We have investigated a method of inverting amplitudes of both PP and converted PS prestack data to three parameters -- P- and S-wave impedance, plus density. Results from 3-parameter joint inversion are compared with those from 2-parameter joint inversion, which uses only P- and S-wave impedance data. The inversion program performs an AVO inversion using a singular value decomposition (SVD) method. The advantage of the SVD method over the more commonly used least-squares method lies in working with matrices that are either singular or else numerically very close to singular. To investigate the contribution of incorporating both PP and PS data in joint inversion, 3- parameter joint-inversion results are compared to those from PP- and PS-only inversions. To reduce the computation cost of prestack migration (used for improving lateral resolution and correlating PP and PS data in depth), the input datasets are arranged in limited-offset stack sections. Using only a small number of limited-offset stack traces as input to the inversion program produces results as good as using all offset traces.
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