Multicomponent (pressure and three components of particle velocity)
data acquired at the seafloor allow the elastic wavefield to be decomposed
into its up- and downgoing P- and S-wave constituents. Most decomposition
algorithms require (i) accurate knowledge of the elastic properties
of the seafloor in the direct vicinity of the receivers and (ii)
properly calibrated sensors such that the data are a faithful vector
representation of the actual ground motion. We present a multistep
adaptive decomposition scheme with which the necessary information
can be obtained directly from the data by imposing adequate constraints
on intermediate results. A major advantage of the proposed scheme
is that there is no need for user-defined input or a priori information,
allowing multicomponent data to be decomposed in an automated data-driven
fashion.