JOINT P-WAVE AND S-WAVE VELOCITY DETERMINATION FROM REFLECTED PP, SS AND CONVERTED PS SP PHASES FROM LARGE-APERTURE SEISMIC-REFLECTION MEASUREMENTS/

As less aliased (better sampled) seismic studies are acquired more SS reflections and especially PS/ SP converted phases are recognized. We use a synthetic (tau, p) data set to demonstrate the viability of usin g PP, SS reflections and PS/SP conversions in a joint inversion scheme to obtain average, one-dimensional P- and S-wave velocity models. We achieve a coupling between the P- and S-wave velocity-depth functions by introducing all these wave types in a single joint inversion. The n ew information introduced by the converted phases provides additional constraints, and better resolved velocity-depth models can be estimate d. In our synthetic data case the resolution kernels become sharper, d ecreasing the width of the main lobe by 10-50% and increasing their he ight by 20-40%. This increase in resolution can result in a significan t decrease in the uncertainty estimates of Poisson's ratios. In our sy nthetic test the uncertainties decrease approximately 50%. We use this inversion scheme to invert (tau, p) sections from horizontal componen ts recorded in a seismic experiment along the southwest coast of Green land. The joint inversion results resolve different levels of anisotro py within the crust. These anisotropic fabrics can be responsible for the time difference (delay) between the radial and transverse (tau, p) sections, that causes a decrease in the amplitude of the S-wave field when the two (tau, p) sections (radial and transverse) are stacked.