Abstract
AbstractSeismic attenuation exhibits strong geographic variability in northeastern North America, with the highest values associated with the previously recognized Northern Appalachian Anomaly (NAA) in southern New England. The shear wave quality factor at 100 km depth is 14 < QS < 25, the ratio of P wave and S wave quality factors is QP/QS = 1.2 ± 0.03 (95%), and the frequency dependence parameter is α = 0.39 ± 0.025 (95%). The high values of QP/QS and α are compatible with laboratory measurements of unmelted rock and, in the case of α, incompatible with widespread melting. The low QS implies high mantle temperatures (~1,550–1,650°C) at 100 km depth (assuming no melt). Small‐scale variations in attenuation suggest structural heterogeneity within the NAA, possibly due to lithospheric delamination caused by asthenospheric flow.
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