汶川大震前数字地震仪位移地脉动低频异常现象研究

Research on Low-frequency Anomalies of Microtremor Displacement Recorded by Digital Seismigraph before the Whenchuan Earthquake

摘要:

选取了2008年4月25日至5月12日间的四川台网14个台宽频带地震仪记录到的地脉动波形资料,把速度波形做适当的数据校正和滤波处理后,经积分转换成位移波形。频谱分析结果表明:地震发生前存在低频异常颤动,地震前2～3天开始0.1～0.3Hz频段傅里叶谱幅值逐渐增大;各个台的位移振幅值逐渐增强。其中靠近龙门山断裂带的台站记录到的地脉动变化较明显。

Abstract:

Through selection the broadband digital seismic data from April 25,2008 to May 12, 2008, recorded by fourteen seismic stations in Sichuan province, the microtremor wave form records are transformed to displacement wave forms after the data correction and filtering. The results of Fourier analysis indicate that before the earthquake occurred the low-frequency abnormal quiver is found; Fourier spectrum value at 0. 1 -0.3 Hz band is increased in two to three days. Amplitude values of displacement waves are gradually increased at every seismic stations. The microtremor records change greater at stations near the Longmenshan fault zone.