Test for comparison of array layout in natural source surface wave exploration

In order to select the array layout with high efficiency and convenience for surface wave exploration using natural sources, four tests for data acquisition with different layout are carried out in the same field. Then we perform comparative analysis of the dispersion curves extracted by using SPAC and ESPAC for different array layout. And then the velocity structure of the shallow layer is obtained by inversion. Test results show that the dispersion curves extracted from the four arrays are very similar, and spectrum energy in the frequency domain is more concentrated for the nested equilateral triangle and circular arrays than that for the linear and L-shape arrays. The dispersion curve extracted from the L-shape array is better than the linear array in the high frequency band (8—40 Hz), while worse in the low frequency band (4—8 Hz). Since worse dispersion appears at high frequencies for the linear array, a joint exploration with both artificial and natural sources is proposed. The test result proves that the joint method can not only improve the quality of dispersion curve in the high frequency band to ensure the reliability of the detection precision, but also achieve dispersion data in a much broader frequency range. Consequently both shallow and deeper structure can be obtained in the inversion.