The lithospheric magnetic field （LMF） in China and its surrounding are calculated using the spherical har- monic coefficients given by the NGDC-720 model. The LMF comes from the magnetization of minerals in the crus...The lithospheric magnetic field （LMF） in China and its surrounding are calculated using the spherical har- monic coefficients given by the NGDC-720 model. The LMF comes from the magnetization of minerals in the crust and in the uppermost mantle. It may, therefore, provide unique insight into lithospheric tectonic processes and mechanisms. Here, we study the geomagnetic manifesta- tion of active tectonic blocks, and find a close correlation between the LMF and seismicity. Many large faults are found to closely overlap with magnetic anomalies, or are distributed along the boundaries of magnetic anomalies. Earthquakes in these fault regions have occurred on the boundaries of magnetic anomalies, or in the transition zones between posilive and negative anomalies. We ana- lyze the components of the LMF, and the LMFs at different altitudes, finding that the vertical component, Bz at 200 kin, is the most related to seismic activity. Relevant physical mechanisms are also discussed. We propose that the stress or viscosity differences caused by temperature variations, which manifest in the LMF, may be the pre- dominant reason for the correlation between the LMF and seismic activity along large faults.展开更多
On the basis of the authors’ experiences of setting up an NGDC Web site,this paper attempts to present some significant aspects about the security of NGDC based on ASP.They include data storing,database maintenance,n...On the basis of the authors’ experiences of setting up an NGDC Web site,this paper attempts to present some significant aspects about the security of NGDC based on ASP.They include data storing,database maintenance,new technical support and so on.Firstly,this paper discusses how to provide the security of data which is saved in the hosts of NGDC.The security model of "Networks_DB Server_DB_DB Object" is also presented.In Windows NT Server,Internet Information Server (i.e.,IIS) is in charge of transferring message and the management of Web sites.ASP is also based on IIS.The advantages of virtual directory technique provided by IIS are emphasized. An NGDC Web site,at the Research Center of GIS in Wuhan Technical University of Surveying and Mapping is also mentioned in this paper.Because it is only an analoge used for case study,the transmission of digital spatial products is not included in the functions in this NGDC Web site.However,the management of spatial metadata is more important and some functions of metadata query are implemented in it.It is illustrated clearly in the functional diagram of the NGDC Web site.展开更多
针对国内对高精度增强地磁场模型(enhanced magnetic model,EMM)在基于球谐分析时对阶数存在认知偏差、实现模型的软件研究较少以及计算精度不高等问题,考虑了地磁场7要素的关系,建立了基于球谐分析740阶次的EMM模型,给出了Schmidt半标...针对国内对高精度增强地磁场模型(enhanced magnetic model,EMM)在基于球谐分析时对阶数存在认知偏差、实现模型的软件研究较少以及计算精度不高等问题,考虑了地磁场7要素的关系,建立了基于球谐分析740阶次的EMM模型,给出了Schmidt半标准化缔合勒让德函数,给出了EMM模型的计算步骤,并用MATLAB实现EMM2015模型(2000~2019年)在地球上任意地磁场7要素的计算和等值线图的绘制,将计算值与美国国家海洋和大气管理局公布模型的运行数据进行误差对比分析,各元素的均方根偏差最大为0.86 nT或0.4′,比720阶的EMM模型的精度提高了3倍。结果表明,提供的EMM2015模型软件实现方法具有较高的计算精度,值得推广和应用。展开更多
基金funded by the Seismic Industry-Specific (201108004)Liguo Jiao is also supported by the Central Research Institutes of Basic Research and Public Service Special at Institute of Geophysics, China Earthquake Administration (DQJB11B13)National Nature Science Foundation of China (41174056,41274079)
文摘The lithospheric magnetic field （LMF） in China and its surrounding are calculated using the spherical har- monic coefficients given by the NGDC-720 model. The LMF comes from the magnetization of minerals in the crust and in the uppermost mantle. It may, therefore, provide unique insight into lithospheric tectonic processes and mechanisms. Here, we study the geomagnetic manifesta- tion of active tectonic blocks, and find a close correlation between the LMF and seismicity. Many large faults are found to closely overlap with magnetic anomalies, or are distributed along the boundaries of magnetic anomalies. Earthquakes in these fault regions have occurred on the boundaries of magnetic anomalies, or in the transition zones between posilive and negative anomalies. We ana- lyze the components of the LMF, and the LMFs at different altitudes, finding that the vertical component, Bz at 200 kin, is the most related to seismic activity. Relevant physical mechanisms are also discussed. We propose that the stress or viscosity differences caused by temperature variations, which manifest in the LMF, may be the pre- dominant reason for the correlation between the LMF and seismic activity along large faults.
文摘On the basis of the authors’ experiences of setting up an NGDC Web site,this paper attempts to present some significant aspects about the security of NGDC based on ASP.They include data storing,database maintenance,new technical support and so on.Firstly,this paper discusses how to provide the security of data which is saved in the hosts of NGDC.The security model of "Networks_DB Server_DB_DB Object" is also presented.In Windows NT Server,Internet Information Server (i.e.,IIS) is in charge of transferring message and the management of Web sites.ASP is also based on IIS.The advantages of virtual directory technique provided by IIS are emphasized. An NGDC Web site,at the Research Center of GIS in Wuhan Technical University of Surveying and Mapping is also mentioned in this paper.Because it is only an analoge used for case study,the transmission of digital spatial products is not included in the functions in this NGDC Web site.However,the management of spatial metadata is more important and some functions of metadata query are implemented in it.It is illustrated clearly in the functional diagram of the NGDC Web site.
文摘针对国内对高精度增强地磁场模型(enhanced magnetic model,EMM)在基于球谐分析时对阶数存在认知偏差、实现模型的软件研究较少以及计算精度不高等问题,考虑了地磁场7要素的关系,建立了基于球谐分析740阶次的EMM模型,给出了Schmidt半标准化缔合勒让德函数,给出了EMM模型的计算步骤,并用MATLAB实现EMM2015模型(2000~2019年)在地球上任意地磁场7要素的计算和等值线图的绘制,将计算值与美国国家海洋和大气管理局公布模型的运行数据进行误差对比分析,各元素的均方根偏差最大为0.86 nT或0.4′,比720阶的EMM模型的精度提高了3倍。结果表明,提供的EMM2015模型软件实现方法具有较高的计算精度,值得推广和应用。
