Rapid Method for Acoustic Wave‐Equation WTW Inversion of Crosshole Seismic Data

Abstract

AbstractWTW is a hybrid inversion method of wave‐equation traveltime inversion (WT) and waveform inversion. Wave function is used to calculate the traveltime and derivative (perturbation of traveltime with respect to velocity) in WT. Unlike traditional ray‐based travetime inversion, WT has many advantages. No ray tracing or traveltime picking and no high frequency assumption is necessary and good result can be got while starting model is far from real model. Comparing with waveform inversion, WT has low resolution. Complementary to WT, waveform inversion has high resolution, but easily sticks in local minima when starting model is far from real model. So WTW is a good hybrid inversion method. Traditional WTW is to first reconstruct the smooth characters of model with WT inversion being primary and then reconstruct the detailed characters of model with waveform inversion being primary. But the computation time and memory using of this method are twice of that of WT inversion or waveform inversion. So a simplified method is used actually. That is to first use WT singly and then waveform inversion singly. Advantages and disadvantages of two inverse methods are not sufficiently complement for iterations with simplified method, this affects the inverse result. This paper proposes a new method to implement WTW and computation time and memory using are same with that of WT or waveform inversion. Model calculation shows the new method has better convergence.