A Parallel Algorithm for Fresnel Tomography

In contrast with ray-based traveltime tomography, Fresnel tomography accounts for the band-limited nature of seismic waves and gives the higher resolution tomograms. Because Fresnel tomography demands much computer memory and much running time, a parallel algorithm for it is proposed. The tomographic inversion is transformed to resolving respectively a series of single equation in light of backprojection principle, each equation corresponding to a Fresnel zone. The forward and inverse computation concerning a Fresnel zone is allocated to one process and is independent of other processes. Then the storage and calculation of the large-scale matrix in the tomography are avoided. No message delivers between the slave processes, and only a little of data delivers between a master process and the slave ones. By using the portable message passing interface standard (MPI) for the communication, the computing code of the algorithm is implemented on Linux system, which allows to distribute the work on several PCs connected via standard Ethernet in an in-house network, and greatly expands the applicability of Fresnel tomography. The tests on the synthetic and observed seismic travel time data show that this parallel algorithm has a good performance on Linux PCs.