Correlating crustal and lithospheric signatures with geological features in the central midcontinent from a high-resolution joint inversion of H-κ-c receiver functions and ambient noise tomography

Abstract:

Surface topography in the central Midcontinent of the United States, a region of North America's cratonic platform, has relatively low relief (generally < 300 m). This contrasts with the subsurface structural relief which delineates the boundary between the Ozark Dome and the Illinois Basin, as well as with recent studies emphasizing substantial variations in the depth to Moho, and in the velocity structure of the lithosphere. We present a higher-resolution reexamination of the seismic data that clarifies the correlation between the deeper crust and crustal root with geologic structures found in the shallow crust.

To examine the deeper structure underlying surface structures, we carried out a joint-inversion model incorporating both the H-k-c method and ambient-noise tomography. In order to properly address the trade-off between discontinuity locations and the velocity of the medium, both dispersion measurements and revised receiver-function calculations are used. Dispersion measurements are computed from ambient-noise correlations. The H-K-c method uses harmonic corrections to target plunging anisotropies and dipping surfaces in receiver function calculations.

We analyzed 333 stations from EarthScope Transportable Array (TA), as well as from the Ozarks–Illinois–Indiana–Kentucky Flexible Array (XO), the Wabash Valley Seismic Zone study (6E), and the Central and Eastern US Network (N4). The results provide a high-resolution tomographic model of the central midcontinent, encompassing the Illinois basin, the Ozark dome, the Ste. Genevieve seismic zone, and the Wabash Valley seismic zone.

Our preliminary results found correlations between Moho depth variations and near-surface geological features. Notably, the Moho beneath the central midcontinent is an undulating surface. As recognized by the OIINK research group, the greatest depth variation Moho depth significantly occurs across the northwest-trending boundary between Illinois Basin and Ozark Dome. The detailed velocity structure and Moho-depth variation revealed by our high-resolution tomography model will help test models for the formation of cratonic basins and domes in the central Midcontinent, and may provide insight into the Proterozoic assembly of the region's crust, as well as the region's contemporary seismicity.