Non-linear orthorhombic AVAZ inversion workflow

In this paper, we present an amplitude variation with azimuth (AVAZ) non-linear orthorhombic inversion workflow. The workflow integrates an inversion based on linearized orthorhombic PP-reflectivity equations and an inversion based on non-linear general Zoeppritz equations. The former is suitable for weak contrasts and the latter valid also for strong interfaces. The strong-contrast orthorhombic AVAZ inversion uses a quasi-Newton solver. Quasi-Newton methods find local minima and, as such, are dependent on the starting model supplied. To provide a good initial model for the non-linear inversion, we propose a workflow that uses the linearized solution. We describe the workflow and demonstrate it on a synthetic example.