MULTICHANNEL SEISMIC DATA ACQUIRED RECENTLY OVER SHATSKY RISE

Multichannel seismic data acquired recently over Shatsky Rise in the NW pacific have the potential to provide important constraints on structure and rock properties from this oceanic plateau. We apply a reversible jump Markov Chain Monte Carlo (rjMCMC) sampling technique to invert for acoustic impedance structure from portions of the processed, post-stack seismic lines. This approach, which applies a Bayesian inversion formulation, also allows a quantification of uncertainty in inversion results. It also allows an automatic estimation of the number of model parameters, such as the number of layers, required to fit the data, greatly simplifying the inversion. We use it to infer the shallow acoustic impedance structure of the Tamu and Ori volcanoes at the Shatsky Rise oceanic plateau. Since acoustic impedance depends on the type of basalt present, the results allow estimation of lithology and, there- fore, insight into the late-stage evolution of both the volcanoes. Specifically, results from the shallow crust (~1 km) suggest a higher percentage of massive flow basalts at Tamu Massif compared to Ori Massif. The percentage of pillow basalts and geochemically altered basalts is higher at the summit compared to that at the flanks of the volcanoes.