Wave-equation first-arrival tomography for 3-D near-surface velocity inversion

Summary In wave-equation traveltime inversion, the major computation comes from the calculation of the functional gradient or Frechet derivative. Considering that the goal of traveltime inversion is to recover the large-scale velocity model (i.e., the low-wavenumber component), we propose a computationally economical method to calculate the functional gradient using the monochromatic traveltime sensitivity kernel, which considerably reduces the computational cost as well as memory requirement. 3-D field test demonstrates that a high-resolution near-surface velocity model can be inverted using wave-equation traveltime tomography with affordable computer resources.