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通过查看山西测震数字台网2009年1400个记录清晰事件波形,发现在ML<4.5的事件中有158次初至波前出现奇异小信号,在ML≤2.8的微小地震中小振幅波记录更加清晰。统计发现,这些小信号出现在使用GURALP公司生产的CMG-3ESPC地震计、CMG-DM24数据采集器的9个子台记录中,而其它型号的仪器系统中均未见。小信号主要集中在震中距<60km的近台记录初至前0.2～0.7s,经FFT分析,得出小信号频率集中在45～50Hz。认为该频率的信号在CMG仪器系统上有记录,主要是因为港震等其他类型的仪器系统可能将这部分频率成分过滤掉了,而它们恰好处在CMG仪器系统的记录范围内。
By observing the sharp event waveforms of 1400 records recorded by Shanxi Seismograph Network in 2009, it was found that there were 158 singular small signals before the first arrival wave in the case of ML <4.5, and clearer records of small amplitude waves in the small earthquakes with ML≤2.8 . Statistics show that these small signals appear in 9 sub-station records of the CMG-3ESPC seismometer manufactured by GURALP Corporation and the CMG-DM24 data collector, but not in other types of instrumentation systems. The small signals mainly concentrated in 0.2-0.7 seconds before the beginning of the epicenter recording of epicentral distances <60 km. The result of FFT analysis showed that the small signal frequency was concentrated in 45-50 Hz. The signal at this frequency is believed to be recorded on the CMG instrumentation system, mainly because other types of instrumentation systems such as the Hong Kong Earthquake may filter out this portion of the frequency content and they happen to be within the recording range of the CMG instrumentation system.