Mapping Deep Earth Interfaces Using Noise Correlations: A Step-Like Mantle Transition Zone Arrangement Beneath the Contiguous United States

Abstract Retrieving deep Earth seismic phases from noise correlations is hindered by the low amplitude of deep-path noise body waves. This study presents a data selection strategy that leverages quantitative noise phase composition analysis to enhance the recovery of faint body-wave reflections. Applying this method to noise correlation data computed across the contiguous United States, we successfully mapped the mantle transition zone (MTZ) discontinuities. We identified reliable P-wave reflections associated with the 410 and 660 km discontinuities within the 3–10 s period band. These short-period reflections reveal a pronounced step-like structure. Both discontinuities are deeper beneath the tectonically active western United States compared with the cratonic central and eastern United States (CEUS). Notable features include regions with a thickened MTZ beneath the CEUS and northern Colorado plateau, likely linked to the remnants of the Farallon slab. A region with a thinned MTZ is observed beneath the Rio Grande rift, possibly due to elevated temperatures caused by the release of volatiles from the Farallon slab. Our results highlight the effectiveness of noise correlation techniques in mapping MTZ topography.