Fresnel volume tomography based on the first arrival of the seismic wave
初至波菲涅尔体地震层析成像

According to the finite-frequency theory, for a single source-receiver pair, not only the points on the raypath but also those outside the ray affect the wave propagation. This kind of effect can be described by sensitivity kernel. On the basis of the Born and Rytov approximations, we derive the amplitude and traveltime sensitivity kernels for Fresnel volume tomography corresponding to different dimensions in heterogeneous medium. The analytical expressions of the sensitivity kernels in homogeneous media are presented, through which we give the distribution ranges of the amplitude and traveltime sensivitity kernels under different dimensions. Furthermore, we present the calculation methods of band-limited sensitivity kernels and the corresponding distribution ranges. According to the first arrival information of the seismic wave, we apply Fresnel volume tomography to the inversion of the near surface velocity of the earth. The inversion results of the theoretical model and practical data indicate that first arrival Fresnel volume tomography has the advantage of higher accuracy than the conventional raypath tomography.