Publications

A tomographic inversion approach using prestack depth migrated common image gathers is utilized to compensate reflection data for amplitude loss caused by transmission anomalies, such as shallow gas, in the overburden. The approach has the advantage of estimating transmission losses from anywhere within the overburden using the actual seismic raypaths. It includes the following procedures: (1) picking events on the CIGs, measuring their amplitudes and estimating the dip fields on the migrated stacked volume, (2) defining a represented model and updating the amplitude perturbations in the model through tomographic inversion, (3) using raytracing to calculate the cumulative amplitude scaling factors from the perturbations and scale up the prestack migrated data accordingly. Examples show that the method can mitigate amplitude attenuation caused by transmission anomalies and should be considered as one of the processes for amplitude preserving processing that is important for AVO analysis when transmission anomalies are present.