汶川震前几种低频事件波形分析

Analysis on a few kinds of low frequency events and their waveforms before Wenchuan earthquake

列举分析了国外文献所记载的几类低频事件.选择汶川MS8.0地震主断层附近四川省部分台网宽频带数据,采用相应频段,进行带通滤波处理,检测到4种类似的低频事件波形.分别为低频震颤与滑移事件(ETS事件),深低频地震事件(LFE事件),深低频震动事件(DLF事件),以及超低频震动事件(VLF事件).定位分析实例证实,汶川震前的ETS和DLF等低频事件发生在主断层附近,表明大震发生之前龙门山断裂带附近有低频事件发生,主要为ETS和VLF两类事件及少量DLF事件.因有远震记录与LFE事件时间相近,无法确认此类事件是否存在.低频事件作为天然地震目录的补充,可为大震前兆和触发机理研究提供新的探索方向.

This paper lists and analyzes a few kinds of low frequency events studied in foreign literature. By choosing broadband records at stations of Sichuan digital seismic network near main fault of the Wenchuan earthquake and band filtering these datum, we detected four similar low frequency events, i. e. , episodic tremor and slip events （ETS）, low frequency events （LFE）, deep low frequency events （DLF） and very low frequency events （VLF）. Located ex- amples confirm that several low frequency events occurred near the Longmen-shan fault, most of them are ETS and VLF and minority is DLF. We can not verify whether LFE events actually exist or not~ because there are distant earth- quakes at the same time. As a supplement to traditional earthquake catalog, low frequency events may provide us a new research line for exploring possible pre- cursors and triggering mechanism of strong earthquakes.