中文摘要：

汶川地震前，我国及周边地区地震台站记录的地脉动信号显著增强，对这段时期内的地脉动信号进行频谱分析发现，它们的能量主要集中在0．20Hz附近．通过单台法对该频段信号进行定向，发现多个大陆和海岛台站记录的地脉动信号来源方向均指向我国东部海域，且方向变化与同期的威马逊台风路径保持很好的一致性．结合已有的地脉动信号强度随与台风中心距离增加而衰减的研究，我们认为汶川地震前的地脉动信号增强是由台风引起，而不是汶川地震的前兆．

英文摘要：

Enhancement of microseisms was observed at many stations in China and adjacent areas just before the Wenchuan Earthquake of 2008. Spectrum analysis shows that the dominant frequency of this signal is around 0.20 Hz. The polarization method was employed to locate the source of such signals at continent and island stations. We found that the signals of all stations are directed to the East China Sea and their variations correspond to the path of the Ramasun typhoon well Considering previous research about the relationship between microseisms amplitude and distances from stations to the center of the Ramasun typhoon, we suggest that the enhancement of microseisms before the Wenchuan earthquake was caused by the Ramasun typhoon, rather than the precursor of the Wenchuan earthquake proper.