Efficient line search methods for multi-parameter full wavefield inversion

Abstract

Method for simultaneously inverting full-wavefield seismic data () for multiple classes of physical property parameters (e.g., velocity and anisotropy) by computing the gradient (), i.e. search direction (), of an objective function for each class of parameters, then applying (preferably exhaustive) first-pass independent line searches to each parameter class to obtain the corresponding step size () along the search direction for each parameter class; then without yet updating the model, using the step sizes to define a relative scaling between gradients of all parameter classes. Next, each scaled search direction is recombined to form a new search direction (), and a new second-pass line search is performed along the new search direction (), and all parameters are simultaneously updated with the resulting step size (). Alternatively to the preceding alternating two-pass embodiment, the model may be updated after each first-pass line search, and no second-pass line search is performed.