“…In that case, the manually driven 'migrate-pick-flood' approach remains a preferable, albeit erroneous, industrial solution to build the velocity model. However, several FWI studies based on the level-set method (Lewis et al, 2012;Kadu et al, 2017), novel objective functions (Yang and Engquist, 2017;Wu and Chen, 2018), model regularization (Esser et al, 2016;Brandsberg-Dahl et al, 2017) and so on, have been proposed in recent years as an alternative to the above mentioned industrial ad-hoc practice. Towards that aim, this article extends the idea proposed in Kalita et al (2018a,b) to a 3-D regime.…”