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

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 examples confirm that several low frequency events occurred near the Longmenshan 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 earthquakes at the same time. As a supplement to traditional earthquake catalog，low frequency events may provide us a new research line for exploring possible precursors and triggering mechanism of strong earthquakes.