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691.
994年9月采集了珠江口表层海水水样,并对其溶解态的K+、Na+、Ca2+、Mg2+、SO2-4、Cl等化学要素进行了测定。结果表明,珠江口调查海域表层水中溶解态的K+、Na+、Ca2+、Mg2+、SO2-4主要受陆源淡水与外海水物理混合稀释的影响,与Cl具有良好的直线正相关;Ca2+/Cl、SO2-4/Cl明显高于大洋水相应比值,Na+/Cl、Mg2+/Cl略高,而K+/Cl比大洋比值低;在与中国其它各主要河口表层水对应Cl比较中,珠江口的SO2-4/Cl较高,而Ca2+/Cl,Mg2+/Cl比值居低;上述各主要常量离子和Cl的等值线均沿自北向南走向递增。 相似文献
692.
对地震前兆异常的一些再思考 总被引:11,自引:4,他引:7
通过研究地震远场前兆异常、超长期(8~20a)前兆异常和前兆异常判别上的差异,进一步揭示远场前兆异常的意义、前兆异常曲线的内涵和地震间的相互关联及地震预报的复杂性。该研究有助于进一步了解前兆异常的实质和深化地震预报。 相似文献
693.
EH4电磁成像系统在砂岩地区勘查地下水的应用研究 总被引:27,自引:2,他引:25
EH4电磁成像系统是1套电磁自动采集和处理系统,它是CSAMT和MT的结合体.本文介绍了EH4电磁成像系统的原理、特点和该系统在砂岩地区,如内蒙、新疆、云南等地区进行地下水勘查的应用实例和效果 相似文献
694.
明矾石综合利用的研究,有多种方法可供参考,通常是利用明矾石中的K、S、Al三种元素。碱熔法从明矾石中提Al的研究 从明矾石中提Al的物理工作参数和综合利用明矾石的方向。 相似文献
695.
696.
Flow failure of sandy subsoil induced by seismic liquefaction is known to cause significant damage to structures. It is induced not only by the dynamic forces exerted by seismic acceleration but also by the static gravity force in consequence of the topography of the ground. The ground flow may sometimes continue after the end of the seismic loading and finally the ground is significantly deformed to cause a failure.This paper numerically predicts the magnitude of flow that could occur when soil liquefaction continues for a sufficiently long period. It is considered that liquefied soil behaves like a viscous liquid, and hence, ground flow is governed by the principle of minimum potential energy. In the calculation, liquefied sand is assumed to be a viscous liquid that deforms in undrained conditions with its volume remaining constant. To consider the non-linearity due to large displacement, the updated Lagrangian method is used to solve the equation of motion. The Newmark β method is employed to calculate the time history of the ground motion. Finally, a simulation using this calculation method shows that the proposed method gives reasonable results for the conditions indicated. 相似文献
697.
In this paper, a study on the transient response of an elastic structure embedded in a homogeneous, isotropic and linearly elastic half-plane is presented. Transient dynamic and seismic forces are considered in the analysis. The numerical method employed is the coupled Finite-Element–Boundary-Element technique (FE–BE). The finite element method (FEM) is used for discretization of the near field and the boundary element method (BEM) is employed to model the semi-infinite far field. These two methods are coupled through equilibrium and compatibility conditions at the soil–structure interface. Effects of non-zero initial conditions due to the pre-dynamic loads and/or self-weight of the structure are included in the transient boundary element formulation. Hence, it is possible to analyse practical cases (such as dam–foundation systems) involving initial conditions due to the pre-seismic loads such as water pressure and self-weight of the dam. As an application of the proposed formulation, a gravity dam has been analysed and the results for different foundation stiffness are presented. The results of the analysis indicate the importance of including the foundation stiffness and thus the dam–foundation interaction. 相似文献
698.
The claim that there exists a transition of earthquake energy distribution between small and large earthquakes is checked using broadband radiated energy of earthquakes for global seismicity. Scattering of the relation between the magnitude and the broadband radiated energy makes it necessary to use the energy data directly. Rank-ordering statistics is applied to enhance the resolution in retrieving the power law distribution with undersampled data, namely, a few tens of events. Seen in the perspective of broadband radiated energy with higher resolution, there is no evidence for the kink in the frequency-energy distribution for large and small earthquakes. Instead, a single power law can well explain the data. For earthquakes with energy larger than 10~(14) J, we find that the number N of events with energy E depends on E via N ∝ E-B, with the scaling constant B = 0.64 ± 0.04, corresponding to b = 0.95± 0.06. 相似文献
699.
The Dansgaard-Oeschger event 4(DO4 event) is a significant warming event that occurred in the late Marine Isotope Stage 3. At present,there are different understandings about the detailed characteristics and internal structures of the DO4 event. Based on 6 precisely-dated 230Th ages and 188 oxygen isotope data of a stalagmite(No.XYⅢ-28)from the Xianyun Cave,Fujian Province,we present δ18O time series with an average resolution of 7 yr from 29.13 to 27.94 kyr B.P. Our new stalagmites δ18O records uncover the detailed processes of the DO4 event. The onset and end time of the DO4 event recorded by the stalagmite δ18O is 28.83±0.06 and 28.46±0.06 kyr B.P.,respectively, and the duration is 0.37±0.06 kyr. Differential with abrupt change of NGRIP ice core δ18O record at the onset of DO4 based on the GICC05 layer count time scale,the Xianyun Cave δ18O shows a relatively slow change. The Xianyun stalagmite δ18O values negatively shift by 0.4‰ within 145±60 yr,which indicates that the Xianyun Cave was likely affected by the ocean-atmosphere coupling of the tropical. In addition,the Xianyun stalagmite δ18O reveals a series of sub-million-scale summer monsoon enhancement events in and around the DO4 event,corresponding to the NGRIP ice core δ18O record and the Arabian Sea basin record. Our results suggest that the East Asian summer monsoon is related to the north-high latitude temperature and the ITCZ position changes on the sub-millennium-scale event. 相似文献
700.