CRUSTAL STRUCTURE OF EASTERN CANADA AND NE USA FROM AMBIENT NOISE TOMOGRAPHY

Eastern Canada and the northeast USA record a complex tectonic history. Studying the seismic structure beneath these regions will pave the way to address many unanswered questions about the past tectonics. With the aim of resolving crustal structure of the northern Phanerozoic Appalachians and the southeastern Proterozoic Grenville province, we apply ambient noise tomography to data recorded in 2013-2015. Our datasets include continuous timeseries of more than two years of ground motion recorded by vertical components of 69 stations belonging to 7 different networks. The resulting waveforms, arising from stacked daily cross-correlation of station pairs, suggest that the distribution of noise sources is neither stationary nor isotropic. Therefore, we perform directionality and seasonality analysis on our datasets and discuss the results. Clear fundamental-mode Rayleigh waves are observed at periods between 4 and 60 seconds, covering depth sensitivities from the upper crust down to sub-Moho depths. We use a recently-developed method to measure phase velocity curves for a selection of inter-station paths in the spectral domain. The resulting dispersion curves then are used in a tomography approach to determine anisotropic phase velocity maps at different periods. We investigate the correlations between phase-velocity variations and surface geology to discuss the regional structure and its tectonic implications.