Crustal properties beneath the northeastern United States shaped by past tectonic processes

Abstract

Constraints on the thickness, transitional boundaries, and composition of Earth's crust are pivotal in studying its formation and evolution. We use data from 132 seismic installations throughout northeastern U.S. to explore how tectonic events, such as orogenesis and rifting, have altered the crust of the northeastern U.S. and southeastern Canada, and to distinguish differences between Laurentia and the Appalachian terranes. We include data from seismic installations from the NEST and SEISConn experiments, spanning the Laurentia-Appalachian boundary, and present estimates of crustal thickness, Vp/Vs, and thickness of the transition between crustal and mantle rocks using Ps receiver functions. We find some first-order differences between Laurentia and Appalachian terranes, with Laurentia exhibiting thicker crust (∼39 km vs. ∼33 km) and a broader crust-mantle transition thickness (∼3 km vs. <1.5 km). Average Vp/Vs values are similar between Laurentia (∼1.77) and Appalachian terranes (∼1.74); however, we identify anomalous Vp/Vs in a few regions, including high Vp/Vs around the Adirondack Mountains and low Vp/Vs in southern New England. The southern New England region is also anomalous in terms of its systematically thinner crust and sharper crust-mantle transition, which may be a consequence of the formation and collapse of the Acadian altiplano during the mid-to-late Paleozoic.