ANALYSIS OF TIME-FREQUENCY CHARACTERISTICS OF WAVE SPECTRUM BETWEEN TECTONIC EARTHQUAKE AND MINE EARTHQUAKE

There are many kinds of earthquakes in the Three Gorges area,such as tectonic earthquake,mine earthquake,reservoir induced seismicity and so on.And different earthquakes have different characteristics. But as far as this area is concerned,the majority of the earthquakes belong to micro-earthquakes and small earthquakes,so it is comparatively more difficult to identify their causes and types. The Three Gorges seismic network is a very good platform,which offers us very good earthquake data to do some research on the identification.In this paper,time-frequency spectrum method is used to analyze the difference between tectonic earthquake and mine earthquake,and this is the first step.By comparison,it is found there is obvious difference between them.Firstly,the main frequency of mine earthquake wave is lower than that of tectonic earthquake.And the main frequency of the former mainly centers around 2.2Hz,however the latter is around 5.5Hz.Secondly,the frequency component of tectonic earthquake wave is more abundant than that of mine earthquake,the former's energy density spectrum spreads more broadly along frequency and time axes,being 4 times broader than the latter. And it has many frequency segments with intense energy.Thirdly,the maximum value of energy intensity of mine earthquake wave occurs in all wave train earlier than that of tectonic earthquake and the energy decays quickly.