MANTLE HETEROGENEITY OF CENTRAL AND EASTERN NORTH AMERICA COMPARED TO THAT OF WESTERN NORTH AMERICA

Continent-wide geophysical studies have long pointed out differences between tectonically-active, western and stable, central & eastern North America. One well established difference is between the low average upper-mantle seismic velocity of tectonically active North America (taNA) and the high average upper-mantle seismic velocity of stable North America (sNA), ascribed predominantly to an upper-mantle temperature contrast of many hundreds K. Another such difference is the finer, more abundant detail imaged beneath tectonically active North America (taNA). However, teleseismic delay times recorded by USArray and its predecessor seismic arrays tell a story of similar diversity in mantle structure beneath the contrasting domains. While prominent surface geology often correlates with clearly anomalous mantle structure in taNA, such correlations are not typical for sNA. This difference is owed in part to less abundant sNA data providing reduced resolving power and in another part to the older ages of the Precambrian sNA geology. To differentiate between these two causes and to address the diversity in sNA mantle structure, we test existing seismic-tomographic models against two new datasets: 1) teleseismic delay times at arrays of seismic stations east of the Rocky Mountains, and 2) regional wave trains at USArray stations in sNA from fortuitously contemporaneous earthquakes in sNA. Recent, current, and the near-future completion of USArray's Transportable Array's deployment on the eastern North-American margin will allow further verification or falsification of these results. We conclude by focusing on the Mid-continent Rift System as a particularly prominent geologic feature in sNA. To date, data from an ongoing dense Flexible Array seismic deployment (SPREE) do not show a convincing correlation with mantle heterogeneity and will be discussed.