CHARACTERIZATION OF CONTINENTAL CRUST BENEATH THE SOUTH-CENTRAL UNITED STATES USING REVERBERATION-REMOVED RECEIVER FUNCTIONS

P-to-S conversions (or receiver functions) from acoustic impedance discontinuities such as the Moho have been routinely used to delineate the topography of the discontinuity and other properties including the bulk Poisson’s ratio and the sharpness of the discontinuity. These observations provide first-order constraints on crustal evolution and basin formation models. Unfortunately, the receiver functions recorded by stations situated on a layer of loose sediments are pervasively contaminated by strong reverberations of the P-to-S converted shear-waves originating from the bottom of the sedimentary layer. The reverberations make it difficult to image the Moho in sediment-covered areas such as the ocean-continent transition zone (OCTZ) north of the Gulf of Mexico and the wide-spread sedimentary basins in south-central United States.

To effectively remove the reverberations, we have recently developed a resonance-removal filter (Yu et al., 2015, Journal of Geophysical Research, http://dx.doi.org/10.1002/2014JB011610 ) and applied it to several areas in south-central United States. Preliminary results show that the Moho can be reasonably imaged at most of the USArray and other broadband seismic stations. Systematic spatial variations of crustal thickness and the Vp/Vs ratio (which is uniquely related to the better-known Poisson’s ratio) are found. Significantly thinned crust beneath the OCTZ and the New Madrid Seismic Zone is revealed, while ancient collisional zones are associated with notably thickened crust. Details about the findings and their tectonic implications will be presented.