A note on the seafloor coupling characteristics of the new ONR ocean-bottom seismometer

A series of transient tests were conducted to determine the seafloor coupling characteristics of a new ocean-bottom seismometer (OBS) developed for the United States Office of Naval Research (ONR). The OBS comprises a large recording package and a separate sensor package that is deployed from the recording package. In addition to the coupling characteristics of both the sensor and the recording packages, the seismic energy radiated from the main recording package as a result of motion of the recording package was measured. The observed vertical coupling resonances of both the recording package and the sensor package are in good agreement with those predicted by a simple model of soil-structure interaction. The most important result of this study is that significant energy is radiated from the recording package in response to horizontal motions of the recording package. When the sensor package is 1 m from the recording package, the amplitude of the recorded signal is similar to that recorded in the recording package. In the field, this effect will result in distortion of seismic signals and increased background noise recorded by the sensor package if the recording package is disturbed by seafloor currents or biological activity. The amplitude of this signal attenuates by approximately a factor of two as sensor/recorder separation is increased from 1 to 6 m, suggesting that an improved response can be achieved by increasing the separation between the recording package and the sensors. This effect is much less severe for vertical disturbances of the recording package.     

Bowen数和东中国海Bowen数分布

本文讨论Bowen数的意义、功能和计算法。同时,依据多年水文气象实测资料作统计,计算出东中国海的Bo值。其结果绘制成1月至12月的月平均分布图,从而对本海域的Bo分布特点作详细分析介绍。     

Distribution of soft-bottom polychaetes in two coastal areas of the Tyrrhenian Sea (Italy): Structural analysis

Multidimensional statistical analysis was used to study the polychaete distribution in soft-bottoms of two coastal areas of the Tyrrhenian Sea (Italy), which are influenced by the discharges of the rivers Tiber and Ombrone. In both areas the distributional patterns of these organisms are determined mainly by sediment types and related factors such as hydrodynamics, river input, and sedimentation. The grain-size gradient from the coast to the open sea affects not only species composition, but also species richness, diversity and abundance.In both areas three main communities have been identified: a sandy biocoenosis, a mixed-sediment biocoenosis and a muddy biocoenosis. The sandy coastal community is characterized by only a few species, while the intermediate zone of sandy-mud sediments presents the highest species richness and diversity. At the mouth of the River Tiber the influence of the river is more evident than at the mouth of the River Ombrone. This is due to the Tiber's greater river flow, which determines an environmental uniformity and a ‘cenotic continuum’ from sandy to muddy communities. This does not occur at the mouth of the Ombrone, where the river flow is less important and the polychaete communities are better defined.     

海冰业务化预报基础研究进展

本文概述了我国近年来在海冰预报基础研究方面的工作进展情况,着重介绍了在我国海冰的气候成因、海冰分布特征和变化规律等方面的研究成果.     

A technique for conducting seismic refraction experiments on the ocean bed using bottom shots

A technique has been devised for firing arrays of bottom shots on the ocean bed in depths upto 4000 m or more. Ten kilogram explosive charges are dropped from the surface while the shooting ship is navigated acoustically. They are detonated at preset times by an electronic timer which initiates an electrical detonator, detonating cord and cast PETN/TNT explosive. Ranges to ocean bottom seismographs, and the shot instants, can be calculated from the arrival-time differences of the direct and surface-reflected water waves. The accuracy, which is dependent on water-depth and range, was better than 22 m in range and 14 msec in shot instant for our experiments.     

台湾海峡中、北部上升流区浮游有孔虫的生态研究

分析１９８７—１９８８年在台湾海峡中、北部用浮游生物网采集的水层中的浮游有孔虫标本，研究调查海区浮游有孔虫的生态分布特征及其与海水温度和盐度的关系。结果表明：该海区浮游有孔虫计有１６种，以泡抱球虫Ｇｌｏｂｉｇｅｒｉｎａｂｕｌｌｏｉｄｅｓ为主要优势种类，其次是袋拟抱球虫Ｇｌｏｂｉｇｅｒｉｎｏｉｄｅｓｓａｃｃｕｌｉｆｅｒ和红拟抱球虫Ｇ．ｒｕｂｅｒ。在夏季的７月和８月（特别是７月），浮游有孔虫密集在福建中部沿岸的南日岛至闽江口外海海域一带沿岸水域，其中９０％以上的个体由泡抱球虫组成。此现象推测与夏季出现在福建沿岸的上升流活动有关。     

Study on Key Technology of Using Shell Sand as Backfill for Sea Reclamation

1 .IntroductionEpicontinental sea or land could formfromcontinental shelf because of the decreasing sea levelduring Quaternary.There is a large-area shell sand deposit more than ten meters thick in the neriticzone of China .To use the abundant marine shell sandresource as engineering material for ocean engi-neering and port engineeringis veryimportant .Sand (Gred and Bjorn,1999) ,fine sand (Zhangetal .,2002) , mediumand coarse sand (Qiuet al .,1995) ,highly weathered stone ballast (Zhanetal…     

东海沿岸海区垂直环流及其温盐结构动力过程研究Ⅱ．温盐结构

对于本研究采用的动力学模型及其垂直环流的模拟结果已在第Ⅰ部分论述。作者将对与垂直环流对应的温、盐结构进行分析。温度和盐度模拟结果表明：冬季东海沿岸海区的温、盐分布均为近岸低、外海高;近岸温、盐呈垂直均匀分布,在外海出现分层,其温度为表层高、底层低,而盐度却为表层和底层高,中层偏低,长江口以南的近表层以下形成自近岸伸向外海的弱低盐水舌;长江冲淡水区及长江口以北和其以南外海的近表层有温、盐跃层生成,深底层温、盐呈均匀分布,且保持低温高盐特征;随着海区自北往南纬度的降低,岸坡和水深的增大及沿岸下降流的增强,温度和盐度自近岸至外海的垂直均匀分布跨度逐渐变窄;外海近表层的温、盐跃层强度自北至长江口逐渐增强,而自长江口至南逐渐减弱,其位置自北往南逐渐上移;冬季沿岸下降流使长江冲淡水区的盐跃层变厚。夏季海区的温度分布为近岸和外海高,近岸稍远出现冷水涌升,垂向上呈现显著分层,盐度分布为近岸低、外海高;长江冲淡水区及杭州湾以南外海的次表层存在温、盐跃层,其跃层以上出现混合层,且保持高温低盐特征,跃层以下温、盐大致呈均匀分布,并保持低温高盐特征;随着海区自南往北纬度的增高、岸坡和水深的减小及沿岸上升流自南至长江口和自长江口至北的增强和继而减弱,长江冲淡水区的温、盐跃层强度自南至长江口逐渐增强,而自长江口至北逐渐减弱,外海次表层的温、盐跃层强度却自南至长江口逐渐减弱,自长江口至北又逐渐增强,其温、盐跃层的位置自南往北逐渐上移;夏季沿岸上升流使长江冲淡水区的盐跃层变薄。