THE ROCKY MOUNTAINS IN THE CONTEXT OF THE NORTH AMERICAN CONTINENT FROM JOINTLY INVERTED BODY AND SURFACE WAVE TOMOGRAPHY

The Earthscope USArray is providing an unprecedented dataset for seismic imaging. In this study, we rotate teleseismic body wave arrivals into the P-SV-SH coordinate frame to determine relative delay times and jointly invert the delays with phase velocity perturbations measured from surface waves generated by teleseisms and ambient seismic noise. We therefore parameterize the earth in terms of 1 P velocity model and 2 S velocity models, where one is polarized vertically and the other is polarized horizontally. Our dataset begins in early 2007 with the inception of the USArray-TA and ends in late 2011. This dataset covers the United States from the western edge, across the Rocky Mountains, and into the central US. DNA12 images the duality of the North American continent often seen in global models with a fast cratonic eastern side and a low velocity deformational region in the west with the dividing line along the Rocky Mountains. With the lateral resolution of body waves we image the key features in the western US mantle such as the sinking and breaking Juan de Fuca slab, the rising Yellowstone Plume, and dripping root of the Colorado Plateau. The shallow sensitivity of the surface waves from 8-125 seconds period provides information where body waves have few crossing rays and thus minimal resolution. The short period (8-30 seconds) phase velocities from ambient noise provide crustal information typically constrained only by local earthquakes and receiver function analysis. Therefore we image crustal features such as sedimentary cover in eastern Texas near the gulf, higher velocities near the Black Hills of South Dakota, and the sharp contrast between the rocky mountain front and the dust-bowl of the great plains. By utilizing multiple datasets to perform the joint inversions and parameterizing two independent shear models, DNA12 provides the must complete tomographic images currently available.