Estimation of false amplitude anomalies on seismics from Ocean Bottom acquisition (OBS/OBC) from converted waves in 3D anisotropic models

Ideally, a seismic data cube should contain amplitudes that are proportional to the reflectivity of the subsurface. In practice, the seismic amplitudes used for interpretation are highly dependent on other factors such as survey geometry, instrumentation, filtering and muting of prestack data, migration artifacts, focusing/defocusing and wave attenuation in the overburden, and several other factors. When an amplitude variation is encountered in the seismic data, it is not easy to separate these factors fr om the searched-for reflectivity. For sea bottom seismics with converted rays in anisotropic models, it becomes even more complicated to separate the reflectivity from the other factors due to the complex behaviour of P-waves and in particular S-waves in anisotropic media. The objective of this project is to predict “false” amplitude anomalies from interpreted target horizons in real seismic OBC (Ocean Bottom Cable) or OBS (Ocean Bottom Sensor) data for elastic waves in 3D anisotropic models with emphasi s of converted waves. This will be done by applying the Simulated Migration Amplitude (SMA) method with synthetic seismic traces from the anisotropic wavefront construction algorithm that will be developed as a part of the project. Most rocks have anisot ropic properties which affect in particular the S-waves, but also to some extent the P-waves. The result of the project will be SMA maps that quantify the summed effects of the unwanted factors (survey geometry, instrumentation, filtering and muting etc ...) across any target surface in depth. Together with the real amplitude map, the SMA map can be used to make better predictions of lithology.