Depth and morphology of reflectors from the 2-D non-linear inversion of arrival-time and waveform semblance data: method and applications to synthetic data

Abstract

We propose a two-dimensional, non-linear method for the inversion of reflected/converted traveltimes and waveform semblance designed to obtain the location and morphology of seismic reflectors in a lateral heterogeneous medium and in any source-to-receiver acquisition lay-out. This method uses a scheme of non-linear optimisation for the determination of the interface parameters where the calculation of the traveltimes is carried out using a finite- difference solver of the Eikonal equation, assuming an a priori known back- ground velocity model. For the search of the optimal interface model, we have used a multiscale approach and the Genetic Algorithm global optimization technique. During the initial stages of inversion, we used the arrival times of the reflection phase to retrieve the interface model that is defined by a small num- ber of parameters. In the successive steps, the inversion is based on the opti- mization of the semblance value determined along the calculated traveltime curves. Errors in the final model parameters and the criteria for the choice of the bestfit model are also estimated from the shape of the semblance function in the model parameter space. The method is tested and validated on a synthe- tic dataset that simulates the acquisition of reflection data in a complex volca- nic structure.