Wave-Field Continuation and Decomposition for Passive Seismic Imaging Under Deep Unconsolidated Sediments

The coastal plains of the central and eastern United States contain deep sections of unconsolidated to poorly consolidated sediments. These sediments mask deeper crustal and upper-mantle converted phases in teleseismic receiver functions through large amplitude, near-surface reverberations. Thick sediments also amplify ambient noise levels to generally reduce data signal-to-noise ratios. Removing shallow-sediment wave-propagation effects is critical for imaging deep lithospheric structures. A propagator matrix formalism is used to downward-continue the wave field for teleseismic P waves into the midcrust and then to separate the upgoing S-wave field from the total teleseismic response of the P wave to expose deep Sp conversions. This method requires that the Earth model from the surface to the reference depth be known. Teleseismic P-wave data for the Memphis, Tennessee, station (MPH) are analyzed using a reference-station deconvolution technique to produce vertical and radial P-wave transfer functions. These transfer functions are modeled using a simple model parameterization for sediment structure through grid inversion. The inverted Earth model is incorporated into the wave-field continuation and decomposition technique to estimate the upgoing S-wave field at 10 km depth in the crust. Moho and possible deeper Ps conversions are identified with this process.