Based on the Ms≥6.0 strong earthquake records since fourth seismic active period in North China area,a probability statistical model for the occurrence of strong earthquake(over 6.0) in seismic active period is presented.Tested with 3 mathematical methods,it shows that the model is credible.

The power spectra and autocorrelation function of the ground microtremor records in Zhangjiakou and Xinglong Seismostation are calculated. The results show that there are 4 peak values in the microtremor spectra of Xinglong Seismostation (0.3Hz, 3Hz, 8Hz,15Hz) and 3 peak values in Zhangjiakou Seismostation (0.3Hz, 3Hz, and 15Hz). The autocorrelation function in the UD direction of Xinglong station showed a typical red noise shape, but its EW direction showed negative correlation, which may be the affection of slantwise pulsation that acts on only in horizontal direction. Small instrumental interference signal is hard to distinguish, whether is from pulse calibration or seismic waves, but it is easy in spectral analysis of ground microtremor. The predominant cycle of ground microtremor in the two stations, which concentrated basically in 0.3s, was relatively stable.

利用昌黎、红山等台站的地磁Z分量日变资料,分析了磁静日幅度、磁扰日幅度和磁静日低点时间的年变化与长期变化,结果年变化和长期变化都非常明显.磁静日幅度的长期变化量可达14～15 nT;磁静日低点时间的年变化,提前区与滞后区低点时间最大可相差42 min.而低点时间的长期变幅度化幅度一般50 min左右,且长期变化量由西向东有逐渐减小趋势,最大与最小两台时差可达21 min.长期变幅最小的2个台为文安和昌黎,可能与海水影响有关.