Abstract: By using the methods of the power spectral analysis and Sompi spectral analysis, the authors have studied the short-period microseism waveform and some special wave­forms before some large earthquakes ,and the results show that: before larger earthquakes, the peak frequency,corner frequency,relative width of frequency domain,relative value of peak spectrum, the absolute slope value of high frequencies and Sompi spectral frequency may decrease (some may increase). So,some of them may be used as an important index for earthquake prediction.

Key words: Microcrack Microseisms, Special waveform, Power spectral analysis, Sompi spectral analysis