Resolving Crust and Uppermost Mantle Structure beneath the Northeastern Corner of the United States Using Receiver Function Study

Abstract:

Teleseismic P-wave receiver functions are calculated with the water-level deconvolution method to image structure of the crust and uppermost mantle in the northeastern United States. Waveforms of teleseismic events from 1995-2014 are analyzed for a total of about 90 broadband seismic stations, including the EarthScope Transportable Array and long-running stations. A consistent positive Ps phase, presumably converted at the Moho interface, can be clearly observed at most stations. The Ps arrival time varies within 3-5.5 s, showing an increase from the passive continental margin to the eastern North American craton. Correspondingly, the crust thickens from 27 km to 45 km landward as inferred from the forward modeling of stacked radial receiver functions. A sharp Moho offset is observed across the state border from New York to Vermont and Massachusetts, which is expected at the transition from the older Proterozoic Grenville Province to the younger accreted Appalachian terranes. Nevertheless, no such pattern is observed beneath the northern part of the study area. A clear negative Ps phase is detected within a range of 6.5-9.5 s at most long-running broadband stations, which requires a sharp velocity decreasing with depth and may be generated at the base of the lithosphere. The arrival time of the negative phase gradually increases toward northwest, indicating the deepening of the lithosphere-asthenosphere boundary.