Time frequency domain polarization analysis of seismic waves in the whole space of mine and its experimental study

The propagation law of seismic waves under the condition of full space in coal mines is the key basic scientific problem of mine seismic exploration. The conventional methods are difficult to realize an accurate calculation of seismic waves direction because of the multi type waves field aliasing in the near field detection of the mine seismic method. The paper proposed a time frequency domain polarization analysis method of the three component seismic waves in coal mines. The time domain signals were converted into a time frequency domain signals by using the gener 〖LM〗alized S transform with the shape of the basic wavelet function with unfixed shape. The analytic signals were constructed by using the Hilbert transform and the complex covariance matrix were established at each time frequency point. The eigenvalues and eigenvectors of the complex covariance matrix were obtained,and then the polarization azimuth angle and polarization inclination angle of the three component signal were obtained. The experimental results of time frequency domain polarization analysis of the time domain aliasing synthetic signal show that the time frequency position of the calculated synthetic signal is corresponding to the theoretical time frequency position,and the calculated positive/negative azimuth angle and inclination angle have no error with the theoretical value. In the time and frequency dimensions,time frequency domain polarization analysis can accurately determine the polarization direction of multi type signals in the case of aliasing. The three dimensional high order three component simulation experiment of central excitation and omnidirectional reception in full space confirms that there is no deviation in the inclination angle and azimuth angle of the direct P wave and the S wave,and the azimuth deviation is small. According to the location and polarization information of the detection point,the central source is inversely positioned. In the range of 200 m diameter,the distance error between the focal point focalized according to the location of the detection point and the azimuth and dip angle of the seismic wave and the known focal point is only 0.548 6 m. The calculation of measured data in an underground coal mine verifies the effectiveness of the time frequency domain polarization analysis method of three component seismic waves in the whole space of the mine,which can provide a reference for underground seismic exploration in the whole space.