MECHANISM OF ZIGZAG DISPERSION CURVES IN RAYLEIGH EXPLORATION AND ITS INVERSION STUDY
ZHANG BI-XING;XIAO BO-XUN;YANG WEN-JIE;CAO SI-YUAN; MOU YONG-GUANG (1) Institute of Acoustics, Chinese Academy of Sciences, Beijing 100080, China; 2) Changjiang Engineering Geophysical Prospecting Institute, Changjiang Water Resource Committee,Wuhan 43001
The mechanism of zigzag dispersion curves in the Rayleigh wave exploration is theoretically analyzed. The propagation characteristics and interrelation of the guided waves are studied thoroughly. It is presented that the zigzag stature of Rayleigh wave dispersion curves is the result of many modes generated by the low-velocity layers or fractures in multilayered. The inverse problems are also investigated on the formation structure with the dispersion curves of the Rayleigh wave by the damping method of least squares and the genetic algorithm. It is found that the damping method of least squares is not suitable to the inversion of zigzag dispersion problem of Rayleigh wave, while the genetic algorithm is a good method for this problem.