Mantle Structure and Flow Across the Continent‐Ocean Transition of the Eastern North American Margin: Anisotropic <i>S</i> ‐Wave Tomography

Little has been seismically imaged through the lithosphere and mantle at rifted margins across continent-ocean transition. A 2014–2015 community seismic experiment deployed broadband instruments shoreline of eastern North American margin. Previous shear-wave splitting along margin shows several perplexing patterns anisotropy, by proxy, flow. Neither parallel offshore fast azimuths nor null on continental coast obviously accord with absolute plate motion, paleo-spreading, or rift-induced anisotropy. Splitting measurements, however, offer no depth constraints Additionally, structure not yet in detail We used teleseismic S, SKS, SKKS, PKS differential travel times recorded ocean-bottom seismometers, regional networks, EarthScope Transportable Array stations to conduct joint isotropic/anisotropic tomography The velocity model reveals a transition from fast, thick, keel low velocity, thinned eastward. Imaged short wavelength anomalies can be largely explained edge-driven convection shear-driven upwelling. also find that layered anisotropy is prevalent anisotropic polarization within asthenosphere. This suggests flow beneath plate. lower oceanic preserves paleo-spreading-parallel while complex reflecting Wilson cycles. These results demonstrate active nature which traditionally considered tectonically inactive.