PRELIMINARY ANALYSIS TO THE SIGNALS OF GROUND MICROTREMOR IN ZHANGJIAKOU AND XINGLONG SEISMOSTATION

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.