Multi-scale imaging of 3-D electrical conductivity structure under the contiguous US constrains lateral variations in the upper mantle water content

The magnetotelluric (MT) component of the USArray survey is a unique data set that enables imaging electrical conductivity distribution from surface down to astenospheric depths. Here, we present new 3-D model (MECMUS-2022) derived by inverting 1291 MT stations covering ∼80% contiguous United States on quasi-regular 70-km grid. inversion was performed using novel multi-scale approach can consistently incorporate large range spatial scales and perform modeling directly in spherical frame, completely avoiding conventional flat-Earth assumption. Furthermore, use locally refined meshes allows us take into account complex coastline mimic natural resolution footprint broadband transfer functions. We find variations correlate with known continental structures such as due active tectonic processes within western (e.g., Yellowstone hotspot, Basin Range extension, subduction Juan de Fuca slab) well presence deep roots beneath cratons. further interpreted terms upper mantle water content coupling constrains thermo-chemical structure analysis seismic (in form P-to-s S-to-p receiver functions). Our results suggest existence relatively dry States, weak trend North South.