In this paper, we use the daily ranges of the vertical magnetic intensity of approximately 76 geomagnetic stations from January 1, 2008 to December 31, 2010 to analyze the spatial and temporal characteristics of Z ran...In this paper, we use the daily ranges of the vertical magnetic intensity of approximately 76 geomagnetic stations from January 1, 2008 to December 31, 2010 to analyze the spatial and temporal characteristics of Z ranges. The results are summarized as follows: (1) Temporally, we use regressive analysis and FFT analysis to analyze the data. The results show that the Z component daily ranges of all stations have an obvious cyclical variation, the computed Fourier spectra of all data sets have clearly resolved the required periodicities in the data, in the form of distinct peaks at days 365, 183, 22, and 73, and the power spectra of day 365 is the highest in all periods. (2) In terms of spatial variation, the daily ranges show nonlinear variation with latitude in China. The results show the existence of a point of inflexion (maximal value point) nearby at about 25°N, the daily ranges of Z rise from 15°~25°N and have a good linear decrease variation along with 25°~50°N. (3) Compared with the spatial and temporal variations of Z daily ranges with the Sq current inversion, we found that the spatial and temporal characteristics of Z ranges are decided mainly by the spatio-temporal evolution of the Sq current system. (4) If the latitudes of the maximum amplitudes of variation of the vertical component in the geomagnetic quiet days are roughly taken as the latitudes corresponding to the foci of Sq overhead current system, we can see that these latitudes of foci become higher in summer, are lowest in winter and highest during Equinoxes, displaying conspicuous monthly and daily variations. For two successive geomagnetic quiet days, the latitudes of foci may vary ten degrees.展开更多
Taking the northeast seismic zone as an example and based on the magnitude-frequency distribution principles of the G-R relationship and the study on the temporal and spatial distribution characteristics of the minimu...Taking the northeast seismic zone as an example and based on the magnitude-frequency distribution principles of the G-R relationship and the study on the temporal and spatial distribution characteristics of the minimum magnitude of completeness M C in each time interval,this paper makes a statistical analysis on the seismicity parameters of the research area and explores the influence of the completeness of small earthquake data on the seismicity parameters and seismic hazard analysis.It shows that the completeness analysis of the regional small earthquakes data provides a possible means for obtaining more accurate seismicity parameters that can better represent the actual regional seismicity level for areas of low seismicity.The research methods of this article and its conclusion can be used as a reference for the completeness analysis of earthquake data and seismic activity research.展开更多
基金supported by the special fundamental research fund of Institute of Geophysics,CEA for Central Public Welfare Research Institutes(DQJB11C10)the fund for the Task of Tracing Earthquake Trend of China Earthquake Administration(Grant No.2010020705)
文摘In this paper, we use the daily ranges of the vertical magnetic intensity of approximately 76 geomagnetic stations from January 1, 2008 to December 31, 2010 to analyze the spatial and temporal characteristics of Z ranges. The results are summarized as follows: (1) Temporally, we use regressive analysis and FFT analysis to analyze the data. The results show that the Z component daily ranges of all stations have an obvious cyclical variation, the computed Fourier spectra of all data sets have clearly resolved the required periodicities in the data, in the form of distinct peaks at days 365, 183, 22, and 73, and the power spectra of day 365 is the highest in all periods. (2) In terms of spatial variation, the daily ranges show nonlinear variation with latitude in China. The results show the existence of a point of inflexion (maximal value point) nearby at about 25°N, the daily ranges of Z rise from 15°~25°N and have a good linear decrease variation along with 25°~50°N. (3) Compared with the spatial and temporal variations of Z daily ranges with the Sq current inversion, we found that the spatial and temporal characteristics of Z ranges are decided mainly by the spatio-temporal evolution of the Sq current system. (4) If the latitudes of the maximum amplitudes of variation of the vertical component in the geomagnetic quiet days are roughly taken as the latitudes corresponding to the foci of Sq overhead current system, we can see that these latitudes of foci become higher in summer, are lowest in winter and highest during Equinoxes, displaying conspicuous monthly and daily variations. For two successive geomagnetic quiet days, the latitudes of foci may vary ten degrees.
基金Fund for the research was granted from Institute of Crustal Dynamics,China Earthquake Administration(No.ZDJ2013-05)and(No.ZDJ2010-20)
文摘Taking the northeast seismic zone as an example and based on the magnitude-frequency distribution principles of the G-R relationship and the study on the temporal and spatial distribution characteristics of the minimum magnitude of completeness M C in each time interval,this paper makes a statistical analysis on the seismicity parameters of the research area and explores the influence of the completeness of small earthquake data on the seismicity parameters and seismic hazard analysis.It shows that the completeness analysis of the regional small earthquakes data provides a possible means for obtaining more accurate seismicity parameters that can better represent the actual regional seismicity level for areas of low seismicity.The research methods of this article and its conclusion can be used as a reference for the completeness analysis of earthquake data and seismic activity research.
