Inversion-based Imaging: FWI beyond Velocity

Abstract

Summary Full waveform inversion (FWI) has been applied with great success to build velocity model, which is typically used in RTM or least squares reverse time migration (LSRTM) to produce high resolution images. With the fast advancements in the computer industry and the progress of the FWI algorithm, high resolution FWI has become common practices. Nevertheless, it is still computationally expensive to invert a velocity model that is directly interpretable using FWI. In this paper, we propose a unified approach for the inversion of velocity model and the image. Starting at lowest frequency possible that the input data support, FWI gradually moves to higher frequencies, which allows it to invert a broad band velocity model. A reflectivity model is then computed directly from a velocity model inverted from FWI without the need of migration as it is in a typical workflow. Numerical examples show that the reflectivity image derived from a 15 HZ FWI velocity model have better resolution and improved continuity compared to the images from RTM and LSRTM. These benefits partially come from the contribution of both refraction and reflection energy used in FWI.