Crustal Thickness Variations in the Central Midcontinent, USA, and Their Tectonic Implications: New Constraints Obtained Using the H-κ-c Method

The central midcontinent of the USA's cratonic platform is a region of low elevation and relief underlain by tectonic basins, domes, faults, and monoclines. To investigate potential correlations among shallow crustal structure and crustal thickness, we produced a high-resolution Moho-depth map of the region by applying the recently developed H-κ-c receiver-function method to data from EarthScope Transportable-Array and Flexible-Array stations. Results indicate that Moho depth varies from 38 to 57 km. Changes of Moho depth and of Vp/Vs ratios do not correlate with Precambrian tectonic boundaries, suggesting that they reflect post-accretion tectonics. Deeper Moho underlies sedimentary basins, implying a relationship between crustal thickness and lithospheric subsidence. Thicker crust may be due to rift-related underplating, and thinner crust may have undergone delamination. Some depth changes underlie known faults and fold zones. Since short-wavelength undulations were detected only under high-density seismic arrays, they may occur more widely but have yet to be resolved.