【摘要】 <正> 引言 1967年J. P. Burg提出了最大熵法(MEM),亦称最大熵谱法,1971年、1972年Lacoss和Burg等人分别讨论了该方法的数学特征,并发现该方法优越于快速傅里叶变换。MEM的分辨率是一般谱分析的4倍,尤其是对于短资料的谱分析可得到更真实的谱估值。1972年T. J. Ulrych将此方法用于地磁资料的分析中,并采用了最终预报误差(FPE)的定阶方法确定滤波系数的阶。1974年N. Andersen提出了适合于计算机处理的MEM滤波系数的递推算法框图,可快速简便地进行谱分析。MEM方法在气象更多还原

【Abstract】 It is generally accepted that the plane distributions of earthquakes in the third and fourth seismic cycles (1480-1740; 1800-1983) in North China are different. However, there have been few studies on the temporal distributions of the earthquakes during both cycles. The maximum entropy spectral method with high resolution and less deviated peak values is used to analyse the relationships between the seismicities and the drought-waterlogging data obtained from 24 meteorological observatories during the third and fourth seismic cycles in North China. The results show that the main phases for both seismicity and drought-waterlogging during the third cycle are 21 years, 10 years, and 21 years, 10.2 years respectively; and the phases for both of them during the fourth cycle are 13.8 years, 7.7 years, and 12 years, 7.4 years separately. These two phases are not only consistent with each other, but also in conformity with the mean period of 22 years for solarspot activity, and with the variational periods of 13.15 years and 7 years for the earth rotations. It is indicated that the seismic activities and the climate changes appear to be related to the variations of the solar activity and the earth rotation. Such shortening of periods merit further considerations in searching for the dynamic forces of earthquakes and in assessing the seismic potential.更多还原