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Seismic High Attenuation Region Observed Beneath Southern New England From Teleseismic Body Wave Spectra: Evidence for High Asthenospheric Temperature Without Melt
Author(s) -
Dong Mingduo T.,
Menke William H.
Publication year - 2017
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2017gl074953
Subject(s) - geology , attenuation , lithosphere , seismology , mantle (geology) , asthenosphere , shear (geology) , seismic wave , geophysics , petrology , tectonics , physics , optics
Seismic 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 < Q S < 25 , the ratio of P wave and S wave quality factors is Q P / Q S = 1.2 ± 0.03 (95%) , and the frequency dependence parameter is α = 0.39 ± 0.025 (95%) . The high values of Q P / Q S and α are compatible with laboratory measurements of unmelted rock and, in the case of α , incompatible with widespread melting. The low Q S 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.