Lithospheric Structure of the Eastern North American Margin Resolved by Teleseismic Receiver Function Analysis

The eastern North American margin (ENAM) is an iconic passive continental margin, which records two complete Wilson cycles from supercontinent assembly to breakup over a billion years ago. Thus, it is an ideal laboratory to examine the orogenic histories and the lithospheric behavior during the multiple episodes of collision and rifting. With the eastward migration of EarthScope US Transportable Array and the recent ENAM Community Seismic Experiment, the broadband seismic data have significantly increased in this region, providing a great opportunity to investigate structures within the lithospheric domain. In this study, we use teleseismic P-wave receiver functions to image the lithospheric structure beneath the ENAM. Waveforms of teleseismic events from 2000-2017 are analyzed for a total of 890 broadband seismic stations, including 32 ocean bottom seismic stations. Consistent P-to-S phases converted at the Moho and the Lithosphere-Asthenosphere boundary can be clearly observed, showing substantial variations in phase arrival time from the Atlantic oceanic lithosphere to the North American craton. Correspondingly, a complex three-dimensional lithospheric structure is inferred from the common conversion point stacking. Our preliminary results show that the large-scale variations in lithosphere thickness roughly correlate to the major tectonic boundaries of the Appalachian Orogeny. However, the original lithosphere structure may be significantly modified at local scales by later tectonic processes, such as underplating and partial-melting. These receiver function results provide tight constraints on the relation between the modern lithospheric structure and the past tectonic boundaries, and thus significantly improve our understanding of the tectonic history beneath the ENAM.