Ambient noise Rayleigh wave tomography in the lithosphere of a southeastern U.S. continental suture zone

Abstract:

Constructing a high-resolution seismic model of continental suture zone structure will place new constraints on lithospheric deformation processes. The Southeastern Suture of the Appalachian Margin Experiment (SESAME) deployed 85 stations across the suture zone between Laurentia (proto-America) and Gondwana (proto-Africa/South America). SESAME stations, together with 62 USArray transportable stations also deployed in this area, provide sampling of unprecedented density.

We use vertical component data from SESAME and USArray stations operated from 2011 to 2014, resample to 10 Hz, and compute noise cross-correlation functions (NCF) for each station pair on a daily basis at four different frequency bands within the period range of 5 to 30 s. Noise cross-correlation functions are stacked over 4 years and Rayleigh wave dispersion curves are measured using a phase-matched filter, frequency time analysis technique. We estimate measurement uncertainties using the seasonal variation of the dispersion curves revealed in three-month stacks. We find strong source directivity caused by ocean-wave-generated noise and estimate the 2-D noise source distribution using groups of stations. With the estimated noise source distribution, we correct the strong asymmetry of the NCFs to reduce the bias in phase velocity measurement, and produce Rayleigh-wave phase and group velocity maps at periods from 5 to 30 s. Ultimately, we aim to construct a regional seismic model and interpret the final model in terms of temperature, composition and rock deformation fabrics for a better understanding of the deformation history of the suture zone lithosphere.