DSurfTomo is a surface wave inversion program which can directly invert surface wave dispersion data to 3D shear wave speed without the intermediate step of constructing the phase or group velocity maps. The fast marching method (FMM) (Rawlinson et al., 2004) is used to compute, at each period, surface wave travel times and ray paths between sources and receivers. This avoids the assumption of great-circle propagation that is used in most surface wave tomographic studies, but which is not appropriate in complex media. Please refer to Fang et al. (2015 , GJI) for the detail description of the method.

Fang, H., Yao, H., Zhang, H., Huang, Y. C., & van der Hilst, R. D. (2015). Direct inversion of surface wave dispersion for three-dimensional shallow crustal structure based on ray tracing: methodology and application. Geophysical Journal International, 201(3), 1251-1263. Rawlinson, N. & Sambridge, M., 2004. Wave front evolution in strongly heterogeneous layered media using the fast marching method, Geophys. J. Int., 156(3), 631–647