地震一样,产生这些地震的原因都是剪切滑动,只是特征持续时间长些,而且辐射出的地震能量要少许多。在此我们证明,这些慢事件遵循着一种简单的、统一的定标关系,这种关系使其特性与通常地震间具有明显差别。我们发现,它们的地震矩与特征持续…     

Changes in zooplankton abundance and diversity after ballast water exchange in regional seas

A study of the efficiency of ballast water exchange (BWE) in regional seas was carried out to assess this management method in reducing the risk of introducing non-native species. Zooplankton samples were taken before and after exchange on ten voyages where BWE took place (North Sea, English Channel, Irish Sea and Bay of Biscay). Zooplankton abundance was always reduced after exchange, but diversity increased on eight occasions. The greatest changes occurred when the source port water was of low salinity and when exchange took place in deeper waters further from land. However, it was clear that BWE did not remove all the source port taxa and this method is unlikely to provide a consistent and effective method of managing ballast water in regional seas.     

Extended probit mortality model for zooplankton against transient change of PCO(2)

The direct injection of CO(2) in the deep ocean is a promising way to mitigate global warming. One of the uncertainties in this method, however, is its impact on marine organisms in the near field. Since the concentration of CO(2), which organisms experience in the ocean, changes with time, it is required to develop a biological impact model for the organisms against the unsteady change of CO(2) concentration. In general, the LC(50) concept is widely applied for testing a toxic agent for the acute mortality. Here, we regard the probit-transformed mortality as a linear function not only of the concentration of CO(2) but also of exposure time. A simple mathematical transform of the function gives a damage-accumulation mortality model for zooplankton. In this article, this model was validated by the mortality test of Metamphiascopsis hirsutus against the transient change of CO(2) concentration.     

The role of organochlorines in cancer-associated mortality in California sea lions (Zalophus californianus)

Wild California sea lions (Zalophus californianus) have an unusually high prevalence of neoplasms (18% of stranded dead adults) and high levels of contaminants. The contribution of organochlorine (OC) tissue burdens to the probability of sea lions dying from carcinoma was explored using a logistic regression model. Levels of PCBs and DDTs were determined in blubber of sea lions diagnosed with metastatic carcinoma and animals that had died from non-carcinoma-related incidents (e.g., gunshot, domoic acid poisoning). Animals with carcinoma had higher mean concentrations (based on wet weight) of PCBs and DDTs (more than 85% and 30% higher, respectively) in blubber than did sea lions without carcinoma; the highest concentrations of OCs in the sea lions affected with carcinoma were measured in the males. Blubber thickness was significantly different between the two groups of sea lions, but after controlling for this difference, there was still a significant effect of PCBs, but not DDTs, on the probability of sea lions dying with carcinoma. Age, sex, mass and length did not affect the probability of dying from carcinoma.     

Ecotoxicity assessment of natural attenuation effects at a historical dumping site in the western Baltic Sea

During the late 1950s and early 1960s of the past century, industrial waste material highly enriched in various contaminants (heavy metals, PAHs) was dumped in the inner Mecklenburg Bay, western Baltic Sea. Large-scale shifts in the spatial distribution of heavy metals in surface sediments were mapped by geochemical monitoring in the mid-1980s and 12 years later in 1997. A further study in 2001 was designed to investigate the small-scale spatial distribution of contaminants inside, on top of, and around the historical dumping ground and to examine possible effects to benthic organisms (Arctica islandica, microbiological toxicity tests). The site is located within an area characterized by a discontinuous deposition of fine sediments, but net sedimentation rate of about 3mm/y led ultimately to a gradual coverage of the dumped material. During the first decades after the dumping, about half of the originally dumped material was already spread over the surrounding area as a result of sediment dynamics and re-suspension processes. Recent sediments of the historical dump site are still significantly enriched in heavy metals and PAHs. Microbiological toxicity test results were positive, though uptake of contaminants in mussels was found to deviate only slightly from that of a non-contaminated reference station due to a gradual dilution and decrease in bioavailability of the contaminants.     

Support vector machines (SVMs) for monitoring network design

In this paper we present a hydrologic application of a new statistical learning methodology called support vector machines (SVMs). SVMs are based on minimization of a bound on the generalized error (risk) model, rather than just the mean square error over a training set. Due to Mercer's conditions on the kernels, the corresponding optimization problems are convex and hence have no local minima. In this paper, SVMs are illustratively used to reproduce the behavior of Monte Carlo-based flow and transport models that are in turn used in the design of a ground water contamination detection monitoring system. The traditional approach, which is based on solving transient transport equations for each new configuration of a conductivity field, is too time consuming in practical applications. Thus, there is a need to capture the behavior of the transport phenomenon in random media in a relatively simple manner. The objective of the exercise is to maximize the probability of detecting contaminants that exceed some regulatory standard before they reach a compliance boundary, while minimizing cost (i.e., number of monitoring wells). Application of the method at a generic site showed a rather promising performance, which leads us to believe that SVMs could be successfully employed in other areas of hydrology. The SVM was trained using 510 monitoring configuration samples generated from 200 Monte Carlo flow and transport realizations. The best configurations of well networks selected by the SVM were identical with the ones obtained from the physical model, but the reliabilities provided by the respective networks differ slightly.     

Concentration of polychlorinated biphenyls (PCBs) in beached resin pellets: variability among individual particles and regional differences

Concentrations of polychlorinated biphenyls (PCBs) in beached resin pellets were examined to reveal variability between individual particles and differences among beaches. Fifty-five resin pellets from a beach in Tokyo were individually analyzed for PCBs, and showed concentrations ranging from <28 to 2,300 ng/g. This indicates that concentrations are highly variable between particles. Among several characters, discoloration (e.g., yellowing) had a positive relationship with PCB concentration: discolored pellets contained more PCBs than others on most of the beaches sampled. Given the color-selective ingestion of food by some organisms, this may be ecotoxicologically important. Measurements of samples from 47 beaches in Japan showed regional differences in PCB concentrations in resin pellets consistent with those in mussels. Sporadic high concentrations of PCBs were also found in pellets from remote islands, suggesting that resin pellets could be the dominant route of exposure to the contaminants at remote sites. The similarity of PCB concentrations between resin pellets and mussels suggests a potential use of resin pellets to monitor pollution in seawater.