“…One-way approximation for wave propagation has been introduced and widely used as propagators in forward and inverse problems of scalar, acoustic and elastic waves (e.g., Claerbout, 1970Claerbout, , 1976Landers and Claerbout, 1972;Flatté and Tappert, 1975;Corones, 1975;Tappert, 1977;McCoy, 1977;Hudson, 1980;Ma, 1982;Wales and McCoy, 1983;McCoy, 1984, 1985;Wales, 1986;McCoy and Frazer, 1986;Collins, 1989Collins, , 1993Collins and Westwood, 1991;Stoffa et al, 1990;Fisk and McCartor, 1991;Wu and Huang, 1992;Ristow and Ruhl, 1994;Wu, 1994Wu, , 1996Wu, , 2003Wu and Xie, 1994;Huang and Wu, 1996;Wu and Jin, 1997;Grimbergen et al, 1998;Van Stralen et al, 1998;Wild and Hudson, 1998;Huang et al, 1999aHuang et al, , 1999bThomson, 1999Thomson, , 2005De Hoop et al, 2000;Lee et al, 2000;Wild et al, 2000;Wu et al, 2000aWu et al, , 2000bLe Rousseau and De Hoop, 2001;Wu, 2001, 2006;Wu, 2001, 2005;…”