background velocity meaning in English

背景速度

A hybrid migration method , named " fourier finite - difference migration " , is a post - stack depth migration scheme . the downward extrapolation operator is split into three operators : one operator is a phase - shift operator for a chosen constant background velocity , another operator is the well - known first - order correction term , and the third operator is a finite - difference operator for the varying of the velocity function . phase - shift downward extrapolation and finite - difference downward extrapolation preserves the advantage of phase - shift method and finite - difference method
傅立叶有限差分(简称ffd )偏移算法是一种叠后深度偏移算法，其向下延拓算子是一种混合算子，包括三项：一项是处理常速的相移算子，一项是一阶相移修正算子，最后一项是类似45度方程的有限差分算子，用来处理剧烈横向变速。