Lithosphere-asthenosphere structure beneath the United States from joint inversion of body waves, surface waves, and receiver functions

The Earthscope USArray is providing an unprecedented dataset for seismic imaging. Many studies have generated models in terms of velocity or impedance contrast, but only a few are starting to integrate observations in a joint framework. The most common joint method inverts receiver function delay times with surface wave dispersion curves to image the crust and mantle lithosphere. Advances have also been made by jointly inverting surface wave dispersion observations with body wave relative travel times to image the upper mantle. These joint methods are producing clearer images and are fitting more observations than single dataset methods, however they do have their limitations. The surface wave and receiver function models are limited to the lithosphere while the body wave and surface wave models are inherently smooth which blurs the layered earth structure. By jointly inverting all three datasets we are able to image structure from the surface through the mantle transition zone under the Transportable Array footprint through July 2011. The stable North American craton is imaged at the eastern edge of the model as a thick high velocity body. The western portion of the model is largely slow through the thin lithosphere and upper asthenosphere relative to the craton. Within the asthenosphere, a 'slab graveyard' is imaged where broken fragments of Farallon slab reside. The Yellowstone anomaly rises amongst these slab pieces from the lower mantle to near the surface exerting control over local seismicity and topography. The Colorado Plateau shows signs of weakening of the lithospheric root resulting in removal by dripping. As a whole, the DNA11 model shows the mantle is far from a simple homogeneous medium.