In this paper, the time series of geoelectrical resistivity, geomagnetism, earth deformation and gravity are processed with fast Fourier transform method, "FFT" for short. There are three main harmonics in daily mean data of the earth resistivity, recorded at Baochang and Wujiahe seismic stations. The harmonic with a period of approximately one year, has physical meaning. Different items in same geomagnetic station or same items in different geomagnetic stations, usually contain four main harmonics whose periods are 24, 12, 8 and 6 hours. Besides there exist tidal waves, there are different harmonics in the minute values recorded by horizontal pendulum tiltometer, water tube inclinometer, and gravimeter. It can be effective measuring the periods of noise precisely using FFT. But there are still many jobs to do in future, for example improving methods, the selection of data, explaining physical meaning of harmonic, etc.%利用FFT方法,对地电、地磁、形变及重力等前兆时间序列信号进行分析,结果显示,宝昌地震台及乌加河地震台地电两测向日均值时间序列存在3个主要谐波分量,其中周期近一年的分量物理意义明确.FFT方法在精确确定前兆时间序列中的干扰信息周期时具有较好的效果.
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