广东省东部地区背景噪声面波群速度层析成像

We perform Rayleigh wave tomography in east Guangdong and its surrounding regions by applying the ambient noise method to broadband data recorded at 26 stations from Guangdong, Fujian and Jiangxi Digital Seismic Networks. Cross-correlations of vertical- component ambient noise data are computed in one-day segments and stacked over seven months from March to September, 2011. Then Rayleigh wave group dispersion curves are measured using the frequency-time analysis method. Group velocity maps at periods from 5s to 15s are inverted. The resulting group velocity maps generally show good correlation with tectonic features, reflecting the velocity variations in the shallow crust. The basin areas are clearly resolved with lower group velocities at the short periods due to thick sedimentary layers, and the mountain areas with higher group velocities due to thin sedimentary layers. The variations of group velocity on the map can draw out the distribution of basins and mountains in study areas. The geothermal field can change the group velocity obviously, and lower group velocities are always found in high geothermal areas. The velocity maps indicate that a low-velocity layer may be found in the study areas.     

A preliminary study on mean-field decomposition

Two kinds of the empirical orthogonal function analysis method for decomposing the mean-field are developed and a comparison is made between them. It is proved that the mean-field can be decomposed using eigenvectors obtained from anomaly-field decomposition, and that more information can be obtained. An example of sea bottom mean temperature analysis shows its remarkable effect in depicting the distribution features of various factors, such as cold water mass, currents and radiation.A few problems concerning the efficiency of the method are discussed and two matrices of relationship which represent the space-time characteristics of the field are derived. The formulae of space-time transformation are obtained conveniently.     

AN ANALYSIS OF MODIFIED WATER MASSES IN THE YELLOW SEA AND EAST CHINA SEA

The waters in the shallow part of the Yellow Sea and East China Sea are affected greatly by climatic and geographical conditions and fail to possess homogeneity and conservativeness like oceanic waters. They have apparent difference in modified degrees, so we may regard a certain range of mixed water as a relatively independent one. In fact, the study of water masses in the shallow sea means a modified analysis of waters. The idea of modified water masses is introduced, i. e., a water body which holds the similar physical and chemical characters, occupies a certain space, and varies seasonally and regularly. On the T-S diagram, it displays as a certain amount of points aggregated together, the centre of which changes regularly and may have a process of combination and separation.According to the clustering method, there are eight modified water masses in this area. They may also be divided into three salinity types. On the T-S diagram, the points concerning temperature and salinity of different modified     

划分变性水团边界的温盐点聚对照法与东海西部海区变性水团的分析

分析水团已有许多方法,其中多数是分析大洋水团问题的[3][4][5][6][7][8],用于浅海有一定困难;关于分析浅海水团问题、我国进行了一些研究[1][2],主要解决确定水团边界问题.其中“组成比例法”能比较定量地确定出水团边界的位量,但这个方法要求参加混合的水团要有明确的核心值.由于水团的核心值难于确定,特别是在不同季节调查海区范围经常变动的情况下,若把被调查海区内温盐的极值当作核心值来处理.必然影响到比例中点的相应变动,所确定的水团边界也就不准确了.     

东海北部区域底层冷水团的形成及其季节变化

本文着重探讨东海北部底层冷水(北部冷水)的形成原因、基本特征和季节变化过程。指出北部冷水系冬季黄海沿岸水南下向东海输送低温水并与外海高盐水混合变性形成的。其位置随季节变化而有明显的移动规律,即先由西向东移,而后向北收缩。大体上可分为四个阶段:冷水舌离岸期,北部冷水半封闭期,北缩消亡期和更新期。文中分析了上述变化的原因,较详细地阐述了黄海沿岸水沿陆架下沉与黑潮次—中层混合水爬升的关系及其对北部冷水的影响。分析了北部冷水与黄海冷水团的关系。     

浅海变性水团的软划分

In this paper, the principle and steps for differentiating water masses by fuzzy cluster method are introduced, and a scalar formula bsed on Euclidean distance and a method for determining objectively the number of water masses by F-test are proposed. Consequently, a method and specific steps for differentiating modified water masses in shallow sea according to fuzzy elastic classification are given. Computation of the membership degree in which each sample belongs to every water mass determines conveniently and quantitatively the cores, boundaries of water masses and mixed zones. An example for the Huanghai Sea and East China Sea is shown and compared with previous results.     

变性水团隶属函数的椭圆拟合法

应用模糊子集的概念描述浅海区变性水团。讨论了变性水团隶属函数在θ—S图解上“落影”的形式。文中给出用椭圆拟合法建立隶属函数的实例。     

从混合变性过程看水团隶属函数的建立

将研究海区中的水团,视为论域中的模糊子集。用关于海水中保守浓度的混合理论,来讨论水团在混合变性过程中隶属函数的可能形式,可为变性水团隶属函数建立提供依据。本文的结果可推广应用于浅海,文中给出了实例和讨论。     

海洋水团的Fisher型逐步判别预报

判别分析是多元分析方法之一,我们将其应用于海洋水团的判别预报。用逐步判别的方法挑选因子,依每个因子的Wilks量进行F—检验,逐步地将判别“能力”强的因子选入。同时将由于其他因子组合而相形见绌者及时剔除。根据矩阵变换的信息,给出了Fisher型逐步判别预报式。将北黄海冷水团强度预报作为示例,给出了筛选因子及建立判别式的全过程。用历史资料检验了预报效果。与习用的Bayes型逐步判别预报进行了对比。