Accurate Determination Of P-Wave Backazimuth And Slowness Parameters By Sparsity-Constrained Seismic Array Analysis

Based on seismic array, the conventional frequency-wavenumber method, or the FK method, is generally used to determine the backazimuth and slowness parameters for the plane wave arriving at the seismic array. However, at low frequencies the FK method results in low-resolution estimation of both parameters. To overcome this issue, we have developed a new seismic array analysis method based on sparsity-constrained (SC) inversion to better determine the backazimuth and slowness parameters. The SC method takes advantage of the sparsity of the incoming wave front in the domain of slowness and backazimuth. We have tested the proposed SC method using synthetic data calculated for Shanghai Earthquake Agency Array (SEAA) from one single source and two sources, respectively. Compared to the FK method, the proposed SC method has a much higher resolution in estimating the backazimuth and slowness parameters. Furthermore, the SC method can more easily separate multiple sources and estimate the two parameters. We also compare the proposed SC method with another advanced seismic array analysis method CLEAN-PSF, which can find the position and strength of point sources. Overall, our proposed SC method performs better than or at least at the comparable level as the CLEAN-PSF method. We further demonstrate the effectiveness of the new method on the 2008 M-w 8.0 Wenchuan earthquake data recorded on the SEAA. The deviation between theoretic backazimuth and optimal solution is approximately 4 degrees , indicating the capability of the proposed SC method for reliably estimating the backazimuth of teleseismic event based on a seismic array.