Moho depth and tectonic implications of the western United States: insights from gravity data interpretation

Abstract

In this research, we figure out the lithospheric structures of the western U.S. and assess its tectonic implications with a high resolution using dense gravity data. Gravity data with high spatial resolution enables detailed mapping capabilities, overwhelming other geophysical data. To investigate the physical basis for support of topography in the western U.S., we employed the parker-Oldenburg algorithm to gravity to calculate the depth to Moho. The estimated depth to Moho shows an excellent spatial correlation with the physiographic provinces in the study area following an eastward thicking pattern. Moho of the stable craton reaches 50 km, whereas the western margin shows a shallow Moho of 20 km. Moreover, to assess the tectonic implication of Moho in the study area, we calculated the crustal compensation load to evaluate the isostatic state in the study area. The calculated compensation loads provide isostatic compensation for large-scale crustal structures, such as the broad, elevated Basin and Range Province. To assess the contribution of the crust and mantle to the topographic deformation in the study area, we calculated the crust topography and mantle topography. The Wyoming Craton and Great Plains have negative mantle topography values, contrasting with the relatively constant values in the southern Rockies, Colorado Plateau, and Basin and Range. Crustal topography reveals significant crustal support from the southern Rockies and the Wyoming craton. In addition, we estimated the lithospheric mantle thickness and the depth of the Lithosphere–Asthenosphere Boundary (LAB); the mantle thickness has values reaching 90 km at the stable eastern craton with LAB depth reaching 140 km. This research demonstrates the effect of the tectonic regime on the study area and the implications of this tectonic on the lithospheric structures with a high spatial resolution of a few hundred meters.