“…The performance of the conventional EI and FWI on the salt model in numerical experiments also verified this inference. Based on the above analysis, a new direct envelope Fréchet derivative was proposed (Chen, ; Chen & Wu, ; Chen, Wu, & Chen, , ; Chen, Wu, Wang, & Chen, ; Wu & Chen, , , ; Wu et al, ) to derive the sensitivity operator of the EI using the WAE where is the new envelope Fréchet derivative.…”